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MICROCOPY RESOLUTION TEST CHART
MICROCOPY RESOLUTION TEST CHART
NAIIOMl BUR[/\ll
or
SlAND'RO~·I96J·A
NATIONAL BUREAU
or
SlANDARD,,19&3·A
,
-Ii "'~'~m'=~'~~i
7
TECllNICALBuLLETIN
No, ,64
,"
'
"
2
MARCll,l928
UNITED STATES DEPARTMENT OF AGRICULTURE WASHINGTON, D,C. BACTERIOLOGY AND CHEMISTRY OF OYSTERS
WITH SPECIAL REFERENCE TO REGULATORY CONTROL OF
PRODUCTION, HANDLING, AND SHIPMENT
By,ALllEIIT C, HUNTKu, .!l.~.~oai(lt(J Ba.oterioloyi8t, und OHANNING W, HARRISON,
Oh,fcf, jli1tIlCaPOU,~ Stlltion, Rood, 1)r'rty. (lc/Hi J./lseaUvide A.d/l~iniat"a.tiQ/i 1
CONTENTS
Introductlou ____________________ _
:Phe oyster Industry_______________ _
Chemlc!'1 cOll1[losltion of oysl~ ..s ___ _
Ments nud litJuur____________ _
Shells______________________ _
Physical
nnd____________________
chl'lIllcnl cXtllnlnntlulI_
of oysters
Oysters ns cn....lers or Infectloll ____ _
Bllctcrlologlclll
clCnIllinutlon or oy~tc.. s __________________________
_
Stnndnrd method ____________ _
Pollution of oyster lIed8__________ _
Bacterlnl
florn of nnpolluted
oysters___________________
_
Bnctcrinl
!lorn of poilu tl:d oys-_
tcr8 ______________________
VILlblllty of B(/l'illll~ tll/l/WOIlH
nnd
B. (Joli in oysterH nllli
wuter____________________
_
Ell'ect of cooking on lInct.el'lal r~ontent of oyste..s ________________ _
Hestride!1 OyNtl~I··llI·"(\uciu,; 1lI'l'lI~ __ _
IIlbm'ulI tlO1I of vyslcrs___________ _
rng-I!
1
2
;I
4
11
10
13
15
15
18
18
18
l.'uriflcn tion of oysters____________ _
'so
30
:i3
~1',.anBpiuutiu;;---------------Chlorinntlon
________________ _
Fiolltiug oysters in the RheIL _____ _
Shuckin'g-house sanltntion ________ _
Wnshlng oysters_--______________..:
In 'th,l sheIL________________ _
Out of the sIlIlIL ____________ _
1~ll'ect
on \-olume nlld composi­
tion __________________'
_ __ _
Whnt
constitutes
I;ood
wnshhlg_
Shipping oystel's _________________ _
·43
43
44
Cause of decomposltion-------Rllte of deconrpositioll ________ _
ni~tection of spoilagL________ _
l'.revelltlon of sllollnge ________ _
i;!I;"lI!ficance of .. .free liquor"__ _
o)'ilh'I'S ___________________ _
Color€ d by coPPeI' ____________ _
58
60
61
62
64
GI'G!~n
11)
.Poge
Green
~[Iled
_________________ _
.l'lnk oysters____________________ _
Olpuphl oystl'rs_________________ _
Utcl'utul'e clted_________________ _
36
41
47
a5
57
57
,64
66
66
68
70
INTRODUCTION
The production, hundling, and shipping of oysters were always of
interest to the Bureau of Chemistry in its enforcement of the Fed­
eral food and dl'lwS act, The ])ossibility of pollution with sewage
and trade waste, t~e l'U pidity with which spoilage takes place when
1 The writers nre pnrticnlnrly indebted to Pnyn B. Pm'sons, formerly o( the 'Burenu or
Chemistry, now with the NeW 'york State Conservlltion Commission, for lOnny lIuggestions
nnd mUch mnterlnl, especiallY Oil t.he bacteriology of oysters. H. D. I'l'lIse, of the I'ense
Luborutorles, F. p, Gorham, of Brown University, nndL. A. Itound ulld S. DeM. ,Gege,
both Ilr the ,Rhode lslnnd Stnte Bonrd of Henlth LaborntOl'ies, bnve vel'Y kindly helped with
suggestions lInd ndvice. H. W. llnlcom, ot the Food, .o1·ug; ulIll Inspcticide Admlnistrntion,
118sisted in plnnning allll prepnring tht' bulletin. l~innUy, ncknowl(l(lgm'lnt is mnde tu a
IlIrge numher of individunls in the service whose Identity could not he learned from ·the
omclnl repul'ts ,of thcir analvses which IIllve heen ,\lsed In this 11IIlIetin.
Altbougb this bulletin Is 'published nHel' thl' eslnhliHhml.'1It of the Bureau of ChemIstry
nnd Salls nnd the I~ooll, Drug, 1111(1 rnsectlclde Admin!Rt\'lltion, it iN n contribution ,from
the old Burenu or Chcmil;try I'Ilther thun from either of the two new units,
7SI){)ijO-2S--1
1
2
r
1!
ffi
\TlilCITNIOAL BULLETIN 64, U. S. DEPT. OF AGRICULTURE
oyster~ nre Imnc1iec1 improperly, and the likelihood of adulteration
with water dul'ing the wasl1ing processes have made. necessary exten~
sive biological und chemical investigations to obtain the .infol'ma­
tion l'equil'ed to establish l'egnlatio.ns controlling the shipment of
oystm's in interstate commerce. The Federal food nnd drugs net
(91) ~ is lLpplicable to oysters in that it defines !ldulteration
as ((t) the llIixing of any substance with a food pL'oduct so as to
reduce or lower or injuriously affect its quality or strength, (0) the
substitution of !lny substtmce wholly 01' in part for the article, (0)
the removal of !tny vuluubl(} constituent wholly or in part from the
food product, (d) the presence of any poiscl!1oUS or other added
deletet'ious ingl'edient which rende/'s the food injurious to he~tlth,
und (e) the presence of any .filthy, decomposed, 01' putrid animal or
vegetnble substaIlt:e, DeHnitions of misbmnc1ed products given in
section 8 of the aet HI'C particularly applicable to cnnnedoysters.
To obtaiu rdillbIe data upon the mllny biologi.cal and chemical
problems SlU'l'OlUHILng the production and shipment of oystel's, upon
which to ,base intel'\)l'etations of the :food and ch'ugs nct !lnd rulings
that are Just to bot! the Pl'Oc!UCC1' !llld the consumer, the 13ureau of
Chemistry conducted muny investigations to determine the biologi­
cal pl'in:iple, ; ~ self-plll'ific!lt~on of oy~ters, th.e purification b'y tJoeut­
ment With culcn\ln hypochlorIte, the lubernahon of oysters, and the
effe~t.of vlu'i<?lIs methods of washin~ !lnd shipping.
'.
..
'Lllls bulletm presents u slll'vey of tbe results of sllch lIlvestlglLtlOns,
supplemented where necessary by references to the finding::; of other
investigators.
THE OYSTER INDUSTRY
Mollusks of the group tlUlt includes oysters arc ClLlled bivalves,
becllllsP they have two shells 01' vulvl"s, Oysters of commerce belonlY
to the genus Ostrea, a great many species of which are grown i~
vIll'ious p!lrts of the wodd. Thus the oyster produced ill Europe
is the Ost'l'ca ed1tU.~ nnd the principal species in Japan is the O. ou­
oullotll. Two species are found on the ~oa~ts of Mexico, O. elon,gata
on the castel'll const nnd O. cohtlnbzol/,8UJ 011 the western coast.
O. 1melclwna is produced on the eustc.rn coast of SQuth America and
O. colunnbiemri$ and O. cMleruJ'w on the western COIlSt. Other species
runge from Norway to Chile and New Zealand.
In the United States the principal oyster of cormnence is the
Atlautic and Gulf coust oyster, O. vi?'ginioa. 'fhe smull Olympia
oyster, O. lwriila, is grown in the waters of the Pu,cific Northwest,
especiully in nntl about Puget Sound and 'ViTIapu Hurbor off the
coast of \Vashington.
Oysters nre produced commercinlly jn all the Atlantic !lnd Gulf
COllst States except Muine and Now Hampshire. On the Pacific
coast, Oregon, vV!lshington, and California produce for the market
eit:ler the native Olympia oyster 01' the eastern oystet, and some­
times both (55).
Chure-hill, in discussing the geographical distribution of oyster­
growing areas,hns c1escl'ibed in some detail the sections where oYRtel'S
• Reference Is nUlllc .1Jy ItnUe numbers In pnrenthcsls to .. L1ternture cited," p, 70,
3
'BACTlnRIOLOGY AND CilEMISTRY OF OYST:ElRS
nre grown (136). Most of the oysters on the Atlantic and Gulf
coasts are grown in, rivers n,nd bays, and in coves along the shore.
The methods of cultivating, harvesting, and hanclling oysters vary
somewhat in the different regions. In certain sections oyster beds
Ilre leased from the State ,and the oysters are cultivated by the
lessee. In other sections oysters grow naturully on beels or reefs anel
enn be taken by nnyone ,,,ho has the proper license, Different types
o:f genr are used; different chl5sesof emp10yees are hired to do the
wo11(; di:fferent shucking and washing methods exist. Furthermore,
the conditions of pollution nxe different in vurious ]ocnlities 11llc1,
owing to the difference in the salinity of the 'waters, there are differ­
ences in the chemical composition of the oysters. No Olle investigatj:)n
to fix regUlations controlling the oyster industry ClLn !tlJply to all
localities. It has been necessary to make extensive studies of eonc1i­
tions in all oyster-producing regions in order to l'euci:, just decisipns
IIpon regulatory matters.
The methods of gather,ing, storing, shucking, wuehing, and market­
ing oysters are elesel'i~cdin detnil by CllUr~llill (l36). Although
oysters are usually sluPIJecl raw, some 1\,I'e canned. Cnnned oyster
juice amI dried oysters lire sold in limited qUllntities.
The total production of oysters for the madcet in the United States
H'llches severnlmiUion bushels nnnually. Statistics llre not In'aiiable
fOl' the oyster ('rop for the United Stutes for nny one year. Table 1,
whieh gives the number of bushels of oysters grown for market by
each producing State on the Atlantic, Gttlf, a.nd Pacific coasts, shows
that Maryland lind Virginia, drawing upon Chesapeake Bay for
their supply, produce many more oyster's than any other region. The
Pacific coast production a.ppears to be rather .snmll as compared with
thut of some of the Atlantic and Gulf coast regions.
1\\IILE
i.-Oll,vtor proeT.llClion of tlle United, HinteR 1
Stllto
A1111ntio COllst:
l'vI1\S.'II~husotts
.__________
Rhode Island s___________
OOllllecticut ,____________
QUllnUty'
"nluo
Stnto
JJIl.,hel.,
110, n02
8\14. f';17
lJal/ar.'
2711, M7
1,2,12,585
GIIIIAconaL:
IlIhl1lnll , ______________ _
709,04U
40a.1l1l1l
Now York ,______________ I, :J.lU, 211l I, 77,~. 45:1
Nu\v J",rsoy ,_____.. __ .. ___... 1,578, 105 2. OiO,.JUO
.oelnwnro , ______________ )
,101,826
a08,115
Mnrylnnd ,______________ ·1. f,I7, >171 . ,2, 2111, Il!t)
Vlrglnlll'________________ a, 2'25, S.J.I. i 2. 1117.112:1
I
North ('lIrollnll ,_________
South Cnrollnn ,__ ______
Ocorgiu
4~ ____...... _ .. ______ ..
MIl.028!
718,OOtI I
245,7U2
I
2'2\), mil
113,1155
80,771
Quantity,/ Vnlue
Atlnntiu
nnd, _______________
Gulf cOlISts:
Florhlll
_ .B".,lul.,
3C1~ :~14
OSO
Mississippi , ____________ _ I, 233,
60n. ,122
Louisinun 8.. _____________ _ 1,022, Hill
..c; 6____________ _____ _ :UiU,078
PnclWlIshingto;!
nIl "nllSt:
, ___________ _
~rel"n
~
Oregon , ________________ _
Cnllfornla , _____________ _
110.484
10,714
la,fiU
,Dallar6
,86,31l9
86.719
,1.72, 052
770,434
170,076
308.4fl.1
7,500
101,351
I Stllt,lstics furnished hy Dllrellu of L'llihories, U. S. Depllrt munt of Commerce, 'This represonts ,llUlrket oysters. It Is exclusive of seed oysters produced. > }o'or 11l10. I For 1021. 'For 1020. • For 1923, 'For 1m. Table 2 shows the number of cases of canned oysters produced by
various Stutes in 1924, with the total value of the output.
4
TEC~ICAL :BULLETIN M, U. S. DEPT. O:E' aGRICULTURE
: ~l
TADUI!l
2.-N11m.bcr of ca,llc,q·· cmel '1'llluc ,ofca,nnccl o1lsters' produccd ,in ~1te ,UlIi.ted
Statcs 'in 1lJ2.it un)
,Cuns .In eadh ellSo
Num. Mnry.1 North
Curober 'lllnd
Una
Sizu
----·1---·OU11ct8
South.
Aln. M"
Loulsl·
15S'S' nnnnnd Ons::!!
Cnro· GeorgUl .Fioridn b ,m.l
Una
•
sippi '£exns
Value
- - - - - - --------.-- ---
48, .7,343
Otl8 112,855 '_."'" ................ 32, O?~'i ........ 52.901 $262,432 .18140,715 32,221 72,:187 12,120 12,6OS 9,922 120,189 7,58.'i 307,747 1,652,810 '\8
7,68·\ ........
104 __...... ........ ........ ........ 2,000 1I,78B
97, OS6
2·\
3,138 ........ 2,195 ........
278 ........ 10,730 ........ 22, au 110,55:;'
4. __._._.....
n. __ .........
G._..........
8........... _
~g:::::::::::
Tota1....
~otal
NumbOr or ClISes produced in-
~1
i
I),
W~
..~~~~~..:~~:~:...__ ~~~.....~~....~.:~..~:::~~. ::::::::
06, ~~~
34~:~
=(IiS;o05 3G.857 Ui3,808~ 13.280 ll,422 204;&i8 ~ 4iiii:4212.478.1i«
I Oysters woro cnnnml nt 0 (,Iants In Mnrylnnd, 6in North Carolillll, 131n South 'ClIrolina, Gin Georgia,
61n ]'Iorldu, 5 In Alubl\lllll, 2L1n :MiSSiSS;Ppi, 6 [n Lonisinnll, nndl in Taxus.
'Includes puck of 3·0unce cllns converter to the oquh'ulcnt of 4·ouuco cans, 4 dozen to the case.
In order to indicate the l'ela':/;lve value of the oyster crop as com­
pared with that of the entire fisheries output of each oyster pro·
dueing l'egion, Table 3 has been compiled. In compiling the data for
this table oysters from private beds and from public beds were added
together. No oysters produced for seed were considered.
TAIIL1!l
B.-Oyster outllnt (wd total fisheries
..
StnttlS
Yoar
MtI55llchusetts, !thode Is·
landy'lUd Conuectkut•• 1019
New' ork, Now Jersoy,
and Delnwllre __........ 1921
Marylnnd nnd Vlrginh, ... 1020
North Carolina, South
Carolina Qeorgla, and
Florid" ?enst eOllSt)..... 1023
'P'lorldll (west eOllSt) , Ala·
bBIlln, Mississippi, Lou·
Isiana, and TOxllS__ • __.. 1923
WlISbington, Orogon, and
Callfornla.__........... lU22
OUtlJ'ut
bII
8CCtiOllS
1
"
~'otlll
fisheries
Pou1/(!a
Part
Oysters t
Pot!1Ui8
31S,8M,771
11,000,715
332, 337, 120
530, 749, 884
23,233,401
64,413,205
repro·
sonted by
oysters
Per cent
3.8
Totnl
value of
fisheries
Dollars
Vnlue
Vnluo ot
reprooYSters sented by
oysters
Dollara
Per cent
15,856,062
2,015,798
7.0 11,022,172
10.3 12,740,302
4,214,004
4,450, ot3
12.7
30.2
35.0
5,OS7,340
448,137
8.8
228, i47, 930 11,172,336
4.0
24,823,300
15.5
8,006,050
1,574,445
19.4
592,084
.2
12,083,583
417,314
3.2
160,324,012
232, OOS, 421
~
I Compilml from U. S.Dept. Commorce, Bur. Fisheries Stilt. Buls. (o,e, OS, 04, 05, 96, OS) •
• Market oysters, exciusive of seed oYSters. Inciudes both ensteru nnd nnti va oyste~. I
CHEMICAL COMPOSITION OF OYSTERS
MEATS AND LIQUOR
Very few results showing the exact chemical composition of oys­
ters are available. For enforcing the Federal food and drugs act
and for studying the chnnges that take :place during floating (p. 36)
and wRshinO' (p. 43)., it 11ns been suffiClent to determine the solids,
ash,and sart content. A lal'ge number of analyses indicating .the
proportion of solids and salt In normal oystel's from various locali­
ties are therefore at hand.
From the few detailed analyses available it is evident thnt oysters
are very complex bodies, high in nitrogen and phosphorus·contain­
.}.,,'
ing :compounds. Rodoubt, both water-soluble .and water-insoluble
pi'()tein$are present. Carbohydrates, in the form of glycogen; are
found in varying quantities. Oysters also contain fatty bOdies,
'which are usually reJ?orted as "ether extract." The .ash of oysters
,.contains, besides sodlUmchloride,probabll :almost every chemical
element of sea water. Iodine and traces 0 bromine are 'present, as
well .as calcium and magnesium carbonates~
According to an anonymous review (1), the average weight ot the
native English.oyster is 142 grains, the moistpre content is between
77 and 83 per cent, the oyster ,contains organic matter up to 21 per
cent, and the mineral matter content is between 1.6 and 2.5 pet' cent,
Protein constitutes 46.3 per c()nt of theot:ganic matter examined,
glycogen being present to the extent of 4 per cent, and the fat con­
tent is 4.7 per cent. The rest of the organic portion is composed .of
nonnitrogenous matter. Glycero-phosphoric compounds, such as
lecithin lind glycero-phosphates of .alkali metals are present. Fifty
per cent of the mineral matter is composed of soluble phosphates and
32 per cent is. sodium chloride. There are smaller proportions Qf
magnesium and calcium phosphates, with traces of copper, zinc, and
other metals.
Mitchell (6!Y) reported that the carbohydrate glycogen is the
substance the presence 01' ubsence of which makes oysters fat or lean.
He found that the proportions of glycogen in 32 determinations
varied from 3.05 to 22.46 per cent of the ash-free solids. )Vhen
food is scarce oysters use glycogen to spare the proteins..
In analyses of dried samples Hindman and Goodrich (45) found
that 7.4 per cent protein, 1.62 percent fat, 2.12 per ·cent ash, Ilnd 3.2
per cent carbohydrate were present in Atluntic coast oysters; and
7.58 per cent protein, 1.64 per cent fat, 2.07 per cent ash, and 3.4 per
cent carbohydrate in Puget Sound oysters. These data are in ,good
agreement with the results of analyses mude in the Office of Experi­
ment Stations, United States Department of Agriculture (13), which
showed that oysters contain 13.1 pel' cent solids, 6.2 per cent protein'.
1.2 1;>er cent fat, 3.7 per ·cent .carbohydrates,.and2 per . c ent ash.
MaXImum, minimum, and:t.verage figures from the very large num­
ber of analyses made by t.he Bureau of Chemistry (Table 4) show
the rllnge .of solids, ash, and sttlt in oysters from known sources.
....
"
TABLE
0).
4.-Solids, cuh, and salt content of authentic samples of oysteT8
~;~,:ats
Source and condition of oysters
Meat
Liquor
Liquor
Entire sample
1---;-----.----- ----,;-----,---- - - - - , - - - - , - - - Solids
Ash.
Salt
I I
Solids
Ash
Salt
I
New England:
Unwashedcent Per cent Per unt Per crot Per cent Ptr crot Per Ct1lt. Per cent
Maximum ,__________________________________________ _ P..
2-1..4(26) 24; 05(20) 3.03(15) 1.41 (20) 6.67 (20) 2. 76(15) 2.66(20)
Minimum ___________________________________________ _ 95.7(20)
75.6
4.3
16.94
1.84
.67
4.60
2. 40
1.81
A verage _____________________________________________ _ 85. 07
2. 29
5:32
H. 93
20. 57
.92
2.57
2.13
WashedMaximum ' ___________________________________________ 1 98. 5(15)
1.56(15)
.63(15) 7.00(15) 1.72(9)
13.9(15)121. 44(15) 1. 99(15)
Minimum__________________ _________ __ __ __________ ___ 86. 1
1.5
15.29
1.20
.24
.40
3.62
1.08
_...verage_ __________________ ___________ _____________ ___ 93. 1
1.50
.35
6. 9
18.20
5.01
1.34
.97
New York:
UnwashedI
tiFnI:::~:::_':::::::::::::::::::::::::::::::::::::::::::
~: 1(15)
A "eroge__ ______________________ _______ ____ ___________ ::::::::::
__________ ::::::::::
__________ 20.0
I
WashedMaximum ,_______________________________________________________________ 19.2(15)
Minimum ________________________________________________________________ 13.6
A vcrage_ ______ ______________________________________ _ __________ __________ 17.3
Delaware Day:
Unwashed­
~1¥!a~~:':==::============:==========::=====:======= ==:=:~====I=====::j .~: r
4
Wnsi\~num ,_______________________________________________________________ /18.69(3))
2. 90(15)
1. i3
2.19
1. 72(15)
.98
1.29
2.10(7)
1.74
1.92
~\~~~~~:::::::::::::::::::::::::::::::::::::::::::: ::::::::::1:::::::::: iU~
Chesapeake Bay:
UnwashedMaximum ,---________________________________________
97.0(22)
i~~::~~:::::::::::::::::::::::::::::::::::::::::::: ~g: ~
Washed100 0
Maximum
Minimum___________________________________ _________ !lO.. 0 (27)
A verage_ _________ ____________________________________ 95.4
Bouth Atlantic and Florida:
UnwashedMaximum ,__________________________________________ _ Mlnlmum___________________________________________ _ i6.6(5)
A verage_____________________________________________ _ 52. 5
'-------------------------------------------1
74.6
r 40.0(22) 126. 9(35)
I 1~: ~ . ~~: g
2.25(35)
.93
1.36
10.0(27) 117.5(27)
.0
10.73
4.6
14;18
1.35(13)
.76
1.01
47.5(5)
13.4
25.4
2.72(5)
.80
1.38
18. 33(5)
14. 28
15.70
Solids
Ash
PerctTll
Pa cent
21.58(20)
15. 55
18.29
21.0(15)
14.41
17.28
Salt
1Per ctnt
2. 70(15) 1.53(20)
L97
.80
2. 25
11.10
1. 77(9)
• M(15)
1.25
.27
1.44
.40
1:. ~(15)
::::::::::
:::::::::: :::::::::: :::::::::::: :::::::::: ::::::::::
i3
______________________________________________________________
.34(15) ______________________________________________________________
.09
_____________________________________________________________ _
.16
___________________________________________________ '- ________ _
.67(14)
.09
5.06(3)
3.93
.44
4.46
j ~.18(3)
1.92
2.07
2..64
00(34)
1.22
.28(27)1 5.96(18)
.00
2.38
.08
3.84
1.31 (12)
.64
1.14(5)
.05
.36
4.01(5)
2. 56
3.20
.78
2. 58(5)
.59
1.20
t!J
o
~
!2l
....
o
E=i.
b;j
c::
~
1-3
~
~~,
~
f1l
1------------ _________ J________ _ ''tft!J='
1------------ ----------1--·------­ !"3
1.62(3)
.89
______________________ 1_________ _
1.32
:~(" ::::::::r:::::::::::::::::::::::::::::: ::::::::::1'==:===:=:=
I 11.
---------- ---------:
.74(32) 1 6.65(34)
.02
2.90
.20
4. 03
1-3
52(34) I---------~-. 34
___________________________ __ _
.89
.._____________________ 1.._______ _
~~
1.05(IS)
.18
.40
16.47(9)
9.98
13. 00
.13(9)
.03
.06
2. 05(5) .38 ·dl3
... ::..-- __ - ......... -1- --- .......... -";I--!>--.... - __ o
1:1:1
...
§
.....
o
g
1-3
~~
was:f!imum,
'------------------------------------------1 ~.
0(7)
!;~~~~::::::::::::::::::::::=:::::::::::::::::::: 8~: I
Olympia:
Unw8sbed­
1.faximum , ___________________________________________ l\ffnimum____________ •_______________________________
_>.. vemge_____________________________________________ •
Eastern oysters transplanted to Pacific coast:
Unwasbed­
1.!axlmum , __________________________________ •________ 1.1inimum____________________________________________
A vemge __________________________ • ___________________
I 20.9(7)
1
g l~: ~
17 47
. (7)
It
I
1.72(7)
j I: ~
I
.0
.47(7)
.16
1
r .37
62(7)
.86
I
I
4 57
2.
. J4 (7
3.23
I.
78.0(14)
56.2
64.7
43.8(14) 24.46(14)
22.0
20.10
35. 3
22.84
2.74(14) 1. 43
1.00
.60(14)
.17
.35
93.3(5)
54.4
74.0
45.6(5)
6.7
26.0
2. 42(5)
1.60
2.05
.82(0) 15.00(5) [ 2.59(5)
.51
3. 92
2.22
.64
~~
2.~
22.26(5)
19. i7
20.80
4.41 (5)
3.91
4.14
II.
I------------l----------!---~-----
.27
26(7) ______________________ '_" ________
.60
______________________1-_________
2. 72(14)1 2.15(14)
1.67
.1. 27
2.32
I. i9
I
2.29(5)
1.80
2.~
I n. I
20.56(6)
9i
15. 02
I
20.56(5)
13. 46
16.59
2. 63(6) 1l.47(6)
I. 46
. 59
2. 40
22
I.
I 1. 46
2.43(5) 1 1. 33 (5)
• 59 1.96
.99
I Tbe number of determinations from wbicb the maximum, minimum, and average figures in eacb case are taken III given in parentbeses after tbe maximum tlgure.
..
~
1-3
t1;l
I
~
Cl
~
Is:
til
~
.:;}
o
~
~
m
.~
"
,",
8"
TEOHNWAu BULLETIN64JU~'S. DEPT. bF'AGRIOUllTURE
The solids content of northern oysters is higher than that of
southern oyst,ers. 'rRe moisture content of unwashed oyster meats
varies between about 73 and 85 per cent, making them from three­
fourths to four-fifths water. These maximum Ilnel minimum, figures
may not be absolutely the highest or lowest which might be found.
Oysters often contain appreciable quantities of heavy metals.
Many investigators have reached the conclusion that all oysters con­
tain some copper. According to Hiltner and Wichmann (44-),
zinc is present uuiversally in oysters, at least in those grown in
Atlantic waters. These investigators state that there is no direct
relation between the zinc content and the body weight of oysters, no
uniformity of ratio of zinc to copper, !lnd no correlution between the
zinc content of oysters and the wnter in which they grow. The
,quantities of heavy metals present seem to indicate that oysters exert
a selective action for zinc and copper. The high proportIOns of zinc
an;d coppe,'r in oysters from be.ds III the vicinity 0'£ ind~stria! plants
usmg these metals can b~ rendlly accounted for. rhe hIgh ZlIlC con­
tent of those from beds iar removed from any known source of metal­
lic contamination mny be explained by the probability that oysters
~radually remove traces of the metals from the ,vater imd store them
1Il their tissues.
The arsenic, copper, zinc, aud le!tel contents of oysters taken from
beds, mostly in t.he vicinity of New York and New England, were
determined. (Table 5.)
TAIlLE
5.-JIcII'I-'lI met(a con/.ent of {}ystersof known origin
Source
Dllte exnmined
1917
Connccticut:
MimlUs Hi \'er___ ._ •______________________ Jlln. 18
Mouth 01 Minnus Rh·or _________________ Jlln. 30
NewPrincCllS
York: BIIY____________________________
Fob. 0
}'eh. 21
}'ob. 19
Mur. 2
Greenport, j.ong 181111Id .. ________________ l'eb. \l
Oyster BIIY, Long Islnnd ________________ Feb. 13
Mllr. 0
Grollt South nIlY________________________ Feb.
14
Mur.26
1I1nr.27
Oyster Uny, Coid Spring Iltlrbor________ Feh. 14
East Rocknwny _________________________ ___ do ____
Rocknwny_________________ -- --- -- ------- ___ do ____
Hempsteud BnY_________________________ Feh. 15
lI1'nr. 20
NewPerth
Jersey:
Amhoy. __________________________ Feb. 21
Virginiu:
Wachuprenguo __________________________ Mur.13
Arsenic
(As.O,)
Copper
(Cu)
Zinc
(Zn)
Mom. per
Mom. per
Mom. per
kilo
{
1.5
1.4
2.2
1. Ii
3.0
1.6
1.4
1.6
.6
kilo
30
Lead
(Pb)
kilo
2,419
4
ISO
1,936
117
1,403
2·15
2,022
1,3f)7
1,357
:202
1M.
67
136
1Q6
l,S511
Trace.
Do.
Do.
Do.
US
IS
886
1,274
1,.734
1,107
886
71
1,430
SIO
1,846
1,066
1,222
Do.
Do.
41
45
3.5
2,118
3,107
Do.
2.4
12
394
.S
.8
2.2
1.8
1.0
1.2
1.0
.6
1.6
19
47
47
605
Do.
Do.
All the samples contained appreciable quantities of arsenic, copper,
and zinc, and some showed tl'ltces of lea~. The zi~cc<?nte~t was vel:y
high. It WitS easy to tl'ltce the metallIC contammation msome of
these samples, for instance those from Mianus River, Conn., .and
Princ.ess Bay, N. Y. On the other hand, such .areas as Oyster Bay.
Hempstead Bay, and Great South Bay are far from any known
llAOTERIO~GY
AND OHEMI STRY OF OYSTERS
&O!lrce of metallic c.ontam;.n,ati9n, ;md Wacha preagu e, Va., is ..far
from any manuf acturin g.cent er. Yet .oysters from these waters
shQW the presepce of heavy metals . There is reason to believe
.that
oysters will absorb from the water, almost any substance which
it
contains. Thus, oysters taken from the vicinit y of dye works where
quantit ies of aniline dyes were being discha rged had. distrib uted
throug h theil' meat a variety of ,aniline colors.
Chemi cal analysis shows that oystcr meat c~mtainselements
make it a valuable food. The Lancet (1) reporte d that oysterswhich
coD,­
tain all classes of nutriti ve materi al in readily assimilable form.
The Ollice of Experi ment Station s, Depart ment of Agricu lture,
stated that there are.23.5 .calories in 1 pound of oysters (3).
.'
From its high conten t of soluble protein s and its high minera
snIt conten t there is every reason to believe that the oyster is a highlyl
valuab le !lddition to the diet. One gallon of good-g radeoy stel's,
if
not cxcessi':ely washed, weighs about 8 pounds and 11 ounces
.
This
will furnish Itbout 1.75 pounds of dry solids, a large propor tion
of
which is protein and valuab le minera l matter . Mitchell states.
that
the plltce of oysters in the dietary is not just the same as that
of
meat or fish, .but is more like that of ac.erea l or vegetnble. Labora
tory experim ents have shown that as much as 40 per cent of the solid­
matter in gl~ound oyster meats is soluble in water. These
soluble solids include portion s of all the valuab le food constiwater­
·
of the oyster, both organi c and minera l. Calcium, phosph orus,tuents
and iodine nre also presen t in oyst.ers in apprec iable quantit ies.iron,
The pl'\'lsence of VItamins, or growth -access ory elements, in oysters
has been reporte d by several investi gators. Rando in (73) reporte
d
the results of such a study in 1923, and D. B. Jones, of the
of Chemi stry .Rnd Soils, three years later publish ed a paper.Bureau
on the
value of oysters from the standp oint of nutriti on (52).
Even though a pound of oysters is nearly four-fi fths water there
is no waste of bone, cartila ge, or other inedibl e part, as in meat.
Oyster s produc ed under proper sanitar y conditions and not soaked
exc.essively during ~yashing and subsequent handli ng are wholesome
and nutritio us.
SHELLS
The results of analyses -of oyster shells made by· the Bureau of
Chemi stry are ghTen in Table 6.
TABLE
8,_·
.&~.
G.-Com p08ition of oyster 8hell8
ConstltuenLs
I--~--~-.--~--~-.---.--~~
~-~---.~-.--.--.~~
AI
Ca
Cu
Fe
Mg
MnP,O ' BIO,' Zn
~~~ ~Bi
'CI
Ico.
FI' N
.u·
terl
.I'
.
- - f - - - - - - - .---- ----- ' ------~-, - - ,- - - -
­
P.et.P.c/ . P.et. P.et. P.et.P.e t. P.d. P.d. P.d. P.C1.
P ..d.P.d .. P.d;P.et .P.d;P.d .
I ••••••• o. IM5 38. 7B-.....
0.183 O. 00\l 0.075 0. 570 ...... L 41
0.27 O. 0034 '57.19.••. . 0.1116 ••'.'
2•••_.._ .04338. 81 O. 0025 0.11
.09 .189 .000 .073 .680 O.
0009 1.61
.28.0035 _.___ _____ .1116 ____ _
I
Loss above 110° O. Ignited.
, Loss ,to 110° O.
• A veraae for samples 1·.nd 2.
,
Nitrogen is actually reported twice, once as the element and again
as part of the organic matter. Disregarding its value as given in
Table 6, 98.72 per cent of the sample is accounted for. The other
1.28 per cent may be accounted for as sodium, oxygen, and sulphates,
traces of which are present in the shells.
As oyster shells are composed mainly of calcium carbonate (about
97 per cent), their principal use has been as a source of lime. This
rather high grade of lime is used in agriculture as a soil improver,
as a dryer for fertilizers, and for all other technical purposes for
which hme is ordinarily employed. The crushed shell sometimes goes
into poultry feed. Locally, the sheUs are sometimes used for road
buildmg. The most important use for oyster shells, however, is for
cultch, to which the oyster spat may attach itsel£ when" setting."
PHYSICAL AND CHEMICAL EXAMINATION OF OYSTERS
From the standpoint of regulatory control, physical and chemical
examinations of oysters are important. For instance, if the oysters
are bloated, almost white and bleached, with soft spongy texture and
little flavor and with the meats almost devoid of sahne taste, and if,on
draining, they show much thin watery liquor, they ar,e unquestion­
ably adulterated with excessive quantities of water. This may have
• been added thl'ou~h soaking or floating in fresh water before or after
shucking, througll improper draining after washing, or, less often,
through deliberate addition of water to the cans at the time of
packing. The conclusion that such oysters are adulterated is further
confirmed if, on examination at the laboratory, the percentage of free
liquor which can be drained off is greatly in excess of 5 per cent by
weight. Further, if the solids and salt contents of the meats and
liquor are low, adulteration with excessive quantities of water is
proved.
Thus the most important determinations in detecting watering of
oysters are the physical examination and the determination of the
quantity of free liquor, together with the.determination of total solids
and salt of the meats and liquor.
In making a physical examination of oysters, size, color, texture,
flavor, and sali~lty (by taste) of the meats are noted. The quantity
and character of the liquid present, with special note of its color, con­
sistency. and taste are recorded.
The following determinations are almost always made when con­
ducting chemical examinations of shucked oysters: Net volume
of the contents of the can, quantity of free liquor removed by drain­
ing, percentage of meat, percentage of liquor, solids content of the
meat, solids content of the liquor, chloridi:lS in the meat, and chlorides
in the liquor. The following determinations are occasionally made:
Ash of the meat, ash of the liquor, protein, ether extract (fat),
acidity of the liquor, and heavy metals. The following determina­
tions are rarely made: ReduciIig sugars, glycogen, and composition
of the ash.
Net volume of can \meat'lnd liquor) .-During shipment or storage
oysters tend to pack mto a ilolid mass and so occupy less spa.ce than
when fil'stpacked for shipmeut. In order to 10Qsen the mass, so
tha!; it will occupy its original volume, the oysters are poured back
and forth into the standard measure before the final volume is noted.
,
BACTERIOLOGY AND OHEMISTRY
OFOYS~ERS
This "fluffing" process brings them back to approximately their
original volume.
F1'ee liqU01' content.-The free liquor content is of very great im­
portancens indicating probable adulteration with water. Where
labora~ory facilities are to be had, the determination is made with
~reat precision, the results being reported as per cent by weight, by
the following procedure:
Empty the contents of the can (if 1 gallon or larger) into a
suitable receptacle, which will admit of thorough mixing. Weigh ac­
curately on It torsion balance (accurate to G.1 ounce) into a counter;-.
poised pan about 1 quart (approximately 214 pounds) of the mixed
sample. Throw this weighed sample on to a colander (preferably flat­
bottomed) and drain for two minutes, receiving the liquor iI). a
counterpoised pun. Weigh the liquor und calculate its percentage by
weight. This sample can be reserved for chemical analysis.
When it is necessary to make this determination in the field, where
facilities do not ulways permit accurate weight determinations,'
report percentuges by volume of liquor drained off, using 1 gallon
of the sample. If a standard. gallon pot with vertical sides is avail­
able, this can be done conveniently by measuring the depth to the
material. From this calculate the percentage of volume of liquor
drained off. This gives approximate results only.
Obtaining and pl'epanng samples to'l' .clunnical analysis.-To
obtain a representati\re sample, a quart (never less than 11 piI)t)
of .oysters is used. The portion used for the determina~ion of free.
liquor is suitable. If the free liquor content has been found t.o be.
less thun 5 per cent, the liquor may be reinixed with the oysters and·
the whole sample analyzed. If more than 5 per cent of liquor is
present, it is best to analyze the meat and liquor separately and to
calculate the results to the basis of the entire 'Sample.
Grind the meat in a food chopper, passing it throlJgh the ,mill
twice, thoroughly mixing between each grinding. Preserve the
ground sumple in a tightly closed jar on ice until the examination is
completed. Portions for analysis should be weighed at once. Whim
the liquor is to be analyzed a clear solution can be .obtained by plac­
ing the liquor in a tail benker in the refrigerator. (Owin~ t.o its
thick, viscous character, filtration is practically impossible.) A
scum SOQn rises. This can be removed with a bent spatula and the
olear liquor can be poured off from heavy shell partIcles and other
materials which settle to the bottom, It is then ready for analysis.
'J'otal 80Uds.-Duplicate determinations should always be made.
Weigh accurately 10 grams of the ground sample or of the clarified
liquQr into a flat-bott.om platinum or nickel dish, 3 to 3% inches
in diameter. Spread the sample evenly over the bottom of the dis4,
using a little water if necessary to &,et an even distributiQn. Evap'­
orate to dryness on a steam bath llnd dry at the temperature of boIl­
ing wuter to c.onstant weight. Avoid long henting. Oyster solids
easily char, and heating shQuld be discontinued before this point ,is
reached. Express results as percentage of SQUds on the meat and
liquor.
.
.'
..
Ash.-H a platinum dish has been used for the determination of
the solids, this may be used for the determination of the ash.. Other­
wise, weigh .out a fresh sample in either platinum or porcelain. Ash
.
1-21
TECHNIOAL BULLETIN'
64J,
U~ S. DEPT'; OF :AGRICULTURE
the' inat~rial at a-low' temperature in 'a muffie. "Tlie teinperattitl~
should be kept below dull redness, as part of the ash may' be lost ,by.·
volatilization at higher'temperatures.. Oyster sOlids burn readily to
a ,gray ash, free from carbon, 'if the'temperatui'e is not allowed,to'
ris~ to !,i point where any' fusion which occludes carbon particles'
takes pl~ee. Weigh. the ash an~ reJ?ort perce~tage:by weight.
'
OhZ01-i.des.-ChlorIt:'es are ordmanly determmed m both the oystel'
liquo'jo" and the Ineut after' incineration.' Direct ashing results 'in
loss Jf dilorine. This may:be prevented by the addition of asu.b'­
stance which will insure an alkaline ash. Sodium carbonate' has
been employed, but, on a~count of its fusibil~ty, it is not entirelysuit~;
able; CalclUm acetate IS to be preferred.
.
. ", .
. :L\Iix 10 grams of the sample~n a' plath:~um. dish with 10 cubic 1
centimeters of a 10 per 'cent solutIOn of calclUm acetate and evapor~
ate th~ mi~t'ure to dryness. Then 'ash,' preferably in a ml!ffie'lit 'Ii
tempei'ature not exceeding; dull redness. Take up the resulting
gray'asli iriwater 'acidified with'dilute nitric acid,(-l +4). ChlOrides
ate lietermined according to the official volumetric method (7).
Protein.-'-Using2 grams of ,the sample, determine total'organi~
aiid(tmmoniilcal nit,rogen accor4in~ to the Kjeldahl or qunning
method ('7); 'rhe mtrogen muHaphed by the factol"' 6.25 gIVes the
protein.
.
. .
'
.
,.
Ether erntmot.:-'-Dry 10 grams of the material and transfer to a
sui~!lble continuous extractor. Extract for, 12 hours with absolute'
ether. ' 'Regrind the sample; and continue the, extra~tion for 'four:
hOllts longer. Evaporate the ethel', dry the ether extract, ltnd w~igh.
Report as percentage of ether ~xtract. ' .' .
"
. 'Gl'!Joogen and.mgar.-Inroutme exammatlOns of oysters for'regu­
latorypurposes, glycogen and 'sugar hllve ,not gerlerally been- deter­
mined. Mjtchell (6~) "and Dill'(3J) made many determinations of
sugar and glycogen in shellfi'sh. The'following method, used by Dill
on' Clams, isrecomm'ertded:'
., ' '
,
"
Extjact' 2.5. grams of the grounc;l sample· with 85 per cent alcohoL"
Heat to bOIhngand decant through a folded paper. ~ Thenreex~'
tr,act with th'ree portions of 100: cubic centimeters .eachof 65 pel< cent'
alcohol,' heating every ti!lle .. ~vaporlite the combined filtrates'toa
volume of about' 400 CUbIC centimeters. Then 'follow the method of
th~, Asfjociationi of Offici!J,i Agricultural,Chemists' (7).
' ;,
, 'Jloidity of li11uor.-Titrate 25 cubic centimeters of clarifie~: liquor
with O.Fnorinal al~l!-li: using phenolphthalein I;lS an indicatorj'Ex~1
press'results RScuOic centimeters of 0.1 normal alkali per 100 'cubic
" ~, .,,·r;
centimeters' of' liquor. .
; ",
',!!f3avp. ~ta~8i-Col?p~r, l~ad, zinc, and arse~ic are rarely deter~:
mmea, m routme regulatory work. The officml methods (7) fol"
deteri:;lining metals in fdbd hav~ been succ~ssful, 20' to 50 grams of,
gtound sample being used, aqd the organic matter being destroyed,as'
',' '
,
.'
outlined.
. Oompos#ion 'Of ask.:-Thecomposition of ash is'rarely determined.
Tlie official methods for plants (7);'however, are applIcable fot th~\
determination of th~ ord~n!lry constjtueqts of the ash of oysters.
.'
From-'the" regulatory standpoint; mere chemical examination of !l
~\l:Ii}ple. of. ?y~ters ~eans little 'unl.ess something abouu the locality ip..
WhICh It orIgmated ISlmOwrr. It IS necessary to compare the analYSIS
BACTEUIOLOGY: AND CHEMISTRY:. OF OYSTEI:S
13
of the unknown sample with that of an authentic sample from the
same locality prepared under good, commercial practices., FoX" in­
stance, it would be useless to compare the results of an analysis o£ a
sample of oysters from the brackish water of Chesapeake Bay, the
solids content of ,vhich, after washing, is generally between 12 and
16 per cent., with the l:esults of an analysis of oysters from New,
England watei's, where the solids content is generally neal' 20 per
emit, and then attempt to draw conelusions regarding adulteration
with water. On the other hand, if a type saIilple is available for
analysis and comparison, it is easy to state whet.her or not the given
sample is adulterated with water.
If no lmowledge of the oystersj origin is available, it. is hest to
rely upon an objective examination by one who is familiar with oys­
ters, supported by such info'rmation as may be obt,ained from the,
simple determinations of frce liquor content and solids and salt on
the meat, the liquor, and the ent.ire sample.
Spoilage in oysters generally takes the form of souring. Even:
b.efore there is any pronounced, odgr of putrefaction there is a pro.­
nounce.d develo~J!ient of l~ctic acid,in th~ liCluor ~n? in. the meat.
For tIns reason, If the qlicstlOn of spoIlage IS raIsed, It IS best to deter­
mine acidity of the liquor. In the fresh oysters this is equivalent to;
only 1 01' 2 cubic centimetel'S of 0.1 ~JOl'malalk~li per 100 cubic
centimeters, but. it rapidly increases .as spoilage sets in.
Most oysters which ente.r interstatecornmerce are transported 'in
nonreturnable friction-top cans.. The gallon size is the one most
commonly used, altbough other sizes, both larger, and smaller, ~rom
1 pint up to 10 gallons are also employed. Competition brought into
se.rvice the so-called "neat," can. When commercially full this can,
generally holds from 1 to 4 per cent less than its supposed capacity.
The difference in size between such cans and cans of the proper size
is not noticenble to the casual observer. To. control effectively the
use of such containers and to prevent any violation of. the net weight
amendm~nt to the Federal food and drugs act, a careful determina-·
tion of the .net contents of the can must always be made when a. sh~pment of oysters is inspected.
.•
The canning of oysters received attention from the Bureau of,
Chemistry. Cans of each size must contain It specified weight of
oyster meats, and the net weight of each package must be conspicq­
ously marked upon the label. Efforts have also been made to put an
end 'to the practice of using for canning sour or decomp03ed oysters
that have, become unfit for the fresh-oyster market. Slack filling an~.
using decomposed oyste.rs for canning have been largely corrected by
lee:alactionand by educational campaigns.
;.
OYSTERS AS CARRIERS OF INFECTION'
For over a century oysters have been regarded with suspicion as
potential and, sometilnes' actual c!1l'l:iers of disease-producing bacteria,
especially those ~hat. cause ~yphOId fever, ,dysentery, cholera, and,
other gastroenterIc dIsorders.
The brackish waters of bays and streams, where oysters find the
best conditions for growth and reproduction, have often been grossly'
polluted with S'ewagc and trade wastes from large cities and indus-.
trial centers. At one time it was common prr.ctice to hold oysters in
•
Vi
TECHNIOAL BULLETIN 64; U. S. DEPT. OJ!' AGRICULTURE
storage pits !md .floats near the shucking houses, to allow. them to
" drink' in water less saline than that in which they had grown',
in order to " flttten " them or give them a plump appearance, and to
store surplus stocks of shell oysters until they were needed for shuck­
ing.. Many cases of typhoid fever and gastroenteritis, in ;both the
United States and Europe, have been Rttributed tv the eating· of
oysters thus floated or stored in polluted water. Sometimes the
epidemiological evidence seemed to establish beyond doubt that the
oysters were the carriers of the infection. 'l'hisconclusion was
reached in spite of the fact that in almost every case it was impossible
to isolate the specific organism of typhoid fever from oysters of the
same locality. In other cases the epidemiological evidence has
strongly indicated that oysters ~aused t~le trouble. The data, how­
eYer,.<hd not prove the case agamst the oysters beyond a rellsonable
douot. It is not within the 'scope of this bulletin to discuss in detail
the epidemics of typho.id feyer alleged, and sometimes proved, .to-have
been caused by the consumption of raw oysters. This is fully covered
in'the literature (~, 8, 14, 17, 18, fJO, f313, ~5, f39, 313, 41, 59, 60, 61,
64,66,68,88,85).
Very soon after the 'passage of the F6cleml food and drugs act in
1906 the combined efforts of Federal, State, and municipal' agencies,
with assistance from the industry, were directed toward correcting
insanitary condi~ions i~ the. :l?reparation of oyste~';S f?r· the. market.
After a short..pe~·lOd of rndeclslOn and unrest, practICes III the mdustry
w~re revolutlOillzed to_ the extent that oysters "Voere no longer per­
mItted to !be marketed from; or to be floated ill, polluted water.
Consequently, from 1916 to 1924 there were no reports of illness
from infected oysters. The ou'tbreak of a large number of .typhoid­
fever cuses in Chicago, Ill., New York, N. Y., 'Vu;shington, D. C.,
and 10 other cities ill the eastern part of the United States during
the winter of IV24:-25 again :focu,sed attention upon oysters as pos­
sible carriers of disease-producing bacteria. The ·investigations by
Lumsden and hi;sassociates (60), by Btmdesen (13:3), 'anclby Hards
(41) indicated that oysters were the carriers of the typhoid~fever
organism. Although the evidence against the oysters was purely
epidemiological, it was so conclusive that the case appeared to be
complete: The actual source of contamination could not ,be deter­
mined. The investigations and conferences following therep.ort of
this epidemic disclosed certain practices in producing and marketing
whieh still needed improvement. At a meeting of oystermen and
health officials at 'Vnshington, D. C., in 1925, resolutions to correct
these' conditions (60) were adopted.
Although typhoid feyer is the disease most often discussed .in
this connection. such <liseases as cholera, diarrhoea, and gn;stroenter­
itis also may be transmitted by shellfish (19, 934). Two cases of
illness ascribed to the eating of oyster,s, rep.orted by Casey (134) and
Brosch (19), are interesting in thi:,; connection. The symptoms werc
entirely ~liffer.ent from those of t;yphoid fever; they resembled those
of botulIsm, III that the central nervous system was affected and
death was due to ,suffocation. In each of these cases the victim was
aware that the oysters were bad as soon as he h~d eeten them.
Botulism from shellfish is of very r.are occurrence.
BACTERIOLOGY AND CHEMISTRY OF iOXSTERS
Obviously oysters that have been grown or fiol1ted in polluted
watm' or that have become contalninatecl with filth during handling
are lmdesirable as articles of food, regardless of whethet· or not
they contain specific organisms of disease. The Federal food and
drugs act (01) prohibits the shipment in interstate commerce of
articles of food which are adulterated. Among other definitions of
adulteration (91, sec. 7) is the one which states that a food is
adultemted jf it consists in whole or in part of a filthy, deccmposed,
or putrid animal or vegetablo substnnce. It has been claimed by the
Federal officials that oysters containing excessive numbers of Bacillus
cold are adulterated within the meaning of the food and drugs act,
and this position has been maintained through trial in court.
BACTERIOLOGICAL EXAMINATION OF OYSTERS
STANDARD METHOD
The collection of epidemiological evidence by European investiga­
tors, who were the first to study the relation of polluted shellfish to
disease, was SOOD followed by attempts either to isolate the specific
organisms of typhoid fever and cholera or to obtain bactel'iolooical
data to substantlU,te the claims that oysters grown in certain locafities
wcre polluted with sewage and were therefore potential sources of
danger to health. The technic and culture media, used by the early
inycstigators (21,42, ¥J, 51) varied with the individual making the
eXlunina.tion and wi th the investigation.
In the United States early workers on the bllcteriology of ;the
oyster also adopted methods and media varying with the individual
and the ploblem (16, ~7, 36, 17, 75, 7'1, 8~).
Up to and even beyond the time when a standard method of bac­
teriological examination was proposed, Eome investigators advocat~d
the use of the shell liquor only, some preferred the crushed meats
alone,nlld others recommended that both the meats and the liquor
be used.
The eli versity of methods used in clifierent laboratories produced
confusing results that could be neither compared nor intelligently
used for Imy well-regulated plan of sanitary control. The pressing
need wus for a stlmclal'd method for the bacteriological examination
of shellfish sponsored ancl approved by some ol'ganization~ such as
the AmeL'icnn Public Health Association, which also devises and
apprOVeS standard methods for the examination of water and milk.
Renliz.i~,!r this neec~ H. D: Pease,s then of the Lederle ~aborat()l'iesJ
New Yorl\., N. Y., G. u. Whipple, of New York, and S. DvM. Gage, 01
the Massachusetts State Board of Health, held several conferences
during 1909. As It result of these conferences~ at the 1909 meeting
of the American Public Health Association It committee was ap­
pointeel to develop a satisfactory method for the bacteriological
examination of oysters and other shellfish. The following year this
committee suggestecl a method for the determination of total counts
of bacteria and the presence of Badllus coli and what is now accepted
• The Information regarding the cvents Inllncdint!!ly Icndlng to the nppolntll1fmt of the
Stnmitll'(l l\Iethod~ COlllinlttc~ und thc curly history ot the activlticR of this committee were
vcry kindly HIIlljlli(!d by H. D. Pen Me. dlr(!ctol' of the Pcnse Lnhorlltorlcs, New YOI'k, who
WUH secl'l'tnry of thc originnl commlttec.
18sthe stlUldard method of scodng oysters based upon the prevalence
'of Bacillu.8,(JoZi (3). In 1911 this committee modified somewhat. the
original procedure and considered the hibernat.ion of oys.ters (4).
In 1919,the p.rocedure for the bacteriological examination of .oysters
and other shellfish now followed was approved by the American
,Public Health Association (5).
BACILLUS COLl
At various times in the development of the standard methods .and
the application of the results obtained it has been suggested that
BacillUs coU scores of 23 and 32 are indicative of pollution. As fur­
ther investigations have been conducted and more information has
been obtained l:egarding the significance of this score it has become
generally established among Federal, State, and mlmicipal author­
Ities that a B. coU score in excess of 50, in either shell or shucked
stock, indicates excessive pollution. Any conclusion regarding the
sanitary quality of the oysters based upon the bacteriological ex­
aminatIOn, however, shall be supported by data from a sanitary sur­
vey of the locality whel'e the oysters were produced. Data obtained
from a bacteriological examination can be interpreted properly only
when something of the source of the oysters and the conditions under
which they VTere hancllecl is known.
SPECIFIC ORGANISMS
The is.olation from oysters of the organism causing typhoid fever
and the bacteria that are the specific CRuses of other diseuses iS1im­
practicable. Attempts to isolate the typhoid bncillus and the cholera
vibrio from oysh~':'3 from polluted sources have met with but little
success. Klein (181) was able to isolate from oysters an organism that
culturally and serologically answered all the tests of Bacillu8 typlw8U8.
From his description of the organism thel'e is no doubt that he
actually obtained the typhoid-fever bacillus. Fuller (36) eites an
instnnce in which the isolation of B. typh08U8 from .oysters was
reported at a meeting of physicians at Constantinople. Johnstone (51)
states that on oneoccllsionhe was able to isolate from mussels an
organism which be considered to be B. typhOffUS. Fl"om his de­
scription .of the isolnted organism there is some doubt as to its proper
identification. Finally, Stiles (83) isolated from oysters 1l0ated at
Inwood, N. Y., an organism that was identical culturally with B.
t?/ph081/,8 and that was agglutinated in a 1 to 1,000 dilution oy typhoid
serum. Stiles was able to isolatc this organism 21 dnys after the
oysters had been removed from water. These four instances are the
only ones .recorded in the litel"lttul'e where investigators have been
able to isolate B. typlwsU8 from shellfish infected under natural
conditions.
Less success has been met in attempting to isolate the cholern vibrio
from shellfish. IGein (181), among many others, made repeated at­
tempts to isolate this. organism, but without success.
It is not difficult to understand w:hy it is pmctically impossible to
isolate specific orga:>;isms
disease, even with the most recently i~­
proved methods of lS()'!~tIonandculture. The numbers 'of typhold
bacilli being dischnrged in sewage are not consb,mt and by the time
.of
r .
. il,
,
BAOTE!tIOLOGY AND CHE:M:If:i~rRY
OF
OYST£RS
i1
the sewage reache!; the oyster beds the dilution ha.sbecome so :grellt
that !lIly ,bllcilli present in the eHiuent have become widely distribQt~d.
It lS .likely IUSO thut mnny of them have succumbed to unfa:v.orable
environment. It is not probable that ,each oyster on .a 'bed willl'eceive
the same number of typhoid bacilli, so that the chance of finding the
organisms in the examination of comparatively few oysters from a
polluted bed is small. Nuturlllly, it is not practicable in routine
work to e..'i:umine bacteriologically enormous numbers of oysters from
Ilny one beel in an attempt to reduce t.his hazard of sampling. Wher,e
oysters from n particular locnlity huve been suspected as the cnUSe
of typhoid feyer the epidemiologicul evid~nce, owing to the incuba­
tion period of the disease, has been obtu ined two weeks Q1' more after
t.he infection. This further l'emoves the possibility o£ finding the
<:uusative orgnnism in oysters from the suspected region. What is
true of B. typlw8!t8 in this resped is equaUy true of the other patho­
genic b:1.cter.iu thnt might be pl'{~sent in sewage.
Becamle of this practical impossibility of isolating specific Ol'gnn­
isms of diseuse from oyster's, the exumination of shellfish for sanitary
quality nnel for potentiality ns acnrrier of infection has depended
upon tests fOl' the presence of B. coN, which is the common and con­
f'tant inhnbitnnt of the intestinnl tract ,of mnn and other warm­
blooded' animals. This organism is constantly present in sewage and
can he ensily isolll.tec1 und identified in routine wOl;k by the use of
simple cnUm'al tests as outlined in the standard methods for ,the
bacteriological examination of either shellfish or water.
BTREl'TOCOCCI AND ANAEROBES
Although but little significance is now Itttached to the presence in
oysters of'streptococci anel sporulating anaerobic bactel'ia, numerous
uttempts hnve been made in the past to correlate their -presence in
shellfish with sewag'e pollution. Streptococci are not readily grown
on the culture media used in routine bactet'iological wnrk. '1Jhe
presence of these organisms in large numbers may be indicative of
pollution, but the difliclIlty of determining the significant types of
stl'eptococd and the 1Illlubers pn~sent have led bactedologists to
abandon them us reliable indices (If sewage contamination.
.
'Vhen many samples of oysters IU'e eXltmin~~ by the stand~rd
method it frequently happens thut large quantities of gas Ilre pro­
duced in lactose broth und give presumptive tests for Bacillu8 coli
which CILn not be confirmed by streaking on Endo medium. T.he
Qrgnnisms producing this gus will not grow on the surface ,of solid
media and, no doubt, belDIlg to the lurge group of ll.naerobicbacteria,
such liS B. 10elcldi und B. 8pol'ogene8, which have been frequentl:v
isolated from water and soil. Most of these organisms nre sp'ore
formers und are resistant to the unfavomble conditions that they
encounter in llUture. Their presence in shellfish lacks the signifi­
cance attacbed to the presence of B. coli. It bas not been proved
that they are of intestinal origin only. Furthermore, in tbe dorrn:mt
spore stage these orgllllisms may exist for long periods in water wid.
their vitality lIniml)llired, and thus be obtained from shellfish grow­
ing on areaS so remote from the source of pollution that all danger
from nOllsporulating forms like B. f:1fplw8U8 is removed. In his
780[,5°-28--2
'j
J8
TECHNICAL BULLETIN 64, U. S. DEPT. OF AGRICULTURE
investigation of the Potoma<.: River, Cumming (30) found that the
numbers of spores of these lactose-fermenting anaerobes werc remnl'l(­
ably constnnt in the river water. The spores were often found in
the best river water in 10 cubic centimeters. Their number does not
indica.te the degree of pollution, as does the number of B. coli. These
spores are n1so often resistant to treatment with hypochlorite. Even
waters so treatEld wiU contain viable spores. Several investigators
have shown that these anaerobes are commonly found in sources
remote from pollution with intesti.nal contents. Although it is
true that they occur and multiply in the intestines of warm-blooded
animnls, their presence in shellfish can not be Ilcceptec1 as n reliable
index of sewage pollution. If the examiner depends entirely upon
the presumptive test for B. coU (gas production in lactose broth) he
is likely to be in error, owing to the presence of these lactose-fer­
menting anaerobes. However, false presumptive tests are readily
excluded from consideration by the failure of the anaerobes to grow
aerobically on Endo plates.
POLLUTION OF OYSTER BEDS
BACTERIAL FLORA OF UNPOLLUTED OYSTERS
~
In order to detect the presence of sewage and filth in oysters by
bacteriological methods it is first necessary to know the bacterinl
flom of the normal, unpolluted oyster. 'rhe presenc,e of Bacillll,s
coli cnn not be used .as an index of pollution until it has been defi­
nitely shown that oysters do not contain B. coU when tnken from
cleun undo unpolluted water.
Many investigators 11nve reported thnt their results show con­
vincingly that B(JC'illJ!ts coli is 1l0t an inhabitant of normal, ·unpolluted
oysters (~1 '!J7, 35, 36, 43, 46). In the course of routine work con­
ducted in tIle Bureau of Chemistry a very large number of samples
of oysters were examined by the standard method to determine the
presence of B. coli. In many oysters obtained from sources free
from pollution no B. coli or other lactose-fcl'lnenting bacteria were
isolated. Investigations have established the fact that the normal,
unpolluted oyster does nnt cont/Lin B. col-i. The standard methods
for the bncteriological examination of she11fish wP,re devised with
this filet in mind. Hunter und Linden (..i9) identified the ol'gltnisms
isolated from decomposing oysters and confirmed the findmgs ·of
previons invl'stigatol's (:94, 36, 79, 106) that the bacterial flora of the
oyster was composed of common water and soil organisms, including
cocci, nonspol'e-forming, Gram-negative aerobic bacilli, spore-form~
ing, GrlUn-positive aerobic and anaerobic bacilli, lactobacilli, strep­
tococci, and yeasts.
'BACTERIAL FLORA OF POLLUTED OYSTERS
Oysters from polluted sources contain, in addition to the bacterin
mentioned, organisms that are indicative of sewage pollution. O. A.
Fuller found in polluted oysters Baaillu..~ coli, B. cloaca.e, B. welchii,
and B. aerogenes, none of wh:ehwas found in oystel's fmm un­
polluted sources. There is still some doubt regarding the vaillt!
of B. ClOlUJM, B. 'loeZcldi, B. aeJ'ogenes, and other such organ­
BAOTERIOLOGY AN,D OHEMISTRY OF OYSTERS
19
iSl}lS liS indices of sewage pollution, as their origin has not been
satisfactorily deter~ined. It is frequently stated that these /Jacteria
are cOlllmonly obtamed from the soil and from other sources not ~en­
erully considered .as polluted. On the other hand, these orgl!Dlsms
occur also in the intestines of warm-blooded animals and therefore
aronse suspic-ion when found in oysters and water.
'
In establishing a bacteriological standard for drinking water to ibe
used on common carriers in interstate traffic, the advisory committe~
appointed by the Surgeon General of the United States Public Health
Service determined in what llllmbers organisms of the Baoilluscoli
gl'OUP might be present before the water W!lS considered unfit for use
(99). lfor the purposes of the standard established the B. coli
group was defined as in the standard method for water analysis issued
by the American Public Henlth Assoc.iutjon in 1923 ((], p. 100) "as
including allnonspore-forming bacilli which ferment lactose with gas
formation und grow nCL'Obically 011 standurd solid media. "This,
definition of the B. coli group, which does not differentiate between
the yarious forms or types of that group, would include such
organisms as B. ae'I'oqenes and B. cloacae. vVhether snch a ruling
clln be al)pliedsafe1y to shellfish .is un open question, but the
presence of these organisms in excessiye numbers in oysters should
call for a careful survey of the territory surrollllding .the oyster beds,
with a view to determining their possibl~ source and, therefore, ;their
significllnce in judging the sanitary quality of the oysters.
VIABILITY OF BACiLLUS TYPHOSUS AND B. COLI IN OYSTERS AND WATER
Innttcmptillg to' use the presence of Bacillus coU in oysters as an
index of recent pollution, with consequent danger to the ,pJlQlic
health, it is necessary to knO.w something O.f the longevity or viability
of this organism in oysters !lnel in sea water. If B. coli can sur­
vive for only short periO.ds uncleI' the conditions met outside the
bodies of warm-bloO.ded tUlimals, the use of its presence as an indi­
Clttor of pollution is greatly restricted. Under snch conditions water
and oysters mil?ht be gl'ossly polluted with sewage und yet not show
positive tests for the presence of B. coli. On the other hand, if
B. coli will multiply 0.1' survive in natural waters or oysters for
extremely long perJOds of time, it is possible thnt their presence can
be dctectecl long after all danger from the pollution has ceased~
B. coU suryi viIlg for long periods in sea water might reach.
O.ysters on beels remO.te from the source O.f the pollution. Further~
more, in O.rder to' knO.w whether Dr not the. presence of B. coU
in oysters or water remote from the source of pollution indicates that
the shellfish is still potentially dungerous to' health some information
must be had regarding the IO.ngevity of B. tYPM8U8 in oysters as
compal'ed with the longevity of the colon bacillus. The cc:>llectiO.n of
such information has called for investigations to determine the length
of time B. ty phO$'ll8 and B. coli can surviye in sea w.ater and .in
oysters floated in infected water.
Another phase of this prO.blem of equal importance is the longevity
cr viability O.f Bacillus typhos,ltsanci B. coli in shell and shucked
oysters removed frO.m the 'Water and stored at various temperatures.
It is extremely impO.rtant to' know whether oysters naturally in-.
fected with B. typ/wsus OIl the O.yster beds offer such an unSUItable
20\
TECHNIOALBULLETIN64, U.S.DEPT. ,OF AGRICULTURE
habitat 'for this organism that it can not multiply but quickly,
,perishes, thus making the infected 'oysters safe for consumption soon
a.fter their ,removal fmm the polluted grounds. ,In studyingepi­
demicsof typhoid fev:er alleged to be due to oysters it is helpful to
kIiow' 'whether or not B. typlw8u8can survive in stored shellfish long
enough to cause the illness.
'. With respect to the 10ngevityof Bacillus coli in stored oysters, tthe
tiseof its pt'esenceas the criterion of judgment upon which the pres­
en~standa:rd method of ba.cteriologicalexamination is based will fail
entirely if tlle' colon bacilli either multiply rapidly or perish ina
shortthne within the ,oyster. If oysters ihavinga B. coU score of
less than ,50 shortly after ,removal fi'om the water develop 'a score of
500 or more during storage :in the shell at low temperatures ordur­
ing shipment from ·the Atlantic coast to the Middle West, then ,the
bacteriological ,examination at destination according to the standard
method l<;>ses :its vilclu~.. Suchoyster!:l should not be held, as grossly
pbllutecl If such conclttlOns are true.
'
,,
, 'In view of these considerations much experimental work has been
.done by bacteriologists interested in the pollution of shellfish to
determIne the longevity of Bacilhl8 typlw8u8 and B. coli in oysters
aIidsea water. In fact, investigations along this line were among
the 'first studies 'made on the bacteriology of the oyster. In 1889,.
de Giaxa publish(~d the results of his investigations of the viability
of B. tJlpIWL~.s in sea water (39). A paper by Krum\viede, Park,
and others on the longevity of this organism in oysters appeared
dtiHng1926 (58). 'The results of the outstanding investigations ·of
tb,isproble.\ll .are summarized in Table 7.
.
,
'
TABr.!: 7.-Sil1nmU'l'11 of investiga tio II & reJlortcd. in tltc litem/tire on the viabilUy
'. .
of'Qacil/u8 'tllph081l8 (/.]I(J. Baeillu8 coli in01l8ter.~ am! water
Villblllty 01 ilacillus typllOsUIJ
inlnvestigato: '
Viability of Bacil
coli in­
Z".
DnW
Oysters
Unslerl· Sterilized
~!~~~ir
wo ter
Water
Oyster'
-'------------1·-- --- ------ -----de ,Giax8\1J9) • ________________ • _____________ _
1gein (Bl) __________ ________________________
Foote ($4)---------------------------------__
~
i:~b~~{l~:::::::::::=:::::::=:::::::::::
~~a~t4~64i::::::::i:::::::::::::::::::::::::
~lrr:!iAt~~::::::::::::::::::::::::::::::::
St.,lles
(83) __ .,.•• ____________________________ _
188\J
180.1
1895
1800
11l!}1
11104
!!lOI
HI()!
1II(f!
1110i;
1912
Dav.,
, 18
'ao
Days\)
21
18
60
DaV825 __._c
Days
Dav_ _
_______________
________ . ____________________ •
______.--- ___ c_______________ _
_____________________________ _
_____________ . ____ ._ ._________ __________
'0.28-42
:
:::::::::/
__________
]0
1
_::::::::: ::::::::::
5-,82~
___ ~!:~:5
10 3
______
. ______________________ _
-----i·-2i- :::::::::: :::::::::: ______ ~~ _______ ~_~~
',Italic nwnbcrs in parenthesis reler to "Liternture cited," p. 70
I Oysters ,IIQatiJd In tanks 01 Inlected water
•:Oystei'S'slorcd in tho shell.
'
•. " Ver:r.cold water used. In wanner water thero was a gradual decrense after one week.
not detected after threo weeks.
I Shell oysters stored In n "dry" condition.
• Shell oysters held In cold water.
B. 1II1!AO&w held In Chlca}!o 'Hlverwoter. whleb WI~q really dilute sewage. I' , B. lyphO&!l8 beld In colloidln Slicks suspended In Lllke Michigan water. • B. lyphO&u, held in celloidin sacks In the Chicago Drainage Canal.
,10 B.,tVphosu.. held In celloidin sucks In tho lllinois Hiver. , 11 .Sbell oysters hold out of water. 'Oystors were deud ut end 01 17 da~. • U Shell oyst~rs ,held ut 39° F.
,1
'7
___ •__________________________
B. IVphosus IVa.'
.• BACTERIOLOGY AND..CHEMISTRY OF :OYSTERS
T.AIJL!:
7.~S1Imtllary
.
'
21:
ofin:vestiga.fioo/l :reported in the Uterat1t'r,eon the"'ViabiZit,;.
and JJat;illu8 coli in oyster8 and tvater-Contl!lucd , •
,01 JJacillustyphostlS
• _I;t
Viability of Baci/lu. I"pho,"" ViabllIty· of Bridlhil
incoli 111-;_" •
Investlgalor
Date
Oysters
U nsteri- Sterilized
~~~~
watOr
'Wllter
- - - - . , . , - - , - - - - - - - - - - - i - - - - - - - - - - - - - .- . - --,-,1-',
Hound (16) ______________________ ••••••••••••
111]4
TonneY!lnd White (86) •.••• ____ • __ .________
192"
Jord!lll
__• _____• ___________••___.________
Kinyoun (56) _________ ._____________________
Krumwlede'!lnd :Park (581 _____.------------
1925
11125
lli2tl
(5~)
Da". __________
Dall" __________
Da,,"
__________
DaQ'
180
D,a,,~.
"100
:~~ \--------- ---------'- ---------- -----i~~-~·
"24 __________________________.--- __________.
15 ___________________________'____________ _
10
II
2J
49 ____________________________,________
~_~_
" 61
14-10
II.Shell oysters stored at.,1.5° C. (3-1.7° .F.)
Ii Shucked o)'sters stored at 98° F. " Shucked .oysters stored at 70° F_ II Shucked oysters slored at 45° F. 11 Shell oyslers stored ilL 70° F. 11 Shell oysters stored at 45° I". II Shell oyslers stored at 5° C. to 8° C.
(41° F. to 46.4 0 F.) .. Shell oysters stored on Ice !It 2.80 O. to 14.4° C. (37° F. to 57;9° F.)
." Shell oysters ilL relrigerator temperature. Oysters dead by lorty-first day. "'Shell oysters In water cold enough to Inhibit drinkIng. 2J Organisms on outside 01 shell. 8lU'vival varied with extent of contal!linatlon. ,
.~ Klein found that the cholera vibrio could be recovered from~ oy,s­
tel'S on the ninth day and fronl sea water on the fourteentll dllY:
after infection. Stiles (81) stated thatBacillu8 typ,lW8U8 will survive
in the soil for fit least 106 days. Vasquez-Colet (lOO) found that B~
typno8u8 might survive on fruits and other foods eaten .raw frollla
few minutes to three days after infection.
'
It seems to be well .established that Baaillus typh08U8 will exist
longer in sterilized sea water than in unsterillzed water. This is due
to the ·antagonism for the typhoid baciUusexerted by the other soU
aI;ld water organisms present in unsterilized sea ,water. It isalS<?
accepted that B. typlw81:i.S will live longer in clean water tb,an ,in
water containing a large proportion of organic lI~atter. This is
.illustrated by the work of Jordan, Russell, .and Zeit~(<54), who fo.und
tllllt B. typlw8U8 perished quickly in the dilute s~w:age of tbe Cw<:;ago
D,rainage Canal but survived in the water of Lake Michigan. '
view of the influence of such factors as the presence ,.of ,antagonistic
bacteria, the presence of organic matter, temperature, salinity, varia~
Gion in resistance of individual strains of B. typhos1Ul, and the num­
ber of bacilli used for tile. original infection, it is not ,surprising tha~
each investigation gives a different result. In fact, it is impossible
to draw.a general conclusion regarding the viability ·of these intestinal
organisms in water or oysters from any one set of .experiments. The
preponderance of the data indi~ates that B. typho~ will surviye
III water long enough to contammate oysters bathed III the sewage­
polluted water.
.
'. "
Fmthermore, Bacill!us tYPMSU8 will remain viable within ;the bodies
01' shell liquor of oysters long enough to cause illness when the'9Y~L;g
are eaten within the usual period elapsing between the time of re­
moyal from the infected water and the time of consumption. Many
of the factors considered in the discussion on the viability of the
rn:
"
22
TEOHNIOAL 'BULLETIN 64,
u.
S. DEPT. OFAGRIOULTURE
organism in water are significant in considering oysters. The tem­
perature of storage, the orginal degree of infectIOn, the condition of
the .oysters, and the -presence of antagonistic bacteria are important.
Many of theresuHs 1Il Table 7 are inconclusive in that the- typhoid
bacillus was isolated up to and on a certain date, when the experi­
ments were termillated and 110 furt.her efrort was made to repeat them
by prolonging the storage period. Therefore, many of the results
should actually be stated as " at least~' so many days or hours. In
storage e.xperiments most investigators found that during the first 24
hours there was a rapid decrease in the number of typhoid bacilli,
after which the decrease became gradual, with a persistent: survival
of a few organisms.
The experiments reported give no reason to believe that Ba.cill1t8
coU is any less resistant in water llnd oysters t·han B. tYl'lw8U8.
nound (75) stated that B. coli will remain viable in water for .lit
least 180 clays and thnt his investigations showed 110 multiplicntion
of B.coU in oysters in cold storage at 34.7° F. Furthermore, it was
present in nearly the origin!i,l quantity after 100 days. Houston
(46) found that B.coli persisted for more than 7 days, and CJark
(~7) stated that he recovered B. (Jol-i from oysters stored for 17 days,
which was as long as the oysters lived under the conditions obtaining.
Parsons (personal communication) states that B .coU will not develop
in shell oysters during shipment lJl such a way as to affect the bac­
terial score. Experiments conducted by the Bureau of Chemistry
showed that when shucked oysters are stored at temperatures below
50° F. no multiplication of B. coli or other lactose-fermenting
bacteria occurs. From this observation it would seem thut if oysters
are stored or shipped at temperatures below 50° F., as they should be,
the B. coli score at the end of a period of time sufficient for their
transportation to market will not be greatel' than that Ol·jginally
determined at the source. Howeyer, investigations reported by
Tonney,and 'White (87) showed that IJ. coli did iucrease in shucked
oysters stored at 41° to 46° F. For this reason they recommend a
score somewhat higher than 50 for oysters rrmrkded in the Middle
"Vest. Their observations are in marked contrast to those made by
tbe Buteau of Chemistry. :1'110 optimum temperature for the devel­
opment of B. coli is very much above 41° or 46° F. In .oysters
stored at these ternperatures organisms which find best conditions for
growth at temperatures below the optimum for B. coli will multiply
and produce changes, making the oysters undesirable for the .market
before .there is sufficient change in the B. coU score to condemn them
as unfit for food.
Seveml conclusions can be ckawn from the information at hand
regarding t.he. viability of Bacillu8 typlw81l8 Ilnd B. (!oli in oysters
and water. Regardless of the actual period of yiabjJjty, which can
not be determined for all conditions, the typhoid bacillus can survive
in sea water long enough to infect oysters on the growing grounds
and can then remain viubJe within the oyster long enou~h to cause
illness. The presence of B. coN is a reliable index of pol1ution,asit
also will SUl'nve in water for some time, thus contaminating growing
oysters, and will I'emain villble for some time within the oyster if
kept under proper conditions.
13AOTERIOLOGY AND OHEMI STRY .oF OYST~RS
23
.RS
EFFEC T OF COOKI NG ON BACTE RIAL CONTE NT OF OYSTF.
Compa rativel y little has been reporte d on the effect rroduc ed upon
ents
the bacteri al conten t of oysters by cooking. Clark s experim
stew
for
oysters
of
ation
prepar
ry
ordina
the
(~/') demon strated that
and pan roast does not nhvays kill all the B. coli and streptococci
and
coli
B.
with
d
infecte
were
oysters
ents
present. In his experim
strepb)cocci by floating in sea ,,:ater to which sewage had been added.
num­
The .oysters, which contain ed B. (;oz.i and streptococci in large
­
bel's, were then stewed, fried, and escalloped. In certain experi
bOIling
the
to
t
brough
and
cold
Illilk
to
Illents the oysters were added
POillt. All B. (JoU Ilnd streptococci were killed by the time the milk
ry
necessa
was
it
milk
boiling
to
added
boiled.
When oysters ~were
bac­
to continu e the boiling for at least five minute s before all thewhen
killed
usually
were
cocci
strepto
and
teria were killen. B. coU
tho oysters were fried for two minute s, but they sometimes resisted
sterile
always
were
oysters
ped
escallo
The
s.
frying for eight minute
after they hnd becn cooked for f!'OIll 15 to 30 minute s at oven
temper ature.
The Uepor t of the Boston City Health Depar tment for 1906 (7.n
at
states that, when prepar ed .and served as stews: md pan roasts nal
hotels and restaur ants oysters are not uSl;ally sterile. The additiohelp
heat developed between the time of cookin .... and serving may the
to steriliz e the oyster. Regard less of the effect of cooking upon
bacteri a, it can not be considered 1\ desirab le practic e to eat oysters
from sources known to be polluted.
tent produc ed by heating oysters at
The effect on blLcte rialcon
0
158 0 F. was studied in the Bureau
und
122
n
betwee
atures
temper
were not planne d to demon strate
ents
of Chemi stry. These experim
ed in the kitchen , but to deter­
practic
us
oysters
g
cookin
of
the effect
e to attemp t to Pasteu rize
feasibl
be
llline whethel' 01' not it would
It was soon eviden t that
·izecl.
Pastem
is
milk
as
oysteL'S
d
shucke
for sale as anythi ng
value
their
ed
heating oysters at 12:d° F. destroy
be expected, that
w'Quld
as
is,
ion
cencllls
The
oysh-r.
but a cooked
y imprac ticable
entirel
is
heat
by
.Pasteurizlltion of shucked oysters
raw.
ted
1I11Lrke
be
to
is
t
if t.he produc
This expcri ment demol lstrate dalso that even a temper ature of
158 0 F. applied for ~o .1Ilinutes to oysters in brine will not destroy
At
all such organi sms as the staphylococci and Bacill11>8 aerogenes. al
bacteri
the
of
nature
0
the
upon
effect
iable
apprec
no
is
122 F. there
flora. If sueh orgul1Isms as B. cloacae and B. ael'ogenes survive there
ing
is little hope thut the treatm ent would be effective in destroy
a.
bacteri
B. typlW81('8 01' other disease-producing
can
From the inforlIlati.on at hand it is appare nt that no reliance and
oysters
e
steriliz
to
es
be placed upon the ordina ry cooking process
l'ender those which might possibly contain pathog enic bacteri a safe
for consumption.
RESTR ICTED OYSTE R·PROD UCING AREAS
In order to (h.-tel'mine the fitness or unfitness of any particu lar
ry to make a sanital'Y survey
IU'C:t for shellfish prod uetion it is necessa
y from whieh draina ge
countr
Ulding
sUl'l'OI
the
of
and
of this urea
purpos e of ascerta ining
the
lind polluti on may reach the beds. For
24
TECHNICAL BULLETIN 64, U.
s. ImPT..OF AGiUCULTURE
whethe r Oli not oysters on these beds are pollute d it is usually suffi­
cient to examine the bivalves and the water in which they are grown
for the presence of BacillU8 coli and to make an inspection of
thE:
sewer outfal lsand the surface polluti on in the terrain immed iately
surrou nd!ng the area under examin ation. The eXI?ression." sanitar
survey " 1Il lts broad sense, however, means someth mg more than y
the
mere examin ation of oysters and water for the presence of intestin
al
bacteria. If a genera l surve.)' is to be made of a large body of water,
such as a large river or bay of the Atle:-.o.tic coast into which
the
draina ge of a great muny cities, towns, and smalle r communities
is received, it is necessary to in.clude studies of the methods of sewage
dispos al in these communities, their water supply , their indust
rial
wastes that may reach the river or buy, the prevalence of typhoi
fever there, the popula tion of the towns contrib uting sewage to d
the
rivero! ' baYI and the size of the area drainin g into the body of water
under examm ation. The labora tory tests made in such a survey
in­
clude bactel'iologicul exumin ation o<f water, sewage, and shellfis
h for
tdal numbe rs of bacteria and for the presence of B. coli and
intesti nal bacteriu. Chemical examin ations of the water areother
also
made to determ ine the oxygen demund of the sewage and the presenc
of nitrate s, nitrites , and ammonht: The field survey and the labora­e
tory work Il;l'e supplemented by plankt on studies to ascertain the num­
bers and kmds of protozoa and protop hyta presen t and by hydro­
graphi c studies to show the extent to which tides affect and curren
ts
carr~ sewage to the oyster beds, us well as to leal':n
the dilutio n of
the 1'1\'er or bay water by fresh-w ater stream s or by salt water from
the bay or ocean.
In connection with its regula tory work on oysters from the sani­
tary standp oint, the Bureau of Chemi stry freque ntly surveyed oyster­
growin g areas. For the purpos e of gainin g the inform ation needed
to recommend that certain locations be restric ted fOl< use as oyster­
produc ing areus, it was usually sufficient to examine the shellfis
h
and water for the presence of B. coli and to locate and
the
immed iate sources of polluti on from sewers and privies. study
A great
numbe r of such surveys were conducted by the Bureau of Chemi stry,
and !he results wer~ applied in det~rmining which. areas
be
restl'lCted. The Umted States PublIc Health SerVIce has should
also con­
ducted such surveys, one of the most complete of the reports on
the
sanitar y surveys of rivers and bays bem~ that on the Potom
ac
waters hed by H. S. Cumm ing and his aSSOCIates (30).
The polluti on of rivers, bays, and harbor s along the Atlant coast
with sewage and trade wastes has caused the abando nment ic
of vast
areas former ly used for shellfish produc tion. Such excellent propa­
gating and growin g ground s ascerta in se.cHons of Narrag ansett Bay,
in Rhode Island, New Haven Harbo r, Bl'lClgeport Harbo r, and South
Norwa lk Harbo r, in Connecticut, and Jamaic a Bay, in New York,
have been made unfit for shellfish produc tion by the sewage poured
into them daily from the large cities and towns near by. For some
years this destruc tion of oyster- growin g areas proceeded at such
pace that the situatio n became very serious. In Rhode Island alonea
the acreage rented for shellfish growin g decreased from 21,236 acres
in 1912 to 9,250 acres in 1918. This decrease, 11,986 acres, resulte
in a loss of revenue to that State of $70,375 a year. This shellfis d
h
"
,!\' ,:
'
BAOTERIOLOGY AND OHEMISTRY OF OYSTERS '­
25
ground was !lbandoned partly for the reason that no " set" of oysters
.c6uld be obtained on itBnd par~ly because it was s~ polluted th~t
it was no longer safe as a growmg ground. The faIlure toobtam
a " set" was, in turn, held to be due to :{>ollution with oil and other
trade wastes, although this was not defimtely proved.
What happened in Rhode Island happened also in other States
along the seaboard. If oysters were not to become rare or extinct,
especially in the North Atlantic States l it was necessary to take
steps to improve conditions or to find some way of proceedm~ under
the existing conditions. This stimulated research in the purification
of oysters by floating in clean water (p. 30) and by chemical treat­
ment (p. 33) and alf.-o in artificial hatchin a under controlled condi­
tions. Although the results of these researches have been fltirly satis­
factory, much valuable oyster-growing ground has been lost, never
to bp, recovered. Through the effort.s of river-pollution boards and
commissions organized in the various States much was done to .im­
prove condi tions, but the list of areas still restricted for use as
oyster-producing ground is lopg. There is yet room for much im­
provement in the sanitary condition of the bays and streams adjacent
to cities and towns along the C011st.
.
Realizing the possible danger to health and the undesirability
in any event of marketing oysters from areas subject to contamina­
tiOn with sewage, certain polluted creeks, rivers, harbors, and bays, or
portions of them have been designated by various State agenCIes as
restt'ictedareas for the prOduction of shellfish. The areas restricted
in each State have been decided upon as a result of sanitary surveys
conducted by State officials in cooperation with the Public Health
Service und the Bureau of Chemistry.
Qwing to the fact that from year to year areas ma,Y be changed
from restricted to nonrestricted areas, or vice versa, it IS not feasible
to present het'e a list of those now restricted. Areas which are now
restricted may become nonrestricted upon the instal1ation of properly
operated sewage-treatment plants or upon improvements in the
mdhods of handling sewage in near-by towns and cities. On the
other hand, areas which are at present nonrestricted, may become
restricted if sewage-treatment plants, properly operated now, fail to
maintain the necessni'y degree of efficiency or if an increase in popu­
lation in the adjacent regions contributes additional sewage to the
areas used for oyster production. It becomes necessary for State
agencies, assisted by Federal officials, to make frequent surveys and,
ns It result of these surveys, to confirm the list of restricted areas or
to nIter it as the findings may justify.
In some States the removal of oysters for food purposes from
certain restricted areas is absolutely forbidden. In others oysters
may be taken from polluted areas to be transplanted into clean water
where they must remain for a definite period to cleanse them&elves
by removing ltll traces of pollution. In many States it is permissible
to use polluted .areas for the production of seed oysters only. In
at least one State certnin areas are restricted for the production of
shellfish throughout the entire year, while other areas, which are
less seriously polluted, are restricted only during the season when
the oysters are actively feeding. This ruling takes into considernti'on
the phenomenon of hibernation (p. 26). Although no definiw rul~
26
TEOHNIOAL BUIillETIN 64, U. S. DEPT. OF AGRIOULTURE
~overning
restricted areas apply in every State, most oyster-produc­
mg States have adopted measures to prevent the marketing of shell­
fish from polluted regions.
Information on the areas restricted in any partlCular State may bE)
obtained from the State board of health, the State conservation com­
mission, the State fish and game commission, or whatever State
agency may have the work in charge.
. HIBERNATION OF OYSTE;RS
When low winter temperatures prevail in the water surrounding
the beds on which they are grown oysters enter a state of hiberna­
tion. While in this condition their physiological processes .are greatly
retarded lind, owing to a cessation of feeding, no bacteria are taken "
into their bodies. According to various illvestig-ators, the bacterin
already within t.he body of the oyster when hibernation begins are
rapidly digested and destroyed. Bacteriolog-ists enga"ged in the
routine examination of large numbers of samples throughout the
year have noticed a seasonal variation in the bacterial content of
oysters from the same beds. Bacteriological examination of the
water oVer the growing areus showed that the number of Bacillus
coli viable dUl'in(T the winter was the same us that during the sum­
mer, yet the Bacillus coU score of the oysters was very much smaller
during the cold winter months than during the warm summer
months. Gorham (.~O), in 1910 and 1912, and Pease (69), in 1911,
accounted for this condition by a theory that oysters hibernated when
the temperature of the surrounding water fell below a certain critic.al
temperature.
According to Parsons (unpublished report), hibernation of oySY3l"S
is not exactly the same as hibernation of nonmigratory terrestrial
animals, in that hibernation of the oyster is brought about solely by
low temperature, whereas hibernation of the higher animals is a nat­
ural function taking place at certain seaSO~I1S, even though the temper­
ature may remain rather high. Hib()rnation is a means whereby certain
nonmigratory animals may survive through periods when their food
supply fails and when, if normally active, they might otherwise "carve.
Regardless of the food supply, however, the oyster closes its shell
tight and ent~rs a period of rest or physiological inactivity when the
temperature of the water falls below the critical point (45 0 F., ac­
cording to Parsons). If a period of warm weather ensues after
hibernation has begun, t,he oyster may be stimulated to feed again,
ceasing ·when the temperature next falls.
Recent observations, however, have led to the conclusion that. not
all the oysters in an area will immediately enter into a state of hiber­
nation or will remain in hibernation when the temperature falls
below 45 0 F. Usually some on the bed will continue to feed,even at
low temperatures. This has cast doubt upon the conclusion that
hibernatIOn is a natural function of the oyster and can be relied upon
in adopting sanitary control measures.
Durmg the warm season, while actively feeding, the oyster keeps
its shell open as long as it is undisturbed. Opening and closing the
shell are controlled by the strong adductor muscle attached to each
valve or shell. Relaxation of this muscle in warm weather allows
the shell to remain open in order that currents of water bearing
'BAOTERIOLOGY AND OHEMISTRY OF OYSTERS
~:
27
food may enter between the valves. During the active' feeding period
the minute organisms in the water, such as diatoms and algae, which
COIistitl1te the natural food, as well as the organic matter Ilnd bactel'ia
present as a result of pollution, are carried into the gills of the oyster,
where some of this mllterinl is retained in the mucus coyering the
body. Cilia on the gills propel the material entangled in the mucus
to the mouth of the oyster. The rnpidity with which the cilia func­
tion iSj to a great extent,controlled by temperature. Cold weather
retards their motion so that during the hibernating season practi­
cally no food is carried in. 'That brings about the condition of
hibernation.
It can not be claimed, however, that the shells of oysters remain
tightly closed (ii/ring the whole period that the t.emperature of the
water is below 45° F. To satisfy their demand for oxygen, even in
this physiologically inactive condition, the oysters mllst occasionally
open their shells. "'hen this occurs some food passes into the cavity,
but investigation has demom;;trated that the quantity is veIl small.
Albel't Mann, of the Bureau of Plant Industry, Unite States
Department of Agriculture, found that the stomach contents of
hibernating oysters are pructicully destitute of diatoms. He con­
cluded thut eHher the oysters were physiologically inactive or
the supply of diatomaceolls food was very low. Parsons further
demonstrated, by the use of dyes in the surrounding water, that
oysters only occasionally open their shells during hibernation for the
purpose of obtaining n. supply of oxygen.
It is in order now to return to the rather startling results of the
bacteriological eXllminations of oysters which first focused attention
upon this so-cnJlec1 hibernation. In the investigation l'eported by
Gorham in 1912 (40) two oyster beds in the Providence River, R. I.,
and two beds in the "Yarren RiYer, R. I., were studied. On one bed
from the Providence River oysters colle.cted in February, when the
temperature of the wuter was 33.8° lI'., scored 0, and those collected
in May, when the temperature was 59° F., scored 500. At the time
of both examinations Bacillus coli was prL sent in 0.0001 cubic centi­
meter of the water. Oysters collected on a bed in the Warren River
in February, when the temperature of the water was 32°F., scored 0,
although the water over this bed contained B. coli in l-cubie-centi­
meter quantities; and those collected in Jate April, when the water
temperature was 52.7° F., scored 500, B. coli being found in dilutions
of 1 to 100 of the water.
'
In 1916 PaJ:sons find Farrar (unpublished report) found that
oysters collected during November and December from grossly pol­
luted areas in .Jamaica Bay, Raritan Bay, and New Haven Harbor
scored below 50, although such oysters examined during the non­
hibernating period scored 500 or more. Owing to their proximity to
the sewer l some of the oysters with low scores were covered with a
deposit ot filthy, foul-smelling mud. Obviously such oysters could
not be marketed, regardless of the low scores.
In order to determine whether hibernating oysters would become
polluted when floated in sewage-contaminated. water, Parsons placed
hibernating oysters from Raritan Bay, scoring 1, in LupatcongCreek,
which was polluted from the sewage disposal plant at Keyport, N. J.
These oysters remained for six days in water at 32° to 34° F., con­
taining JJ;. 'coli in 0.1 ,cubic centimeter, ,and sometimesQ.Ol cubic cep.ti..
m~ter, quantiti~s, without an ,increase in s(;ore.
,
In ,Ollder ,Ito show the contrast between the score of hibernll-ting
and that of nonhibernating oystl:)l;S, ,Parsons prepared a summary.o.f
,the resultsP! his examinations of oysters from various beds~Qnducted
thrQughout the, year. (Table 8.) The contrast between winter .,and
swmnerscoreo would be greater had not a large number of .the sam­
ples ,been collected at the beginning and end of hibernation,
TABLE
8.-Effect Of Mbernatioll on Baoillus coU score
Score
Number
with
o(s.lm·
wllter
pies ilX' 45° F. or
omlned
lower
Ded -,---,--~"---------------I---
~~ft~~ .g~~:~: i::::::::::::::::::::::::::::::::::::::::::::
New .Havell'Harbor, COlln. ' ••••••" .•••••••_••.•••••.••••••_•.
Hllmpton Dar, Va.'••••••••.••_.••.••••••.••••••.••.••._•.••••.
Score'
with
.'wllter
Numher'
oCsam·
,pies ox·
:noove
45° F. ,
amined
- - - - - - -,- '-.
S4
14
9
18
3
82
3
7
1
12
250
'260 19'
6
350 140 \ 'Uestrlcted bed.
The.lo;W,est 11ndhighest scol'es~olmd in ,oysters from certain lqca­
tions., with the date and the temperature of the water at the, time the
samplesiWel'e collected, are given in Table 9. These resultssho:w
that, ,the low scores of winter are ilot clue to any diminution of !.the
number of colon bacilli in the watel'oYel' the beds, thevarJation ;ill
the B. aoldconnt of the water being only that due to tides" curl'ents,
wind, and unusual pollution fr.om land sources as a result of hea:vy
rains"
iVAnLE 9.-Sea~/01H1l
.,
variation in Bacillus coli scores ,of ousters trom polluted
,
(/reas 1
Minimum score
Maximum score
"
.
Temper· ature oC Date when water
found when
found
ANa
"
illmnlcn Dar, N. Y.:
'Big Channele ..••••••••••••••
Islond Chunnel.. _••••••••••,
Flshklll ChanneL •••••••••••
Pumpkiru Patch••••• , •••••••"
Rume Bllr _•••.••••••••••••.•
• 'DeachOha\lneL•.•••••••••••
Silyerlllolo••••••• c•••••••••••
GrusS Hassock •••••••••••••••
,Broad ChanneL.__•••••••••••
Irish ChimnoL •••••••••••••••
. Horm ChlinneL~ ••••••••••••
Old Swlllo ChanneL •••••••••
RarltnnBay, N. Y.:
Score
Score ------
,'., Ded
~:~ l:::::::::::::::::::::::
1031 •••••••••••••••_•••••
.' ,Ded
;i:gs~iih(rIi86:::::::::::::
996."....................
2
4
1
0
1
2
1
0
2
Ii
Ii
3
5
23
0
4
0
4
Bed 891. .• ~ •• : ••••• ~ ••••.•. ~.
3
.Point •••••••••••••••.•, ••••••• '
Hampton Bar, iVlI.•.••••••••.••••
2
0
New Baven:Harbor, Conn.: City OF, 44
32
aLa
31.. 5
31.5
30.5
46
30
42
31.5
32. 5
34
OF.
Mar. 31,1914
Jlln. 21,1914
Jlln. 5,1915
••••• do~ •••__••
•.••.do•.••••••
Jan. 23,1914
~\pr. 15,1914
Jan. 23,1914
Nov. 20,1914
Jan. 5,1915
Jlln. 26, 1914
Mar. 17,1914
600
600
600
600
600
600
500
'410
'140
'320
140
140
~8
Jan.
Nov.
Jan.
Jan.
Jan.
Dec.
Jan.
28,1915
17,1914
28, 11115
18, 1915
28,1915
22, 1914
28,1915
410
230
320
410
410
320
44
32
Nov. 'n,1916
Feb. 12,1017
500
410
38
43
38
34
38
.40
Temper·
ature,of.
Date when
water
found
,When found" 500
72
72
7:.1
67
72
70
64
62
70
July 14,1915
MI\Y 14,1915
'Do.
Sept. 16,' 1914
May 14,1915
Sept'. ,8, 1914 Sept. ~24, .J91ji
MIIY 18,1914
~t.ij,1014
64
ay 2O,lOI~ June "1,1014 Do. '75
76
July J5;1915
Aug. .10;1914
64
·64.5
0,
';])0. ,
'76
69
75
76
70
June 24,1914
July 15, 1915 Aug. 10,1914 Do. 52
53
Nov. 5,1915 Nov. 15; 1916 "
, Compiled from unpublished report ofP. D. Pllrsons, 1017.
BAC'.l'ERIOLOQY .AND CHEMISTRY. OF OYSTERS
,t\A
t~V
From the in:t'ormlttion at hand it is e.vident that low temperatures
of the sea water surrotmding the oyster beds bring about a resting
or dormant condition in t.he oyster. This cessation of fcedinS', in
turp., proc!uces II concli~ion within the oyster approaching stef~ty,
the bacterIal content bemg reduced to almost zero.
. ' '._
Oysters on bt\ds in the wnters of New York, Connecbcut,Rhode
Island, and ~I!lssaehusetts usually go ~to l~bernat.ion ,during.tl~e
latter part of November und remam untIllll:te m AprIl. The oystet;S
in 'lower New Jersey hibernate !l little luter and I'e,mme .normal
activity a little earlier in the spring. The oysters 'in Marylitnd. and
Virginia may not go into hibernation until !l month later !lnd ·the
period of hibormttion is often comparatively short.
The filet that during hibernation the bacterial content of oysters
Imd the possible menace to health from the consumption of shellfish
are reduce(l to a minimum has been applied by some States to regiIla~
tions for sanibtry control. Oertain aToas on the border .line between
a gl'ossly polluted Ilnd n. clean conclition are utilized for oyster pro­
duction between December ILnd March, when the temperature .of the
water remllins below 45° F.
.
It must not be Ilssumed that becnuse hibernating oysters are. bac­
teriologically clean within the shell the sume is true of the outside
of the shell. Deposits of mud IlIlel filth collect on the shells of
oysters growin;? near. sOUl'ce~ of pollution. Upon shucking,. this
mud and ruth find thelr way'lllto the shucked product to COJ;lstttute
areal menace to health. The number of intestinal bacteria ii} the
'Water is no smaller during the cold weather than during the warmer
seasons, and the outsidu of the shell n:uy be grossly contaminated
with bacterin that mennce the health and with other material1lhllt
offends the sense of decency, even when the oyster within the shell
is clean .
.Althou~h some States permit the use of oysters, during hibernatidn,
from slightly polluted grounds, other States, in spite of tne well­
established fact of hibernation, do not allow oysters to be taken for
sale from areus cluring the winter unless they are fitfol' use during
the warmer sensons. Recognizing the fact that the water over the
beds is no cleaner in the winter thun in the summer and that the
mud and filth on the shells will contuminatethe oysters· during
shucking, the State of New York condemns for oyster production
throughout the yenr all areas that are unfit during the 'nonhibernating
seasons.
. ,
Data on hibernation prove that oysters, at least those in nortliE!rn
waters, enter into n state of physiologicrJ inactivit,Y when the'tem­
perature fnlls to 40° to 45° F. During this perIOd of inactivity
the bacterin1 content of the oyster is reduced to 11 minimum. Whether
this phenomenon should be taken advantage of in any sy-sternof
sanitary control is 11 question which has not been satisfactorily agreed
upon 'by ull State and Federal ngencies. Even admitting the facts
l'egar¢ling hibernation as here set forth, it is probahly safer and
wiser to prohibit the use of oysterR fromarells at any time of the
year unless those areas are fit for produetion during all times of the
year.
,
.
..~
'30
TEOHN I0 AL BULLE TIN ,"
"'*J U. S. DEPT. OF .AGRICU LTURE
PURIF ICATIO N OF OYSTE RS
TRANSP LANTIN G
When trnnsp lanted to clean water, free from contamination with
uctively feedinO' oyst.ers that have become pollute d on the
w'owin g urens c1ellllse tIlemselves wjthin a l'eusonnbly short period
The len~th of time depends primnr ily on the purity of the wate. 4
r.'
While tne oystel's are feeding Ilcti vely the gills nct liS ufiJ.ter
to
strain out some of the llllLterinl that mnT be brough t in by the
or
8 gnllons of sen, water which pnss throug h each oyster daily. If 7this
sea wuter contnins sewage with large numbe rs of intesti nal bacteri
n,
some of the microo rganism s are entrap ped in the mucus on the body
of the oyster and al'e then transfel'l'ed to the nlimental'y trnct
by
the cW'rents of water set in motion throug h the action of the eilin
on the gills. When oysters thus pollute d are floated in clean
sea
wuter contain ing no mtestil lal bacteria, or very few, the micro­
organi sms Illr'eudy pl.·esent Ilrc elimin ated und no Ill-,We are ingeste In this wily the oyster pmifie s itself in a rel1llll'lmbly short time.
d.
The rapidit y of this cleansing pl'ocess llider vllryin g conditions
hus been investi gated by mllny bacteriologists, F(ll' seyeral reUSOl1!
Itis impol'tunt to know the minim um time in which a proper clelms­ ;
ing cun be effected ufter tl'llnsplantat.ion. InjUJ'y may result
oysters held too long uncleI' unnatu ral conditions. If the oysters to
Ill'"
flouted in wuter of lower density thun that in which they wer'~
grown, blonting will take place. If prolon ged, this results in their
deuth. The undesi rability of using for .floating purposes: oVel' long
{leriods, ureas that mlly be lJeeded fol' gTOWing oysters is appare
In cllse of Il demand for shipme nts on compal'lltively short notice nt.
J?,rowcr or dealer llIlISt know tJ\e minim um length of time necessath!!
ry
101' the purification of any pollute d oysters he mny be obliged to use,
'1'herefor'e, the .impor tant considel'lltion in the in restiga tions under­
btken hus been to detel'luine beyond doubt the time necessary to effect
a propel' cleunsing withou t prolon ging the l)eriod to the point
where
jt becomes injurio us to the oysters 0.1' expensive to the grower
Reglll'dless of expense and inconvenience, .howe"e1·, the primur y s.
ject of such tl'llnsplantillg must be to rid the oyster of all tracesob­
of
sewage polluti on.
In Europe , Klein (21), Hcnlm an und Boyce (4~), and
one
(5.1), and 111 the United States, Phelps (70) and Round .Tohnst
(75)hu ve
,investigllteel the ability of oysters to cleanse themselves.
In Table 10 are pI'esented the dutll obtained in thejnvest.igatk'!1s 011
the effect of transpl anting pollute d oysters to lmpoll uted water
con­
ducted by PUl'sons in Connecticut, New Jersey , Ilnd Virgin ia. These
indicut e thut 24 hours sutlices to clelmse poUuted oysters if the water '
to which they are tl'lmsphmted is really clean Ilnd if the temper ature,
the salinit y of the water, and the season of the year are conducive
IlctiYe feeding" Such conditions are usually found with difficulty, to
ordina rily the creeks or bays used for tt'ansy lanting are subject as
oCCllsional pollution during the .floating pel·joe and the salinity of to
the
water of the C1'eeks may change greatly with the chllnge of tide,be
corning pructicuUy fresh nt the end of the ebb tide. The effects ­
of
occllsional pollution aUld of changi ng salin ity Ilre seen in the results
vf the floating expel'jments in New Y orIc Stute, at Hussock
Cl'eek,
~wage,
31
BAo;rElUOLOGY AlfD CHEMIS;rRY OF OYSTEUS
Bigg's Crcek,Jolm's Creek, GalTctson's Creek, Winant's Pond, and
Flatlunds. Here the reduction jn score WIlS grently retarded. It is
apparent that repettted clennsing with occasional contamination ulti­
mately bl-ings about a purification of the oyster, although it is some­
what delayed.
TAIIU: lO.-RclIllltSl o( i.raWlI/hwting 11O/tlltcd oy,~tfJr8 i,~ unpolluted water'
Score
Ded
Dille
l'IIO',II'I'!~(1 '::~:,':!~'
will or
v
Slllllllty
01 wnter
ne~!II'
1I111~ 01
period
I)nu,'
EII.t Hnvoll Hlver ..••__•••••••__ October, 101tl••• _. {
~ ......... _~_ ..._..... Novemher, 1U1I1
01(\ .I'oillt Comfort, VII••••____•__ ••••• do ............
.1hlckroe 11ench, \r n
Jl8S5uck Crook ' ......._•• ______••
'.
{~~~l~f,~~~~~~ ~~~.~:=
Mnr, 11115.....___
1Ilgg'. Crook '._______............ OCloher, 101·1. ....
J"hll'. Cro"k ' ..... ____.....___... ••••••10•..••• _..__..
Garretsun's Crt'Ck 1 ____.......... __ ..... •• _••(\0....________
Wlnllnt'.l'llml'_ ..._____________ _____do..._________
jo'llItflln(\s ' .._____________________ ____ .tlll. __.-----___
oJ,'.
I
lift-lill
5[.-5li
"
M·1i7
liIH,!
I
I
a
14
:I
i
4
50-5~
110
72
iii
40
.[
~u
"
.1\1
4
3
60
60
.sp.f!T.
1. OW
320
End of
II0r1od
14
32
I.OW
I, om
I, O~I
1.021
1.02'a!
1.00l"l
1.021
:!20
3, Z.JO
I, ~IIO
1.02'~
1.02'~
:I~'O
32
Ii
23
:120
320
41
.2:1 140
140
23
1. tr!".!
1. {)IS
l.lI'2U
1iOO
r.l1O
230
:120
14
4
41
32
~'3
, Compllell from 111It1l suhmlUod hy 1'. B. PllrsUIl. to lIuroau Ilr (,homlstry, 1017.
I Tho wllter to which tho uystors wore trllllsplllllted WIIS .uhject to i)cClL~fonlll t~mtlllllluBtion during the
perlo<l.
wlltor to which tho Ol'stors woro tmnsplllntod W'L~ fllfrly clenn, but becullle Iresh nt the end or the
ohb tldo.
n()lIt1n~
J 'I'ho
The effect of o(.!casiOlllll lwllution dm'ing the floating period was
n'ry well illllstmted by experiments conducted by Furrar (unpub­
lished report) Ilt Block Islnnd, It 1. Polluted oysters were trans­
planted to New Harbor, which is ordinal·.ily free from pollution. At,
the time of the experiments the. waste from some wllrships mool·ed
neltr by polluted the water, Conseqlll'ntly, there was no redlldion
in the /)acitz.1l8 coli. score during thc first 48 hours. The ships then
depnrted and durin:.r the following 24 hours a purification of the
oysters wus aceomplishecl Fa.rrur's experiments dell1onstl'ute the pos­
sibility of cleansing highly polluted oysters within 48 hours. Oysters
Wel·e artificially infected by tlonting netu' a sewer for several days
until scores of 50,000 and 140,000 were obtained. Floating for 48
hours in clean water reduced the scores to 5 and 4. This wus a.
severe test, as oysters do not ha "C snch high scores natn~~ally.Oyst(lrs
grown so near the sewer would be smothered by depOSIts of mud and
filth and would be rendered unfit for IDarlmt.
In experiments conducted in 1918 at '\Vicldord, R. I., Hunter found
t hilt tlH~ score of oysters when trnnspla,nted to clean water wus .reduced·
II'om 5,000 to 14 and from 410 to 32 in 5 duys. In Imotherexper:i­
ment 96 hoUl's wns sufficient to reduce scores of 410 and 230 t<114 and
23. At certain times the water of 'Wickford Harbor contnined B.
GOu. in l-cubic-centimeter quuntities and at other times no B. coli
could bt· found in the 10-cubic-centimeter qunntities. From this
it is evident that the water c.f 'Vickfol'd Harbor wns lIot uniformly
clenn but WIIS subject: to periodic contamination. This accollnts for
the fnet that, fl'om four to six dnys were required for the oysters to
clennse themselves.
32
TEOHNIdAL BULLETIN 64, U. S. DEPT. OF AGR:IOULTURE
Although it is true that polluted 'oysters will cleanse themselves
when transplnnted to clean water, it is equally true that clean, un­
polluted oysters will l'a.pidly become polluted if floated .in sewage­
contaminated water. Data taken from a report submitted by Par­
sons in 1917 sho'wing to what extent this pollution of oysters occurs
are presented in Table 11. 'When Bcu.:illus coli was present .in 0.01
cubit! centimeter of the water of New Haven Hal;bor, Conn" it re­
quired only two hours to incl'ease the score of the oysters floated there
from 14 to 500. Hibernating oysters floated .in Lupatcong Creek for
seven days did not increase in score. This fact, together with the
data given by Round (75) showin~ that the score of hibernating
oysters did not decrease when tmnsplanted to clean wllter, lends fur­
ther support to the theory of hibernation or physiological .inactivity
of oysters at low temperatures.
TABLI!l
11.-Reslllts Of
tr(I1I.~[JI/lllriIlU
·/Il/poUul.eu ollsters ·in pollutc{[.
br(!cki~h,
11J</,f,cr'
Score
ped
Date
Time
lIouted
-.".
Enst Rocknwny Creek, N. Y ___•• October, 1fll4.____
.Lupntcoml Creek, N. J __________
New Hnven Hurbor,' (101111_ . . . . _
New,HuvoII lIurbor,' OOlln ______
Lupntcong Creok,' N. 1..________
June, 1915......._____
October, 1016_____
November, tUIG__
Mllrch, 1915______
..
_'.-,--,.--
DaU8
1
6
-(,
-(,
7
TOInllcr-
nturo of
wnter
Snlinity
ofwlltcr
Begin­
uing of
period
Endur
period
- - - - - - - - -- - OF.
Sp. gr.
60
70
56
5()
..0
1.013
(2)
1.010
1.010
(I)
{
{
3
5
32
23
(0)
3
14
23
/ill
140
500
41
500
5
I Compiled from dntll submitted hy 1'. B. J'nrsons to l111rmlU of Chemistry, 1917.
I The water in this creek hlld [l salinity of 1.017 lit the elld of tho nood tido nnd wus nearly fresh wliter
nt tbn end of tho ebb tide.
I, B. coli were prescnt ill 0.1 cubic centimeter of tho wntor of tho hnrbor whero lIoating look pilioo.
• 11. coli woro presellt in 11.01 cubic centimeter of tho wlltor of the hllrbor whero OOlltillg took plnce .
• Tbese oysters were in !l hihoflllltillg condition. INotgh·en. Fl'om all the investigations conducted it is apparent that polluted
oysters can purify themselves when transplanted to unpolluted
waters. Although the lellg'th of time necessary for such purification
can ,not be detel'mined definitely for all locations from 'the results
of the studies already made, it can be concluded that such purifica­
tion is ,possible withIn 24 hOlll'S jf the conditions are exactly right
and that seven days will suffice, even whell the water to which the
oysters are transplanted is subject to occasional pollution. Much
discretion must be exercised in applying to sanitary control the.
knowledg;~ that oysters have the power of self-purification, Before
the merit:; of any location can be passed upon, study must be made
Qf the water Imel attention must be given to the sltnitary features
of the surround.ing country. It is suggested ·that transplanted oysters
remain in the clean water for about seven (lILYS. If the water is
clean, as it should be, and if the conditions are such thilt the oysters
feed normally in freely ciI'culatin~ water, this period, will allow a
margin of safety over the time absolutely necessary for the cleansing.
This margin of safety is necessary because of tile impossibility of
controlling ull the factors involved in the process. Whenever pos­
"
BAOTERIOLOGY AND CHEMISTRY OF OYSTERS
33
sible, Bacillu8 coli scores should be obtained on the transplanted
-oysters before they are taken up for the market, and no .oysters
should be taken for sale .until the score has been reduced below 50.
As oyster samples from one location sometimes vary, there is dang~r
.that the results of one examination may be misleading. Tl)erefore,
the low score should be. obtained on two or more samples ·before ·the
oysters are considered fit for use,
lf the wllter in which the oysters are transplanted is clean, if the
currents and .the arrangement .of the oysters are such that there is
free circulation of pure water among them, and if the temperature
is favorable for active feeding .and for discharge ofpoUutingmaterial
~rom the shellfish, this ubility. of oysters to cleanse themselves ,can
be used to help solve the problem of how to utilize stock from pol­
luted areas that have been condemned.
CHLORINATION
I
The lack of natural dean waters, suitable for the purification ·of
oysters by flouting und within a reasonable distance from the polluted
ureas, made it necessary to search .for some other practical means of
purification. For im;tance, pollution made it necessary either to
ablmelon Raritan Buy, N. Y" un excellent growing urea, or ito find
some meuns of Ilrtificial purificution, as no near-by waters could be
used for self-purification. This need for a method of artificial puri­
fication, which existed also in other localities, led to the development
of the chlOl'ination pl'Ocess by W:,ells, with the assistance of 'repre­
sentatives of the United States Bureau of Chemistry, the United
States Public Health Service, the oyster industry, and the New York
State Conservation Commission (~3, 101, HIE, Hj3, 101,.,105).
The biological principle underlying this method is the same as that
upon which self-plll'ification is based. In fact, the two methods are
the sume except thlLt, in the method developed by Wells, by the use
of chlorine us a sterilizing agent, clean water is provided for floating.
The ability of the oyster to cleanse itself by washing out impurities
w.hen floated in clean wlLter is made use of in this method under
cRI'efully controlled conditions.
Wells, experimenting ill 1914 and 1915 at Fisherman's Island,
Va., found that if oysters were floated in watm' containing an excess
of ft'ee chlot'ine they would close their shells, permitting sterilization
of the exterior, !md that when the excess of free chlorine was greatly
diminis!:.<ed they would open their shells again, ·thereafter cleansing
themselves in the sterilized sea water. In 1916 this chlorination proc­
ess was tested, with the .assistance of Parsons of the Bureau of
Chemistry, at New Haven, Conn. In 1920 the Public Health Service,
the B\ll'eau of Chemistry, and the New York State Conservation
Commission cooperated to demonstrate the process under commercial
conditions. ThIS demonstration, which was followed by nn indorse­
ment of the method and certification by the New York State Con­
servation Commission of a purification plant at Inwood, Long Is­
land, is reported in detail by Carmelia (~3), Polluted oysters in
large lots were spread in great wooden floats and covered with ·clean
sea water. Calcium hypochlorite, in such quantity that free chlorine
was available in from 4 to 6 parts per mill.ion,
distributed over
was
78955°-28-3
:3'4
TEOHNIOAL BULLETIN <M,
u. 'S.
DEP~~/:t)F AGRICULTURE
tlie floats 'by means of' hand-operated wooden tpaddles.The :quantity
?~. chlQrine needed was determined '~y. the quanti~yoiorganic matter
mthe water. The greater ,the quantIty of .orgamc matter the greater
~is·the· need for chlorine. More chlorine can be used ,than is tolerable
·i~drin;kii.lg water.. From 20 to 30 minutes.after the addition of,tnp
~hyPochlotite the water was tested with orthotolidine for free chlorine.
The 9ysters were then left undisturbed .during a "~rinking" periqd
:of6hours. At the 'end of this period the floats, were agam treated
with ,chlorine ,as at firSt, after which they were left for from 12
.to 18 :hours. This gave a 24-hour "drinking ".period, ,at the end
:6f'which the oysters were ready for the market.
The hypochlorite first sterilized the water in which the· oysters
were placed. For a short time this excessive quantity of ,chlorine
was so irritating to the oysters that they repeatedly and forcibly
ejected water from between their shells. This action removed much
mud, sand, and other organic matter. The action of the chlorine
;a:lso loosened the ,organic matter on the exterior of ihe shells.' ,Left
'undisturbed, ,the oysters filtered the sterilized 'water through thei·r
igillsand alimentary tracts, removing ma.terials which served to
,moderately pollute the floating water. The second treatment with
calcium hypochlorite again sterilized the water, in which the ()YBters
'were: then floated for 18 hours.
.
In these experiments ,a reduction of 90 per cent of :the Baci11tuscoli
content of oysters scorin~50 or more ·was.obtained. Accol"ding to
Garmelia (933), a reductIOn of 99 per cent ,of the Bacillus coU:in
oysters scoring 500 will produce .a score of 50, bringing the oysters
only to the passing mark and allowing no margin for ,safetyCJ'able
12). He believed, therefore, that no oysters ,which ·scored higher
than 230 or 320 should be purified by this method.
TABLE
12.-Bactcr'iologioal rc,~ults ot/o/lster purification by hypochlorite ,11roo08s 1
Source
________
Run Quantity
No. oC oysters
trea ted
AvenJl\o BnclUlU
col. score
Average
redUction
oC
DeCore
ACter ' B~cilh,"
treatmontltrentment coll.:score
I
~-----~II-------------'
Raritan
Day botweon ---_.__:_
Groot Kills
and Princess Bay, N. Y __
Do_____________
-- ---_____________________
,Jumaicn Day, Dig Channel, C1arnarsio, N. Y _________.--- .
Raritan
Day betweon Grent Kills Bnd Prlnccss J3BY,
N. y__
Do___________________________________.-__________
))0 _______________ ,----.--------- ___________________ _
Do_________________________________________________ _
,Do__________________________________________________
Rarltnn Day, 01T South Beach, N. Y__________,________ , __
Raritnn Doy betweon Grent KIlls alld Princess Dny, N, y_
Raritnn Day IIcar Grent Deds, 1.ight Amboy, N. Y_____ _
JBmalcn' Day, Sweet Water nron, nonr 1nwood, N. Y____"
Jamaica Day, Dig Ohanllol, carnarsie, N. Y__ ~ _______ ~ __
Btuhtl8
1
2
3
46
4
50
'20
60 .
5
150
6
,7
8
9
10
11
12
13
23
50
230
14
14
5
60
50
60
15
,60
4
14
41
2
25
20
15
320
320
320
2
5
:23
4
4
3
2
,5
4
{, .
3
23
_'_
Percent
.91.3
00.0
:00.0
7IA
71.4
40.0
'50.0
64.3
00.2
50.0
,9@. 7
OIl. 0
02. 8
IReprinted Crom Carmolia's roport (fS).
As a result of the indorsement by Federal and State 'authoritIes of
the chlorination process as an .efficient and practical method of cleans­
ing oysters, a plant for this purpose was installed on a commercial
:b~sis !J,t Inwood,.N. Y. (101, 10tJ, 104). At present the State of New
,3&.
YOrJ.r .d~S, notp~l:mit! the .ta\dqg~ofo~st~rs froqlbeds :where B. CGl~~!
scores of over 50 are obtained except m the .summer for the purpo~'
of. t<J;a~spl~nt!ng. This reg;;iation w~s p.u,t jnto .effect .0.8 .a:;·,~o.f~ti·
ln~a$qre, hut Itsena9j;m~t .did aw.ay wIth the need for a;c41Qrmating
p~an~~s.uch :0.8, (~e ,oq.~.at, In woop" ~ hich has ;been clisma,ntled,.How: i I
eV~f,;~v~aloYl3ter pompan'i~ (Lt We.st,Sayville, N..Y.,~re now usi~g,
the chlorinating metiho!l up<mmQst, if not all, of.the.py8ters)~~dled.
bytthem.
.
'
.
.' ,
lIt its· control of the chlorination process the New York State"Con­
servationCommission has issued, the following reg~lation (6.7).: .
. .Raw! water to be llUritled for use in drInking, flouting, or tile 'waterstorage:
of .oysters shuU.huve unlnitiul score ,of not more thun 5 (5 portions ,of the water
HUJpple t{J. be tl'eated us 5 shellflsh in securing this score). Said. watershali
have a salinity sufticient to ",rive a specific gravity of not leSS tuau 1.007 at
15" .0, aild shu1l be treated with liquid chlorine, calcium or sodium ']IYpO­
chlorite, or 8i 111 liar cblorinecompounds prodlicedby electrolysis. If the flll·
und druw ·method is used, sUfficient cblorine or its compounds in -one of the
forms qlpntioned shall be added. to the wuter to se~ure a free chlorine content
of npt less than 0.5 parts per million· in !tny palt ·of' tile tank fifteen minutes
uftcr filling is complcted. If tbe continuous fio,,, method is uSed, a control re­
IlctionchullIher shall beprovlc1ed 'through which the 'wllter shall ibe passed
bef9re-it ,enters the oystel' storllge 'basin, SucbchllIDber shall be twice las long
as it Is w.lde a11(1 not lel:1s thun 4 feet decp,properly baliled and huving a. !le­
ten/tion,period of not less than tlfteen miuutes. In using this method, su1ficl~e
chlorine or .ft.':! COlli pounds in one of the forms mentioned shall be .added to the
water to give Ii free chlorine content -of not ,less UlIlnO.5 parts per million to.
tile Mlater collected· from the outlet of such reaction tunk ,before It enters tile
tlWk in which the oysters are stol'Cd.
The ·chlorination method is ,efficient if carefully supervised and
properly conducted. It should be as carefully supervised 'as is ,the
Pasteurization of milk. Perhaps more important than the ,quality ,of
the oysters used, the purity of the water, the strength of the ·steriliza­
tion agent,or the length of the " drinking "period,are the intelligence
! ...1 care shown by the operator. . It is absolutely necessary ,that the_
'ator have enough experience to .understand the principles ,under­
i ong;.the process and to be able to interpret his results as they are
Jbtained. '
,
The ,experiments of Krumwiede, Park; and others (51) indicate·
that, under the experimental conditions l the chlorination treatment
is not reliable in ridding ,badlycontammated oysters .of viablety­
Jlhoid 'bacHli. They conclude that "the chlorination treatment of
contaminated .oysters will result in a marked diminution in ~he_
number 'of B. t'Yplw8'U8, but even six successive treatments may .not
rid ;,the,oysters of the contamiI?-ating pathogens. TJ:te pl:ocesscan
not be' recommended ,therefore m any sense as a reliable means of
"sterilizing' 'contaminated oysters and thus rendering ,them safe ~or
cOnsumption." The experim~~ts uJ?on which t~is conclusion.'Yas
based:·:represent ·extreme conditIOns, m that typhOId feces pontammg
enormous numbers of bacilli and large .quantities of organic matter
were Ildded to relatively ismallvolumes ·of water in whichoystel's
were floated. This w.as followed by the use of such qUllntitIes of
(;hlorine that 'it is possible tbatthe normal functions .of theoysteriin
pur~fying. itself, were interfered ,!ith. There 'i~ s~ill plent~ !Jf 1'('11.­
!;lon'l'o. bebeve that oysters contam.mated .under nafura} C?ndltion~ on
beds not too grossly polluted WIth sewage may ibe -pul'lfie.d by ,the
(·l!!orinationproc~ss. It .has not be~n recommended that attempts.be
.
'
36
TECHNICAL BULLETIN 64, U. a.DEPT. OF AGBIOULTURE
made to chlorinate und to purify for use I1S food grossly polluted
oysters.,
At some shucking houses where surplus stoCk is stored in tanks or
floats until needed, it is considered good practice to add calcium
hypochlorite .to the water jn which the oysters are stored. 'This is
done to prevent contamination between the time the oysters are
taken from the growingureas and the time of shucking.
At first ,thought, the chlorinatitm of oystm,'s may not appear de­
simble. It is suggestive of an attempt to render fit, by chemical
disinfection: It filthy and polluted product naturally unfit for use.
Such objectIOns to chlorinated oystel:s, however, are based on a lack
of understanding of the process. It is becoming as difficult to pro­
duce oysters entlrely free from pollution us it is to find sources of
drinking water tl1at is naturally fit for use. In making drinking
water clean and safe mechanica-l111ters and chlorine are used. There
is no objection to this in the minds of the users of such water.
Similar use of chlorine is made .in the artificial purification of oys­
ters. :Furthermore, to quote 'Yells (103), n this lneUlOd of purifi­
cation consists of nothing more than assuring condWons of cleanli­
ness under which the oyster cnn, by its natural function, remove !lny
pollution l'ecl'ived frol11 the water."
The treatment with chlorine l)l'oduces no change in the appearance
of the oyster nor in its flavor. The calcium hypochlorite reacts
with the salts present in the sea water to form calcium carbonate
and sodium chloride, both of which nre normally present in sea
water. It is no doubt true that, in oysters scoring not too high
originuUy, t.he finished product uftel' chlorinat.ion is cleanerbactedo­
logically t han some of the oysters marketed direct from the growing
lu'eas. It may be that sooner or later the opinion of the advocates
of this process willprevuil aml that chlorinntion of oysters will 'be
regllrded in the same light as chemical treatment of drinking water
and Pasteurization of mille. At present sufficient investigational
work has been conducted to demonstrate that, when properly carried
out, the chlorination .method is not objectionable and offers a means
of :rendering deun, safe, and fit for mnrket,oysters which otherwise
couLd not be used.
As its efficacy depends upon the power ·of oysters to cleanse them­
selves by "dri'nking" the clean water in which they al'e floated,
it is obvIOUS thnt this method can not be applied to shucked oysters.
However, snme dealers are adding chlorine to the water with which
the oysters ath wushed in the shucking house. The proponents ,of
this method of cleansing shucked oysters claim that about 10 parts
per million of free chlorine, available in the wash water, prevents
any increases in the Bacillus coli score and in the total numbers of
bacteria during washing and handling subsequent to shucking.
FLOATING :OYSTERS IN THE .SHELL
For a grent many years before the passage of the Federal food and
drugs act it had been known that floating living shell oystel's in
brackish 01' fresh water would bring about great changes in the pro­
portions of solids and water in oysters. In 1887 and 1888 Atwater
(9, JO, 11, 1~) discussed the application of the principles of osmosis
and dialysis and presented data to show the extent of the changes
,
BACTERIOLOGY AND CRE,MISTRY .OFOYSTERS
37
taking place during floating. He directed attention to the fact that,
as a result of floating, there was a gain in volume and a loss of soHds
and salt and that the appearance and flavor of the oysters were greatly
changed. In spite of the knowledge that such changes, amounting to
adulteration wIth water, were produced in oysters by floating, this
practice was continued.
In the face of claims by .certain oyster shippers that it was neces­
sary to float shell oysters morder to cleanse them, to remove sOine of
the salt thnt they might stand shipment better, .and to meetu popular
demand for a plunW "fat" oyster, it was nece!isary for the Bureau
of ChemIstry to .do s6me investigational work to determine whether
or not there was a relll need for floating and .to ascertain to what
extent adulteration occurred 'when oysters ""ere floated.
As a result of this work and of hearings held in 1909, Food In­
spection Decision 110 (88) was issued. This decision stated, among
other things, th!Lt oysters are adulterated within the meaning of the
act if they have been subjected to floating or "drinking l' in water
containing less salt than that in which they were grown. Protests
by certain oyster interests called for further hearings, as a reslilt
of w.bieh Food Inspection Decision 121 (89) was issued. This de­
dsion permitted the flouting of oysters in water of lower suUnity
thul) thnt in which they would grow to maturity, if the packages
in which they were shipped were labeled" Flouted oysters."
At the time ·of the issuance of Food Inspection Decision 121 the
distt·ibution of floated oysters was not widespread and the sale was
largely in the shell, or, if shucked, by count. Later the shipment
of floated shell oysters for shucking !Lnd sale by volume presented
another aspect of the problem. If floated oysters have greater volume
thun unfloated stock from the same source, the indicntionsare that
fl"lllld will be perpetrated upon the consnmer who receives nn excess
of wuter und a de.ficiency in oyster solius. This practice of selling
floated oysters by yolume stimulated further research on the
chemistry of the process.
Early in the 1916 season experimental shipments of floated.and 1m­
floate,d oysters were made from New Jersey points to Philadelphia,
Pa., and to Baltimore, Md. Examination of the stock at destination
showed that the volume ·of the shucked ·floated oysters was about 25
per cent greater than that of the same stock that had not been floated.
Also, the floating had removed .a large part of the salt, had materiany
c1umged theflavor,and had reduced the solids content about .20 per
cent. The experiment at that timeinclicated some apparent superi­
ority in shipping und keeping quality in the floated oysters as com­
pared with the unfloated oysters. This observation is interesting in
view of tile results obtained from experiments subsequently
conducted.
In January and October, 1922, .and in the enrly fall of 1924, further
experiments were conducted. The cold season of the year was chosen
for the .first experiment, as it was believed that with the temperature
of the water low the oysters would be inactive and, consequently,
results different from those previously obtained when the floating
was carried on before the temperature of the water had fllIleD below
40° C. might be expected. The second experiment was conducted
during October, ""hen the weather was unuSllally warm, so that
as
TECIflfldAL BULLETIN
1M,
U.S. DEP'f•. OF AGRICULTURE
t,he oysters wer~ subjected to practically summer-temperatures during,
stor,age .and handling..
'
.' .
In the first expel'lment oysters from two areas .and in t4esecopd
experiment oysters from three areas were: examin,e<;l ,after remov.al
from. salt ~ater lmd after removal from bracki,sh watet:..,lit' hi~h
and low tide, following floating periods' of 42 and 46 hou.is intn.6'
first experiment,ang 36 to 42 hours in the second experiment. 'Sev~~al
sacks of oysters were used in each experiment. The .data ,(ToJJle Ip)
are the average results on each lot examined. In.Ole secondeX})el'i,
ment the salinity of the river in the vicinity of the floats,e.xpressed
as grams ,of sult pel' 100 cubic centimetel~s, ranged frolhnbout O.7aC
high tide to 0.2 at low .tide. At the same time the salinity ·of the
water over the oyster beels ranged from about 1.8 to 2.4. The un­
floated ,and floated oysters were shucked., measured, weighecl, ,and
counted. A sample from each type was wlthdl'llwn and anuly~ed.
TABLE
13.-0ltal/gcs in ousters .f/.oatcd in the shcll and retllovca at· h{.gl~ tide alltl
at
Es­
perl­
ment
Treatment
No.
.1010
Ylold
Illlr
suck
tidc
I Onln
, Count \' I
"'eight por
0 ume
,
In
.pnr
glll10n oC Indl- Solids I Bait I
volume gallon (aver- vldulIl
ngo) .oyster
--1-----------1------ - - --------Lotl:
Ullfloatcd_________________________ Galloll' Perull/ al/,ncc.•
4.116
141.70
}'Ioatod
46 hours: removed at .high
•___ 4.4014
Ildc_________________________
8.0 140.30
42 ________________________
hours: romoved at low
}'Ioutod
tldo____•
1____ _
7_4 141.03
4.423
Lot U
2: nfloatod _________________________
3.254 . __ .....
140.87
l"louted
46 hours: .romoved at 111gb
tltlo _____________________________
------- ..
_-­
Floated
42 .hours; _________________
removed at low
tide ___________•
Unlloatod from deep wnter _________•__
2..____ ~'loated: removeu tit high tldo _________
Flouted: removed at low tlde__________
'I
C.Co Per.cent Per cent
2.'iO.O
15.2
22.00
0. 5U
230.0
15.8
21.40
.52
230,0
15.8
21. 50
.4~
288.0
13.3
111.80
.71
18:00
.01
lR.80
19.40
15,03
14.98
.ao
3.645
12.0
130.80
272.0
13.9
3. ii2
:L OiS
3.S01
4.423
15.0
140,00
1:1&22
1:l5,114
135,57
200.0
238,0
213.7
180.9
14.2
23.0
43.7
15.86
J7. 70
20•.97
,
.'65
.89
•.23
EnUre sample.
Although the procedure followed was practically the same in both
experiments, the results did not agree exactly. In the firstexperi­
mont the physical eXIUDination on shucking showed the oysters of
each type to be in good condition, even though some had been frozen
during shipment. There was no indication tlmt floating, eyen to low
tide, when the temperature was very low, as in this case, had done
any serious injury nor was there anything, to indicate that unfloated
stock would not ship as well as floated stock. 'In the second e~peri­
ment, although ull the oysters were iri marketabl<;l condition, tllere
was a marked dHfcl'ence m the" physical appearance of the unfloated
and floated stock. The floated oysters taken n..t low tide had lost the
creamy color, the fil'm textul'e, and the excellent saline flavor of the
un1loated oyster und had becume pule, bleached, soft, and spongy,
with an insipid and fiat taste. The floated oysters removed at high
tide showed physical chamcteristics between these two exhemes, but
more nenrly resemblin~ the low-tide flouted oysters.
In both experiments increused yield pe,!' sack, gain in volume, 'in­
crease in size of the individual oyster,. loss of weight per gallon, a
39
BAOTERIOLOGY AND OHEMISTRY OF OYSTERS
reduced. number of oyswrsper t;nUon, and Il, loss of solids .and salt
result fJf floating were in eVld~nce.
.. .
.
In the JU'st experlment the weIght of the ID<hvldual oyswr lD­
crellsed from 0.4 to 0.8 "ram, accordinirto the tide on which it was
removed. As Il, result of the floating there was a reduction in solids
i,f lll>proxiJlllLtoly 5 percent. In the second experiment the incI'ease
In YIEl-ld produced by floating at low tide nmounted to 30 or 40 pel'
cent and ubout 111l1f this increase if the Honting was discontinued at
high tide. These. results are in contrnst with those obtained when
tltO water was below the temperature where the oyster functions
.activeiy, in which case the gain produced by floating wns only Itbout
10 per cent. From these twoexpet"iments it is apparent that the
l'hnnhrcl?pro<1uced by flouting ani gl'entJy influenced by the tcmpem­
ture of the wuter nnd. the consequent l)hysiologicnl activity of the
oysters.
An experiment eouuucted in the eurly full of 1924 included, in
ndditionto the points cO\'ercd in the previous experiments, Il study
of the chllnges which the oysters/ uoth unflollted lind flollte~2 undergo
during longer stol'llge periods 1D the shell under the inttuence of
wurt,house stonl~e at ordinary tempel'lltures und in artificially chilled
storngl~. The eirect produced iJy o~'diJlllry commercilll washing on
the volume of shucked oysters obtllllled from unfloated and floated
stoc'k wus also studied.
The plun of the experiment WIIS t.o prepllre and eXllmine 14 lots
of 3 sadnL each of lIuilonted und flouted oysters. The oysters used
were tllken from wuter huving Il salinity of ubout 1.G5 grams of
snIt pet' 100 cuiJic centimeters nnd tbey were flouted in wilter Imving
ubout 1.2 grums of suIt per 100 cubic C{~ntimctel's Ilt high tide und
nbout 0.2 grnm at low tide. The lots of oysters used were removed
from the flouts on the high t.ide or the low tide. The results of this
experiment urc given in Tuble 14..
liS .~
'l'ABLI!I
14.-il1}(:I'lIue 'w('i!lht
1,01.
No.
-~\'(1lght
'rrllUtlllOllt
por
glillull
lIel' !lflJ/on. I(izc, (/.//(1. eo 111/108 it ion
(///f[. .(!Ollllt
fllI//OII/Cft
.(/lI(t
.01
floulcll oJ/slel'1I
II~=:'
Connt
(lllr
~:,::::~~i Sulitls
Glillon Oysl\ICll
•
Sliit
Soll!l~ I~~·~r~. I~:~~;' Inc~:;e
soUds
por
~Illiutl
crollsu
III
count
crOlilio
In
INlI
\'O)UIIIO gnlloll
1 - - - - - - 1 - - ------------~- - - - ­
Unllontod..__.........
I
2 _...........do.......... "'_......
;o, ... _ _ _ ...
QU11rt.:f
1:15. H!
J~ili.:i5
a 1"JOlltO(\; hlKh li\lo..... 13·1.8:1
4 .....do............_.... J:I.~. H
220
21ft
ilia
~'O2
c. c.
17.2
17. tI
Ill. 0
18.8
20.8
JU, (i
I'rr eml Ptr .ct1ll O"nce, Prr celli 1'rr celli Prr .Ctnl
16.~:I
O. lOti
24.111 ........................
18.011
10.01
.168
.021)
2li.211 ........................
14.00
.o.'i5
)0.40
11.0
12. 6
12.11
:.~r~l~:jlg
20.0
2li,3
26.8
10. 71
.6 ..... do................. 13:1. 71
.182
7 .....do................. l:1r..24
II 1'~loulod; low lido...... 13·1.74
100
18·1
171
107
19. I
22.7
1Il.00
10.01
13.811
1:1. till
la,11
J18
IOU
21.2
22.4
H. ao
la.40
6 .....do.................
13~.
00
o .•.••do.................134. 01
..... do.................. 1:13.61
..... do..._............ .13,1.21 ..... do................. .1:l1i.1I 10.
11
12
13
..... do................. la~. ~5
14 ..... do................. 131. 02
1\).1
20.6
22. 1
m ~tA
m:~~
.Olll
22. SO }
Xl. [>8
.070
.114
.021
• (~18
.020
21. no
Xl. 81 18.12] JR. 17 17.41 .061
.1M4
111.23 18.16 Of those removed from the flouts at high tide, lots .1, and 7 were
, flOilted ':i und () hours, respectivdy, fro III low tide to high tide; lot
5 was Hoated 12 hours, Hom high tide OVer one low tide; lot 3 was
,:10
TECH:NICAL BULLE'l:IN 64, U. S. DEPT, OF AGRICULTURE
floated, 18 hours, to two high tides; and lot 6 was floated 42 hours,
Irom low tide over two tides. Of those removed at low tide, lot
9 was floated '{ hours, from high tide to low tide; lots 8 and 1.3
were floated 13 and 11 hours, from low tide to low tide; lot 10 was
floated 24 hours, fl'om low tide over one low tide; lot 11 was floated
37 hours, !rom low tide over two tides; and lots 12 and 14 were floated
48 hours, Irom low tide over IOUI' low tides.
'Within 40 hour.s after removal Irom the water, two sacks ol each
lot w.ere .shuc~ed and examineq, the third s~ck being res.erved. for
exanunatlOn lifter a storage penod. At the tune ol shuclnng vIsllal
inspection showed that both the unfloated and floated oyst!ers were
in excellent marketable condition, although there was no difficulty
in distinguishing the floated from the unfloated stock, owing to the
pale, bleached, and bloated appearance of the former, especially of
those removed Irom the floats at low tide. The floated oysters ap­
}leured lurger than the unHoated oysters; contained much Iree liquor
~n the sheil, und emitted large quuntIties of milky liquor when
pierced.
Each lo.t ol oysters was washed as described in Table 15. Belore
and ulter washing the oysters were measured llnd after waRhing
tfl'ley were also weighed, counted, and analyzed for solids and salt.
Quantities of each lot were shipped in ice to Buffalo, N. Y., where
they were re-ieed anel returned to Baltimore, Md., to be examined
lor free liquor.
'.rABL~J lu.-OlwIIY('.~
r~ol
Trealment flf sholl
No.
oystcr~
I
in volume llrodUcca llY commercial
(/.II(t ftou/ed oysieTs
wa,ql~inu
'j'reatlllont, of shuckod oystors
{HiOwn for 2 minutes with liO gallons of waler••••..•••••••
I t, I
U 11 I 011 el . ••••••. Wushod in tub for 2 miuutc.q with fresh wllter; ngltn!or!...
of IIn{loated
Gain in
volume
'L(l"'~
Per unt.
Pcr CCTlt
ill
voiume
5." ......... . i.7 ••..•.••••
i.4 ..••••••••
.0
0..0
Iio...... __ ..... _ 1110\\,11 for 2 minutes with no gallons of wnter ..............
romoved Wnsi",d In tub for 2 minutes with fresh water; IIgitnted ••.
nl high tilio.
4 ••••• do ••••••••••••• .Blown for 2 minutes with liO gallons of wlitor •••.••.•••... ••••.•••••
4.1
5 ••••• r.Io............. WII~I,"d ill tub for 2 minutes.............................
4.5 •.••..••••
(I ••••• tlo••••••••••.•. Wllshe" in tub for 2 lIljnlltc.~ with fresh wlIt.er••..••.•••.
.0
.0
7 ..... <10.•.•..• _•.•• Iliown for 2minules with liO glillons of willor.............
.0
.0
8 1'10Ilto<l; romoved _•••• <10•••••••••••••• _••••• _. __._••__••••_•••••••••••••_...
2. 0 ......_•..
lIllow tido.
II ..__ .tlu............. "rllshed in t.ub for 2 minutes with fresh wnler •.•• __......
.0
.0 ill ••••• tlo......._._... mowu for 2 minutes with 50 gallous of watm· ••••_........ .....•••••
1.9 2 •••.
3
J·~iQntod;
i~ =::::~~::::::::::::: .~~·:~~I;~I~.i~~.t~:~!~':.~.'~:j~~~~~.~'~~~.f:~:~:~~~~~~::::::::::::I
13 __•••do............. lliown for 2 minutes with 50 gnllons of wnter __...........
14 ._...
do...................._............................._.
uo..................
3: g.. ······:rl
.0
.0
.0 .0 The changes in volume produc('cl by the washing process nre given
in Table :W. The average figures obtained on the weight, count,
yol lillie, solids content, and salt content of the un floated and floated
. oysters are given in Table 13, which shows also the average per­
centage changes in volume, count, and solids conte::t. The l'emark~
able feature brought out .by this experiment is that the length of
time offlonting bad practically no bearing on the changes produced,
the det('rmillin'g Iactor being whether the process was terminated
during a low tide Or a high tide. The oysters floated for seven hours
and removed at low tide showed almost iflentically the same gain in
volume and chunge in composition as those floated for 48 hours and
BAOTERIOLOGY AND CHEMISTRY OF OYSTERS
41'
removed at low tide. The same condition was noted in the oysters
I'emoved from the floats at high tide.
The free liquor drained off the unfloated oysters returned· from
Buffalo ranged from 3.7 to 2.1 pel' cent, an averaO'e of 2.6 pel' cent;
that of the floilted oysters removed at high tide E.'om 8:9 to 4,,7 per
cent, an Ilverageof 7 pel' cent; and that of the floated oysters removed
at low tide from 14.4 to 6.8' pel' cent, an average of 9.9 per cent.
These. fi.gures ~ndicate t1~at oystel:s floated !l~ low tide developed large
qU!intItIes of lIquor durmg translt-quantltIes larger than those nor~,
mally present in properly washed and skimmed oysters after ship~
ment. . .
.
' ,I'·
The residual sacks of oysters were stored first for 10 days at a
tempel'atui'c of about 30° F. At theexpiratiol1 of this period one-'
half of the oysters in each sack were opened and examined visu~lli
and the other half stored for 6 to 10 days longer in an ordinal'Y
shucking room exposed to prevailing temperatures. At tl1eend of'
both periods the oysters were living nnd in marketable condition;"
There was still a difference between the unfloated and flouted stock,'
but both showed evidence of dl'yinO' about. the gills. After washing,
both types of oysters presented a fair appearance and were, in fact;
marketed commerciully, in spite of the fnct that they had been out
of the water for 20 dnys, half of the time exposed to wnrm weather.
This does not indicnte thnt floating is necessary in order to produce
an oyster which will stand any reasonnble shipment or stol'l1ge in ,the,
~~.
,
These experiments show thnt the duration of the floating period·
has little effect on oysters, that tloating is not necessary to produce,
oysters which will stand shipment well, and that floating in f1'e9h
water materia-lly changes the composition of oysters, especially if the
floating period is terminated at low tide.
..
As a result of this experimental work, Food Inspection Decision
211, Adulteration of oysters (90), was issued in Jtme, 1927. This
decision revokes Food Inspection DecisiOIi 121 (89) and reaffirms
Food Inspection Decision 110 (88). The shil?n:ient of floated oystel's;'
even if labeled "li'loated oysters," now constItutes a violation bf tIie'
Fedel'al food and chugs nct.
' .
SHUCKING-HOUSE SA.NITA.TION
,• ~
Clean oysters, improperly handled, i;n an unclean and insanitary
shucking h011se, mny become so contaminated that when shippe~
they are unfitfol' use. Fedel'ulan~l. State authorities .? 0 what c~n"
be done to regulate and conhoI condItions upon the groWll1g grounds,
but the responsibility for sanitary conditions in the shucking house
rests squnrely upon the dealer or shipper. Federal and State in- '
spectors may assist the shipper by calling attention to conditions
open to improvement from the sanitary standpoint. Such inspec­
tIOns, made in .coop~ration. with t~e shipper l:a~l1Cr than ~ith any
idea of hampermg hIm or mterfermg wl~h legltlmate practices, cal!
be made only occnsionally. Th~re£ore, it is the d.ealer himself ~ho
must assume the burden of keepmg a clean house m order todehyer
a clean product.
Phelps (71) states that the qua~ity of oysters dependS upon. (1.)-;
the character of the water from wl11ch they are taken, (2) the process
r:("",'" ,
"
";
";'
42.TECH]fICAt ~tJLLETIN ~, ,tr. S • .DEPt.OFAGRlOut,.TURE
of ,handling from ,the ,shucker t~;the shipping package, and :(3) "the
treatment which they receive from this point to theponsUlller. ,
In 1911 Stiles. (8IB) directed attention to :the importance of ~~ni­
tation within the shucking house. He stated tha~w,lthout the 'devict;ls:
necessary f~r cleansing Il;nd stedl.izing it is imp.oss;ible..to prepare.t1;le,
&0;1 shIppmg package lD;a samtary manner.. Speclficsuggeshons
for the :maintenance of sanitary conditions within "the' shuqking,
house were made by Round in:916 (76).
,
Beginning with the premises outside the shucking house proper.,
it .is suggested that orderliness and neatness be maintained. It till
understood that the ordinary practices of the industry make it neces­
sary to ,have s:b.ell J;liles, s,tocks of reserve materials, etc., on the
premises. No objectIon can be made to such accumulations. Dirt, :
piles of decomposing materials, pools of stagnant water, and other,
similar ,nuisances should ,not be tolerated, however. A neat and
orderly outside appearance has its.effectupon visitors and passers-by,
as well as a direct bearing upon the cleanliness of the pl1oduct:
shipped.
;
For several reasons it is advisable to use whitewash and;paint
libel'lilly with.in the shucking house. Painting or whitewashing
should be done at IeJlst once a year" and more often if necessary.,
The walls and the ceilin~ must freed from dirt and cobwebs ,before
they are painted or whItewashed. Paint an,d whitewash ,aregermi-.
cides and their use also gives better light and a' better· appearance.
Thus paint and whitewash hnve a direct effect on the quality of ,the
shucked oysters and an indirect effect, through ,the impressions made
upon the employees that they are working ina clean shop and must
be clean themselves.
"If possible, the floors and benches should be .made of concrete in­
stead of wood. Concrete can be keptcleQ.nmore easily. When bins:
and benches are emptied they should be cleaned from ,allaccumula­
tions of mud, dirt,and seaweeds. This can be done .by hosing
thoroughly, or, if sufficient water pressure is lacking, by scrubbing
with brooms and rinsing with plenty of water. The floors should be
washed daily in the same manner.
Particular care is necessary to provide and use absolutely clean.
utensils. Cans, colanders, knives, skimmers, and tanks should be
cleaned and rinsed whenever empty or not in use. A liberal use of
steam for cleaning and sterilizing them is necessary. Sufficient steam
for this purpose should bepl'ovided, regardless of the temperate
weather of fall and spring, which does not call for steam for heating
purposes. The steam may be used as live steam or under pressure.
If steam can not be J;lrovided,a solution of calcium hypochlorite may
be used as a cleansmg and sterilizing agent. The routine use of
hypochlorite solutions for rinsing bins and benct;3s is to be recom­
mended because of its sterilizing and deodoriziug properties.
Convenient toilets for employees should be provided. These toilets
should have runn~g water an~ they must, be used carefully. Em­
ployees should be Impressed With the fact that they are handling
foods that may be eaten raw. Therefore, they must always wash
their' hands after using the toilet.
Doors and windows of the shucking house should be screened
tightly to prevent the entrance of flies and other insects.
be
~tC"';'::"(:';
.
; , 'BACTEltIOLOGYAND ' CHEMISTRY OF . 'OYSTERS
43
: :~li.ch ~ns, beenw,ritten -regarding compulsory ~~riodic phYElical
e~amrnahons
ofAll food .handlers, such as cooks, walters, and oyster
l'inllckers.. A.s appli~d to oyster shuckers s~ch a regUlation wo.uld ;be,
of'value ,If It ehmrnated 'from the' .shucking: house a11carrlers of
B.adllus typh08U8 ,and .all sufferers from. venereal or .other c?nta~ious
dIseases. In the absence of such a reqmrementthe dealer or shIpper
is'linder an obligation to inquire carefully about the health of each
employee and about any' past case of typhOid fever or other contagioUS'
disease. It is also important that the supervisor in the shucking
house be advised of any illness in the family of each employee.
Tp~re is always danger that disease-producingorgllnisms may .be
f1rapsmittedfl'om llOmes where illness prevails by persons 'WJ:lO llI;e Dot
themselves suffering from the disease~ From the kllowledgegaineli,
regarding the .health of each employee und his family the employer
should draw conclusions and act ,accm·dingly. Bearmg in mind that
oysters offer a favorable medium for the development of .bacteria, and
ar~ frequently eaten raw, the employer should rigidly exclude :from
work in the shucking house all persons. suffering from contagious,
disease .01' .known tp be harboring organisms of disease although not
suffering .themselves.
Personal cleanliness, of course, must be insisted upon. 'l'ha habits
and person of the shucker should be clean. The shucker's hands must
be kept as clean as possible in order not to unduly contaminate .the
shucked oysters with mud and debris in the process of opening. In
s'piteof nll precautions, it is possible that some unhealthy person or
some one carrying disease organisms may be employed. Employees
should be impressed with the idea that they are working in .11 kitchen
where food is prepared..
WASHING OYSTERS
IN THE SHELL
Where oysters are grown on muddy or soft bottoms t.he shells may
become coaled with mud. Unless removed before shucking, this
serves to contaminate seriously the shucked product.
Where power dredges are used and deck space is available, much
of the mud" if soft and not sticky, may be removed when the oysters
are first taJten from the water. This may be done by rinsing them
several times in the sea water while still in the dredge and just before
dumping on the deck. When dumped on the deck the oysters may
be washed with pailfuls of w.ater taken from alongside the boat.
When tho oysters are taken by means of tongs by men working in
small rowboats this washing is not so easily done. Furthermore, if
the bottom soil is claylike and sticky it is removed from the shells
with difficulty, even when wet, and, if allowed to dry, such shells
can be cleaned only by scrubbing.
Under the present system of handling .at the shucking house no
method is provided for cleansing-the shells before shuckin~. 'Yhether
serious attempts to develop such a method have been made by oyster
growers is unknown, but the literature apparently contains no ref­
erences to it.
It is often stated that it is impracticable to' attempt to rid the
~~terior of the oysters of mud at the shucking house, but the impor­
c
44
TECHNICAL ;BULLETIN 64:, U. S. DEPT. OF AGRICULTURE
tance of this mud ns a factor in the contamination ,of the shllclred
stock would seem to warrnnt some expense and inconvenience on the
part 0:1; the shipper in an attempt to eliminate it. .Although it ,might
be clifficult to :put sllch an operation into effect in some of the smaller,
poorly equipped shucking establishments, the installation of suitable
D.'ppal'lltlls would not seem too cliflicult or expensive for the larger
companies. The importance of this contnminatin~ factor where
muddy oysters are lumdled can not be overemphasized.
OUT OF THE SHELL
Shucking is always followed by washing. The efficiency of the
)'ritious ~et1lOds of wush~g in ren,lovin[; b~cteria. fro.m the shucked
oysters lias been the subJect of extenslve mvesbgatlOns. In 1904
Houston (46) established by experiment the fundamental principle
that oysters polluted on the growing areas can not be wnshed' free
from Baeillu8 coli. By none of the present commercial methods of
washing can the original Bac-illu8 coZi score be reduced. The efficiency
of a waslii.ng method is measured by the extent to which it removes
t11e dirt nnd thebncter,itt introduced during the shucking operations.
'fhe bacterial content of the oysters frequently increases grently, ow­
ing to the introduction of mud nnd other foreign ml1terini during
shucking. Hibernnting oysters nnd oysters from sewnge-free wnter:;
scoring as low ns 5 often score 500 after shucking. In 1916 nnd 1917,
Pttrsons nnd Fnrrur l'eported the results of their experinlents upon
the efficiency of various methods of washing ns affecting the bacterinl
content of oysters. The dntll in Table 16 show the e'ffect of the
8hucking and washing processes upon the bneterini content of
oysters.
T"\UI.E
lG.-Effect on .~corc of slwcldnU
II nd
of diffcl'I?'1I t mct hods Of 1ouslLi1l0'
Score
Condition of
oysters
Method of wnshing
Before
Before
shncklng washing
-------1--------­
no '!llg on skimmer with
tnp Wilier •••••••••__•____ ••. I1lbcrnnting••___ .•
Uo•••••• __•• , .................. _••__••• __•.•••• _.•• _•• 110 ••• _.,., ••• _
Holding
In tuh o(
Wnler:
, .1.1
... ,...frcllh
_______
•___ •_____________________.. ___ ..
____________
nlinu1os~
~
30 milltucs. -.-••--.--••••- ••.• -.-.--•••-- ••••••.•
_(lo~
'r':: :~l~:::::::::::::
~ . . . <-
:aJ minutes
.--••• -.--.-.--.- ••••••••••- •• -.------.]
do...._____ _____ _
._.. do •.•• _•• _. __••
clo
'
::::rlo::::::::::::: .
•• _.do._._ ••_••. _••
30 minutes ••.•••___ ._•• _____._•• _•••••. _......._•••••• 110••_._••_•._._ :::::~~::~:~~~~~::~~~~:~~~~~~~~~~~~~~~:~~~:~::: t~~j~~~~~~~~~~~~~~
20 minutes. _•• _••• _____. __•• __ •• _·._.~
Arter
washing
!l~~~I~~.~r~~~~~::::
•• _·· ____.•I' .... do •• _••__•• __._
Iiosing hefore nnd nfter immcrsicn in tubs.__••___••..
Do_•.__ •••_••••__••••• __._._ ' __ ' __"'_' ._. _______•
••••do.__••••• _••••
•••• do•••••• _._._••
('l
('l
I Complied (rom dlltn submitted by P. B. Parsons in 191;.
'Not gl\'en.
l/rhere were Cew oysters OD the skimmer. 1'IenLy oC waler was used.
(')
(')
500
14
4
14
2
2
50
-il
(')
('J
230
320
410
rJOO
o
50
32
2
4
41
23
32
50
o
o
2
5
41
32
410
140
230
4
6
500
(')
(')
(')
(')
(')
500
,23
4
500
320
50
500
140
41
32
140
41
.'JO
50
500
500
410
410
4,100
5
50
500
'4
500
45
. ,:lIA.Q:r:&R~O:J.i,QGY .AND· OHEMISTRY OF OYSTERS ,
TABLE 16.-EtTect on score of shucking and of .det(erent .ffl(Jthods of WUBhif!g-­
Continued
Scorll
Method 01 washing'
Oondltlon 01
oysters
In blower:
AK\ltitcd
7 ,mlnule.<
,'_______________________________________ nlbernatlng______ _
millutes , __________________________________________do____________ _
3 minutes t ___________________________________________ do____________ _
6 minmes t_.__________________________________________ do ____________ _
limlnules , ____________________________________________do____________ _
7 minutes ,____________________________________________do___________ _
5mlnules ,____________________________________________do ____________
3 minules , ___________________________..________-- _____do _____________
liminules t ____________________________________________ do_____________
3 mlnule.q t ___________________________________ .:________ do____________ _
3 minutes , __________________________________..________tIo ____________ _
Ii mlnules , __________________________________..________do____________ _
10 minutes ,___________________________• _______________do____________ _
10 minutes , ___________________________________________do_____________ Ii minutes , ____________________________________________do_____________
7 minutes ,____________________________________________do ____________ _
Ii mlnllte.< ,_______________________________________ Nonhlbernntlng__ _
'6 minules ,______________..____________________________do____________ _
30 minute.. , _______________________________________..__ do____________ _
10 minutes , ___________________________________________do_____________
30 minutes , ___________________________________ . ____ .do___________ _
Washed
In running
water under tap lor ao mlnutes________do_____________
Do___..__
..____________________________________._
___._do.____________
O~
, Fresh water was used In the blower.
I
Alter
Defore .Delore
shucking washing washing
6
6
5
14
14
o
o
o
o
a
o
2
3
2
4
3
~2
320
HO
230
140
23
14
14
14
14
14
230 32
320
320
14
32
50
14
6
"
1
o
Q
Q
l~
3
3
14
41
320
Ii
41
320
320
320
1,400
1,400
2,300
230
320
410
410
23
320
600
410
60
230
~I
230
• Snit water was used in lhe blower.
In many houses it is customary to wash the shucked oysters im­
mediately after shucking on a perforated skirruner with running
water from a hose. Such washing has little effect on the bacterial
content. It is usually superficial. The oysters on the skimmer are
so numerous that the agitation of the mass by the force of the water
and py stirring with the hand or a paddle is lIlsufficient to expose the
entire surface of each oyster to the stream of running water. Many
b,acteria adhering to the mucus of the body and to the gills escape
the action of the water Ilnd are carried on to the finished product.
After ordinary hosing on a skimmer, the scores were the same as
before washin·g. If It few oysters spreacl out on the skimmer are
treated with plenty of water, under strong pressure, it is possible td
effect a slight reduction in the score. Under commercial conditions
this would gecatly retard operations. As orclinarily practiced, hosin~
of oysters on a skimmer can not be held to be nn efficient means or
washing.
By another method of washing, shucked oysters are held in tubs
or tllnks of il'esh or saJt water nDel are occasionally stirred with a
paddle. The, results of ~xpeI~mcnts to demonstrate th~ effect on the
SGore of holdmg oysters III tubs of fresh water for varymg lengths of
time are given in Table 16. The oysters, collectecl during the hiber­
nating season, had Jow scores bllfore shucking. As a result of con­
tamination during shucking the scores were greatly increased. Hold­
inO' the oysters in tubs for as lon¥ as 30 minutes did not remove the
ba~teria lDtroduced during shUCKing and thus did .not reduce the
scores to those originally found .. No differences in results were ob­
tained when salt wllter was used m plnce of fresh water. Dllta sub­
mitted by Parsons and Farrar show that, owing to the use of dirty
46
~Eo:a;NrCAL BULrlETflifM, !U. ;s. :i>.EP1';
'6F ',i\ainoUi.TUBE
water,'the score may'he increo.s~a dur~g the w'eshing proc~ss. Wlien'
care WllS taken to use clean water for each batch of oysters and to
stir-the mixture freqllently some sUght reduction in score was effected:
The indications that stirring had much effect in reducing the score
were too meager to be o:f very great significance.:nnd subsequent work
indicated that stirring has little effect on the efficiency of this process.
Further e~.p eriments showed that washing in tubs of fresh water
polluted oysters tuken during the actively feeding sellso~ do,~s
Dot I'educe the score. (Table 16.) Polluted oysters washed m'thls
maImer' still had scores as high as those' not washed. These results
indicate thllt it is impossible to remove Baeill~t8 colifrom the bO,dy
of polluted oysters by wasbint>'.
. .
Experiments condllcted to ,determine the effect of hosing -oysters
before and after jmnH~I'sion in tubs of water (Table 16) showed that
such hosing adds nothing to the efficiency of the . washing prol;!ess.
Some of the results support the statement (p. 45)thilt tl few oyst!,\rs
spI'end on the skimmer und trea.ted with plenty of water can.be
reduced i,n bacterial content.
. ;.
"rhe invest.iga:th~s conducted byPttl'sons indicated thut the m9st
practicn'! and emcient method of washing oyaters to I'educe ,the
contami?atioll introduced by shucki;ng is the use of the blo:ver. .The
blower 1S a metal tank ,eqUlll>ped WIth u perforated plate Just above
the bottom. ,Air is forced up through the perforntions in this plate
into the mixtlU'e of water ancloysters. By the force of the air the
oystersnre tossed, about and agitated violently, thus exposing;~he
eptire body to the washing action of the watel' or brine. Dirt, ,pieces
of; shell, and slime, sinking to thl! bottom of the tank, are collected
ioll ~ the space between the bottom and tbe perforated plate. .''{his
accumulation of waste must be I'emoved after each operation aitd
dean water mQ.st be used for 'each blo,vin cr. Otherwise th!'!' .m~fuihil:
gp,thered in the bottom ()~ ~he. tanl\ is re~sh:jbllted throQ.gqout 'We
)':\1s11 water and the efrect 1S to ~ur~e!, c~ntaIhmate the oyster$ ;l'a:tlie~
ilill,nto cleanse them. The mam obJectIOn to the use of the blowet:
that J?I:olonged blowing may bloat the oysters and thlls adulterate'
them wlth water (p. 47). l'he use of a weak salt solution will
e,Iiin:inate this trouble. .
. '.
The results of experlments on clean oysters collected durmg the
~iherll!ttiIl~ seaSon and on polluted Qysterscollected during th~'~c-,
tively feedlllg season (Table 16) show that by use of the blower
the score of shucked oysters can be reduced to that of the oysters
before shucking. No recillction in the score of the pollutedoyst~rs
below. that of the original shell stock could be mll.de, ho'wever.
Occasional hosing of the oysters before blowing was .resorted to;
but with little effect on the bacterial c<>!ltent. It was found that for
cleansing purposes, there wa~ no. difference between the use of?resh
water and the use of weak brme m the blowf'l'. .Also as good results
were obtained by blowiI?g for from :three to five minutes as '~y
blowing for a longer perIOd.
Of all the present commercial methods' of washing studied the
use of the blower wa,s the only one that was e'fIicient in redu~ing
the bacterial content of the shucked oysters.
. ,,'
Anot~er experim~nt (Table 16) was conduct~d to learp .the effe~t
of washmg oysters ill tubs or bllcke~ under rapIdly runDIng streams
is
,,'
·BAOTERIOLOGY AND OltEMlSTBY 'OF OYSTEBS
47<
of water for prolonged periods. Nonhibernating oysters were sub­
jected to this treatment. The I'esults were negativ.e ill so far as they
show any e1fect upon the score. Such.a Wqshing process will not
.I·educe the scorel:>elow that of the oysters before washing.
To sum up the present knowledge of the bacteriology involved in
the washing process, -hosing or spraying the oysters WIth water on Ii,
skimmer will not reduce the bacterial contamination due to shucking
anel handling, but washing in a blow~r in a weak brine for froni
three to five minutes will reduce the bacterial content to about that
of the oysters before shucking, without undue bloating. No known
method of wllShin~ willl'emove fEom the body of the oyster ~vidence
of pollution gainea during gL'owthon the beds.
EFFECT ON VOLUME AND COMPOSITION
The composition of shucked oysters can be greatly changed by
pl'olonged washing in fresh water. If the ,process is prolonged un­
duly the oysters become adultemted within the meaning of the
Fedcml food Ilnd drugs act. So much fresh water is absorbed by tlle
oysters that bloating or "fattening" takes place and fraud is per­
petrntcd on buyers of such oysters. Furthm'more, valuable soluble
solids nre lost in the wash water or liquor that is drained off anq.,
discllrded. Although any fresh-water wnshing must result in some
loss of soluble solids, as wellns in the addition of water, a reasonable
washing of shucked oysters is nf1cossal"Y to obtnina product free from
shell, dirt, Imd 'foreign nll1teril1l. The process must be regulnted to
a degree that will pormit a thoro\.lgh cleansing without soaking and
adulterating.
Realizing the possibilities for illegitimate gain to dealers from"
the incl'euse in volume due to soaking, and recognizing also the prob­
ability of adulteration dm'in a the washing process due to the ship­
pers' lnck of knowledge of tile chemical changes taking plnce, the
Bureau of Chemistry studied the efrects produced by vaTious methods
of washing oysters.
During the season of 1916-17 oyster-washing. expet'iments were
conducted near Pl'ovidmlce, U. I., New Haven, Conn., New York,
N. Y., aud the Chesapeuke Bay (Md.) section (repOl·ted by E.J.
Shanley). The washing process employed in the establIshment
under investiglttion was not~d nud the. expm-iments were planned to
simuillte such processes. The volume of oysters was measured before
und after wnshing~ Iwd the chunge .of volume under the conditions
was noted, Samples ofoyoters for analyses were collected before­
and after washing. 'fhe procedures followed in these experiments
are briefly described and the results obtained are given in Table 17."
Data on the solids and salt content of the meat and liquor of the
samples, before and after washing, also were obtained. Only the
determinations on the entire samples are given inilie table.
t
TABLE
.~
l7.-Summary of results of oyster-washing experiments conducted at New Haven, Conn., and Providence, R. I., 1916-17
Whole sample
Meat
Locnlily and cxpcri.
llleot No..
Change from
washing
Liquor
Method ot washing Solids
Un·
Un· Washed
w"shed Washed washed
Salt
Un- Washed
w~~-edlwaShed washed
Ollln
in vol­
ume
Solids
Salt
--- --- ---I - --- --- --- --- --- ---
New1_____________________
llaven, Conn.: Ptr Clnt PiT cenl
cent Ptr <tntI Per cenl
Sprayed with hose 1 minute; stood In tub ot water 1 hour__ 86.48 \l2. 57 PiT
13. 52
7. 43
Ii. 86
Oreeuport, N. Y.: ____________ .. ______
3A ,__________________ Washed in hlower 3 minutes; sprayed on skimmer 1mlnute_ 85.40 94.70
14.60
5.30
17.20
In fresh water 3 minutes; washed with running water_
3D , __________________ Dlown
98.50
12. 07
1. 50
21.06
Diown in tresh water 3 minutes ___________________________ 87.93
11.30 ________ 20.97 88. 70
Narragllnselt
Day, R.1.: 4_____________________
Diown tor 5 minutes, with stream ot fresh water running 85.60 89.60
14. 40
10.40
20. 40
continuously tbrough blower.
5_____________________
Washed on skimmer M minute; stood In tank ot water,
sa.
30 86.10 16. 70
13.
90
20.
61
with occasional stirring, 20 minutes.
6_____________________
Sprayed on skimmer 1 minute; blown in (resh water 6 86.70
95.90
4. 10
21. 58
13.30
minutes.
7__________________---
Passed along rime board over which water constantly
81.10
87. SO
18. 90
12. 20
18. 46
flowed •.
7A___________________
Oysters trom experiment 7 collected in tank and agitated
81.10
90.90
18.
90
9.10
18. 46
wlthstream ot tresh water until tank o\'crflowed; wash.
8_________ • ___________
Ing continued 15 or 20 minutes.
Dlown in Cresh water 3 minutes ___________________________ 8A ___________________ -- ___do.____________________________________________________
22. 82 8D ___________________
Dlown.lu l.il per cent brine 3 minutes _____________________ -------- -------- -------- -------- 22.82
22.82
New9 _____________________
lla\'en, Conn.: Dlown In tank through which Cresh water constantly 8i.86
94. 17
12. 14
5. sa
16.16
flowed 5 minutes. Narragansett
Day, It. I.:
10____________________
11____________________ Dlown In Cresh water 3 minutes ___________________________
19.97
Sprayed on skimmer 1 minute; stood in weak brine 2 min- --iiO~ro- -------- ---ii~ro- -------- 21.50
utes; stirred a few times; some brine poured 01I; oysters again stood 5 minutes. 2~~
I
Slight loss. 'None.
Ptr <tnl Ptr cent Ptrctnl Ptr cenl Ptr etnl Percent
14.41
1.05
0.56 -19.31 -46. 6
(I>
15.39
17.50
18. 77
.48 -10.52
.30 -16.90
1.12
.87
.80
.28 -10.49
-57.1
-65. 5
-65. 0
(I>
15
4
t;a
o
~
....
~
tzt
~
~
17.51
1.02
.28 -14. 17
-72. 5
9
18. 26
1.02
.47 -11.40
-53.9
2.5
,,~
20.30
1.03
.35
-6.93
-66.0
12. 5
17.34
1.13
.54
;:t
-6.07
-52.2
17.31
1.13
.31
-6.23
-72.6
7.5
16. 92
18.48
20.01
.82
.82
.82
.29 -25.85
.35 -19.02
.06 -8. 36
-64.6
-57.3
-19.5
0.2
8.0
13.01
1.02 .37 -19.44
-63.7
(I)
(I> 6.0
rn
~
I'd
!-2
~
Ii­
14. 14
19.80
• 2 lots of oysters used.
1.04
.82
.42 -29.19
.32 -7.90
-59.6
-60.9
8.0
1.8
~
8
~
~
,-,.1'1
,
•
•
BAOTERIOLoGY AND O:lIEMISTRY OF O'YSTERS
49,
:a8
.A.:lthough the 11 experim ents described can not be consideredled.,
control
accura te scientifically, in that all the factors were not salt
caused
they show the increases in volume and losses of solids and
and
by variou s washin g methods. The results indicat e that (1) salt
;(2)
g
washin
of
form
any
by
oysters
the
solids are extract ed from
wIth
when oysters are washed with fresh or salt water .in tubs, or when
(3)
and
little;
very
es
increas
volume
salt water in a blower, the
. It
washed with fresh water in a blower the volume increases greatly
to
carried
if
g,
washin
of
method
blower
or
is eviden t that the tub
er,'
excess, will cause adulter ation. If proper ly controlled, howev
none of these method s of washin g need cause serious adulter ation
with added wate,·.
As the water conten t of oysters varies somew hat with the region
g are
in which they are grown and as different methods of washin
con­
those
to
similar
ents
experim
es,
practic ed in different localiti
the
in
and
Yode
New
in
out
carried
were
d
Englan
New
in
ducted
York,
New
near
s
shment
establi
nine
At
vicinity of Chesapettke Bay.
com­
in eight of which a blower was llsed, experim ents under strictly
Bay.
ss
Prince
from
oysters
with
ted
merda l conditions were conduc
were
and
er
skimm
a
on
minute
1
about
for
d
spraye
were
The oysters
then blown for period s varyin g from .5 to 10 minutes.
per
The maxim um loss of solids in anyon e experim ent was 18.8
of
loss
e
averag
The
cent.
per
4.5
cent and the ulinim um loss was
gain
um
maxim
The
cent.
per
11.8
was
lents
experin
nine
the
solids in
in volume was 18 per cent and the minim um 4.2 per cent, or aninaver­
the
age gain of 8.2 percel 1t. The salt was largely removed
washin g process.
Of other experim ents conducted neal' New York one indicat ed that
is
when 1 per cent salt solution is used in a blower the loss of .solids d
obtaine
that
th
one-fif
about
volume
in
gain
the
and
ird
about one-th
ratio of
when fresh water is used. Anoth er showed that when thevolume
is
in
gain
the
ed
increas
is
blower
the
in
oysters to water
greatly decreased.
In the Chesapeake Bay region the methods of shucki ng .and wash­
e in
ing differed greatly from those farther .north. It is the practic
which
s
bucket
into
oysters
the
shuck
to
ry
indust
ic
the south Atlant
are one-th ird to one-ha lf full of fresh water. After being passed
tubs
over a skimmer the shucke d oysters are collected in large
ptutinl ly .filled with fresh water. The collection of shucke d oysters
have accumulated.
ill these tubs is continu ed nntil 30 to 50 gallons
ies
This means that some of the oysters are soaked in varyin g quantit
hours.
four
to
two
to
up
s
of fresh water for period
­
In order to investi gate the effect of such a process on the compo
process
g
washin
the
after
and
before
d
obtaine
sition, samples were
from a numbe r of shucki ng houses. The loss in solids during wash­
gain
ing was determ ined, but no figures are available to show the
the
in volume, if any. The effect of this method of washin gofonsolids
tages
percen
the
and
oysters
the
of
t
solids and salt conten
Imd salt presen t in unwash ed oysters from the Chesapeake Bay
I'egion are giYl'n in Table 18.
789:;5 °-28--4
SOt-
"
TECRNJ.CAL BULLETIN 64, U. S. ~EPT. OF AGRICULTURE
Loc8lIty
Method of washing
) Solids
Loss In •
BaIt
.solids
--:,"""- - : - - - - - - - - - - - 1 - - - - - - - - - 1 - - - - - - - - 1 . ' g'le'r So:und , •
rUnwllShed ___•_____________•
TIW .
. -._.------------------------ \ Washed
T!UI~ier So~nd. IWd Potomuc IUver , _______ {UnWll3hcd:~::~::~::==:=:===
Wnshed____________ •_______ _
JUllwlIShed - ----.-----------­
PtitOIlUIC River '---------------------------1~T.'::~ke.:~iiii\;nie;iiDd-rin;jcd
•
•
{Unwashed _________________ _
. ,
Shucked in water IWd
PoCdmoke pllWts -----.------------------- Wdrained.
IIShed ____________________ _
,
{Unwashcd _____ •___________ _
'Flshing Bay '"_____________________________ Shucked in wuter ________.__ _
.
WllShed____________________ _
Per ant
20. 8
Per cent' Pt:r' crnt
17.9
17.4
13.7
17.7
15. 8
17.8
21.
4
.0.•34
. 14
• 58
:ll
. 29
.15
.15
• 37
________
. la 9
_.__ ~ __ !~ __,
21.3.
____"•• __ ~
10.8
0.5_
_________
20.1
.14
20.3
18. 7
17.8
16.0
.21 ______•'5.1
.43
___
• III
• 4. 8
1'13
14.4
~.
.6.0
,'Unwashed oysters shuoked ill to dry containers. Licluor WllS drawn off beCoro sampling.
. ,
"Washed oysters shuckod into contuillers coutulnlng wllter, thon collected In tubs of water'lWd soaked
.for ~urlollS lengths of time, d"JlCllding on factory practice, or probably not longer than ~ or a ho~rs •
.As it had been ohserved that unwashed oysters "bled" or excreted
liquor more freely than washed oysters, experiments were con-:
ducted to study this more extensively. Tlu\ results ·of these experi­
ments,based on washings in bibs and blowers, ·confirmed the conclu­
sion that unwashed oysters "bleed" profusely ascompareCl with
washed. stock. FUl,thermore, when the original liquor w.asdrawnoif
and discarded the unwashed oysters continued to "bleed" arld were
floon suri'ounded with more liquor. This" bleeding" was stopped by
immersing the oysters in fresh wuter.
'
This observation led to a laboratory experiment to determine how
long af!e.r. shucking" bleed in~" would continue and to ascert~m. 'tl;le
compOSItIon .ofthe excre~ed l1qu?r. The more torn the .oyste~ m.e~t,
the greater 1S the excretIOn of liquor. Therefore, careless opemng,
which cuts and tears the meat,tends to increase the quantity of liqiior
that win separate on shucking. The experiment consisted m(l) sep~
arllting the liquor within the shell, (2) separating the liauor 'ex­
creted during the shucking, (3) separating the liquor that Ilccublu­
lated when the shucked oysters were .allowed to stand for 30 minutes,
and (4:) separating the residual liquor produced during the 20 hours
ioU,Qwing shucking,oYer and abovethllt which had been removed
within tlie first· 30 minutes uftershucking. The quantity ,and compo­
sition of these separated fractions are given in Table 19.
1oitMn. the o'II8ter 81icll a-n~
that cllIerctecl d.ul·inu and, ,after 81wwlcinu
TABLE 19.-Qllflntitu alld COt1l1)osil ion Of liquor
Liquor
Propor­
tion 01
totlll
, contents
Solid
matter
Ash
Salt
fit
Protein
(NXO.25)
--------------1------------"·-' --In sbell _____________________________________________ _ Perullt Perclmt
2..43
6.1'
EICreted during shucking __________________________ _
12.2
3.23
EIcrcted 00 stunding 30 mlnutcs ___________________ _
26. 2
a.67
Rcsidual,
separating during 20 hours after standing
SO
minlltcs_._______________________________.___
_______
2. 9
4.57
Separated oySter meats SO minutes aftershlleking , ______________)
Ii. 2
Per Cll1lt .Per tent
, Represented 56.5 per cent of .tho contool.8 01 shell SO minutcs atter shucking.
I. 58
Percent
2. 00
1.96
1. 94
1.56 r
1. 52
' O. 14
1.
91
1. iO
1.40,.
1.08
.58 __________
.95
1.~3
:1;. 'I :BAODRIOLOG'Y AND OHE:M:ISTRY'OF -OYSTERS. '.; , 5 1
Alppurently the first !liquor in the: .shell· surrounding the: :Oysters
suIt, ~~ter, .containing ~ittle .0rg!IDic matter .and '8; ver:r
:small quantIty of; mtrogenous matenal. :Qurmg the .30-'mmute standL
Jng ,period . the meats" bled" freely, resulting ill .the separation
.of 26.~ per cent of· liquor. nuring .anadditional. 20-hoor stand~
in~r per~od~ut little furtht;r '''bleed~g'' occ~rred.. It issi~nific~~t
that the per(.'Cntage ofsohd matter m the lrquor pro~esslvely :ml.
iCl'Cnsed; , until the 'last portion .of liquor examined .a:tterstanding
fOI')20 hours'lhad a soli!1s content of 4:57 per 'cent:Theniti'ogen6us
constituents had increased ,also QUltil they represented nearly-half'of
the :totul solids present.
, . . . ;:
Shucked ,oysters .as prepared for market .are'never trn.nsportcd 'for
anY'distunce in their own liquor. After lbeing' washed inwuter' th~
ure,.passedover a skimmer, the excess liquid is jill'ained off, 'and tHe
oysters are packed ~'dry" in cans. Improper -draining results m
.adulteration. 'Waterso'-embodied gradually' takes up the -sblitls' until
it shows· a .composition closely approximating ·,thato£ the natural
'liquor found in ,the shell at the time of shucking. Therefore it Wou1Q
be extremely diflicult to. determine by examination of this liquid
wheUler it was, in fact, oyster liquor or unl'emoved wash water
unless the quantity of liquid that properly prepared oysters contained
.after shipment was' known.
.
,
.A.ccordinglYT for the purpose of studying in a more elaborate wily
the effect produced on volume and composition 'by various methods
of wus~ing, as well ,!-S on the free liq~or content. produced :by storlige
and shlpment,experlments were carrIed out durlllgthe oyster seasOns
lo£ 1921 to 1924, inclusive. These were of three types-: (1) TUb
wsshing .and ·soakingexperiments; (2) washing experiments, . using
II. blower,; .lLIld :(3) experlments to ~etermine- the effect on liquor:cohl.
tent produced -by storage and shIpment (p. 62). The results for
typ~s 1. and 2 are given in 'l'able"20.
.
I'
iW:ll~ . largely;.
,
1:.'
:
~ADLE ~,-EffQvt
Soun'C or oysters
af 'Washjllg oysters
Wushlng process
.i;~
tubs
.allci,'!¢.t,~
blc;werlJl
Gain In Loss'in 'Losslb •
volumo solids
salt
- - - ---
Free liquor on' ';
'i!1andmg'· ,
Per cent Per ce,1t Percent
l'otomao Rh'cr••••••• 2 gallons of oysters with 3 gallons
Do__".,-________• ,of water In tub, 1tlj hours,
2 gallons of oysters w th a gnlloDS - ....... ...
of water In tnb, 3 hours.
.
.00_______.------ 2,gnllons of oysters with 3 Gullons
14,0
of water In tub, 4M hours,
:
8,.1
Nansomond Rldgo, 20 gallons of oysters with 50 gal·
Chuckctuck, Va,
Ions of water In tub, 4 hours,
stirred evel'l' 15 minutes.
() ren t WicomicO' 20 gnllODS of oysters with 50 gal·
o.a
Ions of water In tub, 4 'hours,
Rlvor',Md.
Do_ _· _________• not stirred.
13,8
20 gallons ofoysters with 50 gal·
Ions of wuter In tub, 4 hours,
stirred frequently.
York Rlvcr,.Va ____ 20 gallons or oysters with 50 gnl·
5,6
Ions of water:in tub, 5 hours, .
without stirring.
20 gallons
of oysters
blown:
3 mlnutes
____•
___________ None,
West River·Choptnnk,
niver,
Md.'
•
Do _____________
6 mlnutcs __________________ None,
3 minutes _. _______ •____•
Potomac River _______
6.0
Do_______________
6 minutcs_________________
7.5
3 minutcs_________________ None.
Back River, Va.______
6 mlnute.q___________________
3,7
Back River and MobJaekB~ Va, 3 minutcs __________•••_____
N.
J_
Maurice
{vcr,
7.5
Do______________
6 .mlnutcs __________•___ •••__ •
8,7
_-_
, These oysters were thlu aud o( poor <Iunlity.
:
,
6.5
21.4 22.0
64.0 26.0
64.0
.15,0 .
72. 7
16.0
77.7 18mallqlllUltit)';
24.3
83.3
17.0
68. a .Nono.
APRrilciablo qurm­
tty.
None :at end of 18
hours.
e.
~o.
6,.2
62,5
.Do. 8.2
12,4
16.7
6.4
9,7
87.5
64.2
80.0
60.11
58,3
Do.
Do.
Do.
Do,
Do. 18.2
18.0
50.0
59.0
Do,
Do.
•
,
52
TECHNIOAIi, BUI:.LETIN ,M,
u. s: ,DEPT.
OF AGBIOULTUBE
As in all other washing experiments, ,there was some .gain in
volume .and .some loss in solids. The gain in volume was influenced
by the condition of the oysters. .Those used in the first and thir.d
.experiments with a blower were thin and did not absorb much
water, whereas those in the second and fourth experiments with the
,blower were plump and gained greatly in volume. It was con­
eluded from the first tub-washing experIment that the loss in solids
was pr.actically complete in three hours. The results of the third
tub-washing experiment indicated that the O'ain in volume can be
increased by a~itation of the .oysters in the tuK In none of the .eight
washing experIments was much free liquor excreted on standing.
Two experiments in which oysters were washed in tubs and two
in which blowers were used were conducted in 1922 and 1923, with
,the object of detel~mining (1) the change in volume and, composi­
tion of oysters subjected to .a reasonable commercial washing, (~)
any additional change by continuing the washing process until it
became in effect a soaking process, (3) the quantity of oyster solids
.dissolvedand carried off in the wash water, and (4) how much of
the water absorbed during washing is permanently retained and will
not appeal' as free li~uor after shipment.
The two tub-washmg experiments (No.5 and No.6) were con­
ducted along very similar lines. The only real difference between
them was that,in .No. 6, owing toa :scarcity ·of stock, it was necessary
to use, for the prolonged soaking period, a fresh lot of oysters on a
succeeding day.
In ,Ol·der to simulate commercial conditions wherein oysters are
allowed to collect and remain in tubs of fresh water from 2 to 4
hours, the oysters in experiment 5 were allowed .to remain in tubs
.of fresh lyater for 5 hours, being examined before washing, at the
end of 2% hours, and llt the end of 5 hours. In experiment 6 they
were soaked for a longer period, being examined before washing at
the end of 2 hours, and at the end of 6 hours. The oysters used in
experiment 5 were of unusmtlIy inferior quality,. the meats being
attenuated and badly torn. Those used in experiment 6 were of
better quality. .
In both experiments, before washing and at the end of .each of
the soaking periods, various determinations were made on the oysters
and the wash water. Each gallon of oysters was measured in a
standard gallon pot and weighed on accurate scales to 0.01 ounce.
The solids in the oysters, in the hydrant water used for washing,
and in the resulting wash water were also detcrmined. From the
results of these determinations the data presented in-Table 21 were
collected. In this table are given the maximum, minimum, and aver­
age weights per gallon of oysters before and after washing, the
computed gain in w.eight, and the computed gain in volume, the
loss jn solids, .and the computed quantity of water added during
w.ashing~
4
.1
"~OTERIOLOGY
T.ABLI!I
,AND OHEMISTRY OF OYSTERS
21.~haflge8 i1~volume, 1o,cight, and. lIOUds
ccmtmt of ,oysters durhag
wU08hing proce8ses
Weight per gallon
Defore wusWng
Experiment
Maxi·
mum
Mini·
mum
After wosblng
MIlXi·
mum
Avemge
Mini.
mum
Average
- - - - - - - - -----------Tub wosbingNo. 5:
Ounceo
]37
.First 8Onkinr, period._ ••••••••••••.•••
Second Bonk nl: period ••••••••••.•..••
Tub woshingNo. 6:
138.44
First sonkillg ~erlod •••••••••••••••••••
139
"Prolonged son Ing ,porlod ••.••••••••••
138.41
Blower wosblng'No. 6...••••.•.••••••••••••
137.59
Blower wosblng No. 6.•.•••••...••••••••••
OIt'Rcr&
134.79
Ounee.
135.82
Ouneu
136. 31
136.4
Ouneu
133..33
134.12
Ouneu
134. Sg
135.11
135.15
136.42
130.51
135.26
136.62
137.4
137.42
136.28
136.23
136.12
136. 89
137.15
133.62
133.5
135.08
134.03
134.34
134.6
13.'.82
135.35
Volume of cntlre lot
Experimont
I
Defore After
Wllsh· \ wnsh·
Ing
IlIg
Guin
Weight of entiro lot
Defore
woshing
After
woshing
Gain
Tub wlI..blllg No.5:
G(//Iall', GaliaM Gallon. Pereenl Ouneu
Oune.. Ouncu Per cent
3,395.5
First sonklll~ period•••••••.••
2
8.0
3.642.11 246.61
25
27
7.3
3,700.5.1 189.23
Second sonk IIg Pllrlod ••••.•• •••.•••• 28.1
1.35
5.05
5.2
Total sonking period •••••••••
13.4 '3;395~5" '3,831.34 435.84
25 1'28.35
3.35
12.8
Tub wushing No.6:
2,'i, 27.6
10.4
3,415.57 3,721.48 305.91
2.6
First sonking ITriod ••••••••••
9.0
Prolonged SOl' ng period._ ••
18.8 3,435.23 3,997.7
4.7
562. 47
16.4
~ I ~.7
Biower wnshlng No. 5_..•••..•.•
5.0
2,748.48 2,850.39 101.91
1
3.7
Blower wBsbing No.6 •••.•.••.•••
2, 725. 67 2, 783. 56
3.0
20 i 20.6
0.6
67.89
2.1
I
I
Solids In snmple
Experimont
Before
woshing
Solids In entire lot
Before
After
After
wllshing wosbing wnsbing
Loss
---- ---Tub wosbing No.5:
Pa' cenl Pcr cenl Ouneu
10.91
453.98
First SOnkin~ period...................
13.37
11.72
Second sonk ng period •••••••••••••••••••.•.•.••
'''453~9B'
Totn! sonking period .•••, .......................
Tub wnshing No.6;
14.43
11. 43
492.87
First SOIlking ~eriod •••.•••••.•••••••••
10.76
527.31
Prolonged SOil 'ing poriod. • •••••.•••••
15.35
1452.67
Blower wnshing No.5.••••..•••••••.•••••.•.••••••.•
347.25
Blower wnshillg NO.6••••••••••••••.•••••.:..••••••••
Ounce.
397.35
396.02
'372. 41
Ouneu
56.63
24.5
81.57
Per cent
12. 5
6.3
18.0
424.37
430.15
300.50
316.49
67.50
,97.16
62.17
30.76
13.,7
18.4
13.7
8.g
Solids pcr n"cragc gnllon
Experimont
Defore
washing
Ounces
Tub washing No.5:
18.16
First sonklntt perio~L •....••••••.•.•••
Second 80aklllg per,od ••••••••••.•.•.•
Total soaking period •••••••••••••••.•• ·..·iaiii·
Tub wosbing No.6:
19.72
First sonklngJrriod.••••••••.••.••••••
21.09
Prolonged so -ing peri "d ••.••••••••••
2263
Blo\ter wnshing No.5•••••••••••••••••••••
1i.36
Blower woshing No.6••••••••••••••••.••••
After
wnshing
Waterndded
during wosblnC
Loss
OU1lCU
.14.72
13.13
13.13
Ounc..
3.44
1. 59
5.03
Per cent
18.9
10.8
27.7
Oune..
303.24
213.76
517.41
Per cent
8.0
5.9
15:2
15.41
14.48
18.62
15.34
4.31
6.61
4.01
2.02
21.8
31.3
17.7
11.6
373.41
659.63
164.08
88.65
10.g
19.:2
5.8
3.2
, .corrected to include one-fourth gallon (34.81 ounccs) withdrawn for snmple •
• .calculated from the total solids contcnt found by analysis.
54
TEOHNioAL 'BUIXiETINM,
u.
S;:DEPT:OF 'AGRIOULTURE
;~·'Alth.ougn in' tuB-washing expe~'iment" 5, 12.5"per cent'.of We: solid's
was l.ost during the first washing'perioa; ·ab.out three-f.ourths ·Qf this
c.onsisted .of insQluble material, such as shell, sand,and shreds .of t.orn
meat. The quantity .of s.olids abstracted by thesecQnc1 washing was
smaller than that remQvedduring the first washing,but the actual
lQSS .of Qyswr SQlids was greater~ This is due tQ the fact that there
was very little insQluble material in the 24.5 .ounces .of SQlids' ab­
tracted by.the ,S~c.ond washing. In this experiment abQut 50 per
cent.of t.he salt. was remQv.ed in the first wash.ing and nearly aU o.f
it,in the ·sec.ond washing.. In tub-washing experiment ~ the· .incre~sei?
lP.' 'YQ]ume,"and weight and the lQSS .of SQ1ids are sQm~what greater
~hlm th.ose in .experime:Qt 5. This may be explained by the difference
ill'thequality:.of the .oysters.' . The results .of these experiments ilidi­
ca~ that JlIl ordjnaryiommercial washing causes gai~ in. vOluIii~;
additiQn .of water, and rem.oval .of SQlids. Practically all the jn­
SQluble solids are remQved by such .ordinary washing. It is CQn­
clude.dthat excessive washing is nQt needed tQ remQve sand and pieces
.of shell. PrQl~nged washing caused a prQgresSive reduction of SQlids.
Ve~'Y little free hquQrdevelQped .on the oysters after standing, .indi­
cl,!-tmg that much .of the added water was retained.
. The mam differences in pr.ocedure between the tWQ washing experi~
;ments with a blQwer (NQ. 5 and NQ. 6) and the tub-washing .experi­
,ments; except that a blQw.er is used, were that only one washing
periQd w.as used in . each experiment and nQ figures cQvering the
!analyses .of the wash water were cQllected. BQth bl.owing experi­
ments. were alike except that in the first the time .of bl.owing was ·five
minutes and in the secQnd seven minutes. The .oysters used in th~
secQnd blQwing experiment were .of PQQr quality and had recently
been frQzen.
In bQth sets .of experiments there were gains in v.olume imd weight,
additiQn of water, and lQSS .of SQlids, the latter being due t.o a leach­
ing out .of s.olids and n.ot tQ an apparent decrease frQm dilutiQn
,,:ltli water. (Taoles 22 and 23.) The results emphasize the 'fact
'that there is .only a small increase in v.olume when .oysters .of pOQr
~liali~yare s.oaked, but a marked 1QSS .of valuable oyster SQlids thr.ough
:lcpchlllg.
.
TABLI!l 22.-Quantity of solids present in wa8h. water and
a.erivca from Oy8ters
in, tub-washing ea:periments
Experiment
Soluble
Solids in solids
In
hydrnnt
wash
water
water
Soluble
solids
derived
from
oysters
Soluble
oyster Solids lost Insoluble
solids re­
solids in during moved
by
wash
washing washing
I
water
- - - - - -- - - --- - - -
..
'No.5:
"'" Second
First sO!lkln~
perio~ __________________ ~
soak ng
period_________"_______
.
No.6:
First soaking perlod.;__________'-_______
Prolonged soaking period ______________
I
Gram.• per Grams per Gralllsper
liter
liter
liter
Ouneu
.0.53
.53
3.08
2.76
2.55
2.23
16.32
21. !J2
.09
.09
5.19
5.01
5.1
4.92
32..28
46.2
Insoluble solids consisted of shell, sand, shredded meat, etc.
Ouncu
56.63
24.54
67.50
97.16
Ounces
40;31
2.62
35.22
50.00
!
,BAOTERI9t.bGY AN.D 9H1!1MISTRY OFO:r~~~~~
Ii
TADI,E 2:J.-Effeot of
1oo<thi-ng
(mcompositicm
of oysters
.
;,
-. :'
.
.
~
',-
~,'
~
, •~ "
"
a_. liquor
Free M
Methed and mater"..
cat L1q.
uor SoIIds Snit
Liquor
Meat
J'~
:~.tr.le ,,' ',ioJ.:
'I,-....,.--1---'-;----1---·
-T'
'""-,,-'-
Solids Salt Solids Salt 'Solids Salt
ink
SOI}~1
--'----'--'---1---'1-- - - - - - - - '- - - - - , - ' -----.--:..I-...:.:..::.....i
'I'ub
No.
P~
o~~~~.~:~~j-.~~~~~. C(~I <ti)' ::~
(.)
Oysters' after ,first'
wnshlng............ (I) 01. 4 8.6
,.oys\.ers aft,or ,second
. wash.lufi............ (.) 01.8 8, ~
~o I.galon C~,Of } ('J {04.3
0.7,
soaked oyst0 s......
93.6
6.4
w,nshlnl!
6:
Ptr
Gram.. 'Grania
ct:, lIt:,
::~~
•••••.•• ~..... 13. 37
••••••• ••••••• 11.61
::;; ::~ ::~ 13.37
t:~'::~
0: 11
O. 11 .•••••• '.,.'"
.05
3.48
0.15
10.91
.06
18.4"
, "
''
.•••••• ••••••• to. 25 (I)
3.74
.089.72 '(I)27.3
•••••••. "••••••••••• , •••••".••••••••••• , •••••••••••••••••••,'
•••••••••••••••••••••••••••••••••••••••. , ••••.••••••••••••
l~tr*~~~%~~:: :::::::::::::::::: ~: ~ 6~~~ :::::: :::::: :::::: :::::: ::::::::::::: ~~:;:: '.
Tub
washing
No.6:
."
'.oysters
before
2·hour
'wllsWng••, •••••;... (I)
90.9
9.1 •••••• ; ••••••• 15. 40
.18 4.69
.61 14.43 ".22 ' d!
.oysters after 2-hour
wnshlni_••••••. ~... ('J
90.8
O. 2 •••••• ~ ••••••. 12.21
.0-1 3.71
.21 11.,43
.06 20.'8'
.oystehrs
bofore 4·hour ( ) 01.8 8.2 •••••••••••••• ')6.32
' .
•3' '. ,'0 ;
was lng.............
.27 ~.4! .81 15.3,~. " 1
.oysters IIller 4·hour
wnshlng............ (I) 80.8 10.2 ••••••• '.'•.'. 11.62 «) 3.18 .10 10S6 • ~ ,29i \I
TIydmnt water....... ...... ...... ...... .09 ('J •••••••••••••.•••.•••••••••••••..-:: ••••••••••.
2·hour wash wllter...................... '5.19 1.15 ••••••••••_•••••••, ••••••••••••~ •••••••••_••
4·hourwashing
wash water...........".
Dlower
No.6:
.. "".' Ii. 01 . 1.25 ••••••••••••••••••••••••••••••••••••..••••••,
', .
.or~~::~.~=~~~~.~:~~~.
,.oYstersnfterblowJng.
Dlower washing No.6:
.oysters before blow·
2.2 ••••••.'.'.' .•••••••••••••••••••••••••••••••••••••• 16.47
4.0 •••••••••'.' ••••••••••••••••••••••••••••••••••••••_ 13.71
o;~fernai&irbiowfug: ~_: g:::::: :::::: ::::::: ::::::: ::::::: :::::: :::,:::1:::::: f,i:,,~~'
I
Almost nono :vlslblo.
, Not sapnmtod.
•Smnll quantlty.
.08
.,03
'. 0
~6.8,
.."
'. ,.
:~ ; 19.:d I
~
t..1< 'Or
t
<Trace.
'... ,
:1~~
~';
In all of the w;ashing experiments so far discussed the.,!!omp;ut~,,,
ti.on .of water added has been made on the ba!3is of gain in vplume
and iJ1. weight rather than .on the basis of the difference between ·the.
s.olids in the original material and th.ose in the washed materiaL J;n:
blower experiment 5, analyses of the oysters bef.ore and after :was4;:;
ing sh.owed a loss in solids of 16.8 per cent. Weighingsbefo,re 'aP4,
after blowing, however, showed that these .oysters did not take Upt
16.8 per cent of water but that the quantity of water actually incO~,."
porated was about 6 per cent. The fallacy of computing wa~r
added by s.olids lost is apparent, as it is based .on the supposition l
that the apparent reducti.on in, s.olids is due entirely to dilution:
with water and does n.ot take into account the a~tuall.oss .ofs.olubJ~;
solids rem.oved in the wash water.
J
,;;
WHAT C.oNSTITUTES
GOOD
WASHING
" 'l
.:
',:
During any effective washing pr.ocess there is some gain in v.olume
. and s.ome loss in solids and salt .of shucked oysters. These changes
depend upon so many fact.ors that it is difficult .to conclude, iIi ,one.
general statement, just what constitutes a proper washing without'
adulteration with water. The following conclusi.ons,how.ev'er, 'cl!-'n
be applied within certain limits :"
. .
" . . . ,
'1. In .oysters subjected t.o a reasonable washing witl1 freshwater,~
gains in v.olume from 3 to 10 per cent or more mllY take 'place,ae'.:
pending upon the .original conditi.on .of the .oysters, whether fat or
l
56
TEOHNICAL BULLETIN 64, U. S. DEPT. OF·AGRICULTURE
lean, upon the apparatus used, and upon the duration of the washing
pei·iod. At the same time there may be losses in solids varying
from 8 or 9 to 13 or 14 per cent or more. .Usually more than half
of tbe salt in the oysters is removed. Th.;; vse of a blower causes
less gain in volume and a smaller loss in sohLi.s than the use of tubs,
provided the blowing is not continued too long and the oysters are
not allowed to remain in the wash water after the blowing period is
ended. Furthermore, the use of a weak brine (about 0.5 to 1.5 per
cent salt solution) results in reducing the volume and causing an
apparent increase in solids content.
2. ·Wheft the oysters are subjected to a prolonged washing, which
actually constitutes a soaking process, there is a further gain in
volume and loss in solids and salt. During such a soaking process
the loss in solids is mostly a ~'emoyal of soluble solids, as the shell
pieces, sand, etc., are removed early in the washing process. In
other words, a pl'Olonged washing is not necessary to remove objec­
tionable insoluble matter. Once such material is removed the addi­
tional washing continues to remove solids from the oysters.
3. Solids are removed from the oysters by the wash water.
(Table 23.)
4. The greater part of the water absorbed by oysters is retained
during shipping und subsequent standing.
In addition to increasing the volume of the oysters, adding water,
and removing valuable solids, excessive washiwog takes away the
sea tang and fine flavor which has long placed oysters at the top of
the list of popular sea foods. Continned contact with fresh water
destroys their more desiru.ble physical characteristics. The rich,
creamy yellow color and firUl texture disappear and the oysters be­
come chalky white, bloated, and puffed, with soft, spongy tissues.
On cooking, such oysters rapidly diminish to less than their original
sizE'. and the meat becomes tough. and almost devoid of taste. Their
nutritive value is necessarily lowered by soaking in fresh water,
which removes large quantities of the soluble nitrogenous compounds
and cal'bohydrates. It seems probable that their digestibility is
also lowered, us the remaining solids are the tougher muscular and
fibrous tissues, which probably are less easily di~ested than the
more soluble ingredients removed by excessive washmg.
Under the term~of the Federal food and drugs act (91), it was the
duty of the Bureau of Chemistry to prevent the sale of adulterated
foods and to protect the consuming public f.rom fraud. Oysters lend
themselves readily to adulteration with water. It is very difficult to
draw a line between propel' washing, which will produce a clean,
marketable foodstuff, and soaking, which brings about adulteration
with water. At the same time washing is a necessary operation, which
can not be done without some loes of food constituents and addition
of water.
From the bacteriological standpoint, the best cleansing is performed
by: the use of a blower. From the chemical standpoint, the use of
a .blower for about three minutes, a weak brine (about 0.5 per cent)
being used as a washing medium, produces the least change in volume
and solids content. The most efIicient anel safest method of washing
oysters is by using a blower with salt water.
BAO~RIOLOGY
AND CHEMISTRY OF OYSTERS
57
SHIPPING OYSTERS
CAVSE OF DECOMPOSITION
PI'oducts having a high water content invariably spoil more rapidly
As the development of bacteria and other
lui('roorganisms responsible for the decomposition of foods is favored
by the pl'csence of moisture, any food containing a high percentage of
wnter is extremely perishable. Therefore, in handling and shipping
oysters precnutions to prevent spoiluge of the product between the
time of shipment and the time of consumption are necessar'y.
In this connection it is not illogical to compare oysters With milk.
Botl~ decompose l'llpidly 1£ not handled properly. Frequently each
is cOiisumed in the rltW state und each is capable of supporting the
growth of disease-producing bncterin, unless precautions are taken
to pl'event the ucceSs of such organisms to the food 01' to eliminate
them. The hygicnic pl'inciples ot hundling ordinarily applied to
mille apply to shucked oy'sters.
Oysters in the shell Will Temnin in good condition as long as they
live. By lTIC1tnS of its strong aelcluctol' muscle un oyster out of water
keeps its shell closed tight most of the time l although occasionally
oysters in a sack or barrel open their shells slightly during shipment
or storuge. If still alive snch oysters close theIr shells quickly when
elistm·bed. "When the oyster elies the adductor muscle is relaxed and
the shell remains open. Dead oysters decompose rapidly, one de­
composing oyster serving as a source of contamination to the entire
lot in the shippiu¥ contuiner. Kept in II cool place shell oysters will
remain alive and lD edible condition for compllrlltively long periods.
The renl bacteriological problem in shipping oysters is met in the
11Ilndling and storage of shucked oysters subseqnent to their treat­
ment in the shucking house.
In products having a high cltl'bohydl'llte content the predominat­
jng type of spoilnge is feI'lncntlltion. In protein products, such as
mellt and fish, it is putrefaction. Oysters contain both protein and
cllrbohycll'llte (glyC'ogen), so that during decomposition fermentation
IlS well as putrefaction tukes pillce.
After the death of the oyste-r,
which occurs soon after shucking, the glycogen present is hydrolyzed
to produce reducing sugn.rs. These sugars are readily fermentable
by bacteria of many species. The fermentation is productive of acid,
nminly lactic acid, und "soUt''' oysters. Although the production
of gas, acid, and a characteristic odor in decomposed oysters is re­
sponsible for their designation as SOUl' oysters, putrefaction is also
taking place.
An investigation by Hunter and Linden (48) showed that no
relation exists between the totnl number of aerobic bacteria present
Imd the (;OIidition of the oysters. As mltny as 30,000,000 uerobic
bacteria pel' cubic centimeter of oyster liquor were found in oysters
that were in good condition, as far ns decomposition was concerned .
.Only 12,000 aerobic bacteria pel' cubic centimeter of liquor we.re
found in others considered, because of odor and appearance, to be in
nn incipient state of decomposition. The factors mvolved influen~e
the bacterial count tt'cmendously. If oysters taken during the hiber­
nating season are studied, the number of aerobic bacteria present is
much smaller than when nonhibernating oysters are studied. The
Hum drier materials.
,58
-
TEOHNlejAI:. BUIlLETlN
64, U. S. DEPT. OF AGRICULTURE
introduction, during shucking, of bacteria that are not removed by
washing pl'Ovjdes a high count of microorganisms, even when the
oysters are fresh and in good condition. It is, therefore, futile to
atte~ptto grade oysters as to decomposition by the use of bacterial
cQtmts. It was apparent from this study that the spoil~ge of ,oysters
!€lepoods upon the ipresence and development of bacteria of certain
ltyptlS or gtoup~ ;rather than upon. the total number of organisms
:pr,esent. It was eviden.t that the total number oia.erobic bacteria
pI:esent was not ,as significant in jUdging the quality of shucked
oysters as might be the numbers of bacteria of certain groups 01'
species 'which cause fermentation or putrefaction.
-Further e.xperiments to determine the types or groups of bucteria
;re",ponsible for decomposition of shucked oysters showed .that cevtain
bacteriatisolated from decomposing shucked ovsters) when introduced
in pure ,culture into an oyster medium, prOduced foul, putrefuctive
.Qdors. These O1'ganisms were identified as members of the genera
Serratin," (wuter and soil bacteria producing red pigment), Pseu­
demonas (soil and waterbncteril1 producing a blue-gl1een pi~ment),
.Pro.teus, 'Clostddium (spore-forming obligate anaerobes), and
Bacillus (aerobic spore-forming bacteria). Certain other micro­
iOl'gllnisms pl'oduced acidity 01' sour odor, or both, in pure cultures
grown Un oyster medium. The microorganisms were members '0£ the
lactose-fermenting group of bacteria,' such as Ae1'o'btLctel' ae1'og.ene$,
A. cloacae and EsoltM'iscMa col·i, lactobacilli, streptococci, and yeasts.
A great JIlany other water and soil bacteria, which aPJ?arently had
·no effect upon oysters, were isolated fl'om the decomposlDg material.
The majority belonged to the genera Achromobucter, Eberthella, and
Flayobacterium.
A study indicated that the decomposition of shucked oysters in the
beginning is due to the activities of some members of the Serratia,
Pseudomonas, Protells,Clostridinm, Bacillus, Aerobacter, and
Eschel'ischia groups of bacteri!t. Later in the cqurse .of the spoilage
streptococci, lactobacilli, nnd yeasts find more suitable conditions for
development, until in the very lnte stages of decomposition the high
dilution plate cultures mnde from the oysters, which became very
sour and putrid, contained nlmost exclusively colonies of these three
groups of organisms.
The information now at hand, which may be changed ,by further
research, indicates that both fermentation and putrefaction take
,place 'during the decomposition of oysters and that· the spoilage is
dueto.the action of ordinary water and soil bacteria, with such
intestinal bacteria as may be present ,from pollution with sewage.
RATE OF DECOMPOSlTlON
"i The rapidity with which shucked oysters decompose depends upon
-the conditions under which they are handled. The fact tnat shucked
oysters are a perishable product means that spoilage advances very:
quickly unless. precautions are taken to prevent it. The results of
.Jaboratory experiments to determine ,the effect of washing in fresh
water and brmeand ·of the use of ice upon the keeping quality of
shucked oysters are given in Table 2 4 . '
.
;, ;<,fT.!:u llomenclature (or bncterln ns presented In n<lrgey's Mnnual ot Determlnatlv.e
Bacteriology by n comiIrlttee ot the Society of American Bncterlologlsts (80) Is used.
p~O;rEJUOLOG¥
,A;N"D
c:~m,pS~B.Y
~A1l;LE, ,24.-:;Rela.tl()l~ ,bchveoll trca~trIc/tt
, '.
,l
•
,
".
OF
,O.Y~TEllS
.
of oyst,er8!1-!ld titlle .,alld progres~.9'
. . ,
:
. spoilage
' , '
.
0"
'EXPERIMENT 1 (Ol:STERS OONSTAN'l'LY)IN J.QE; TEM,PERAT.{!,RESjI3TO
.Tor
\t
DRY or Day or
storage stomge
011 which 011 which
TrCllllllollt or oystors
N~
h.~
6/1°1.:); ;:
::K!~..
stllie
I=
sour,.,<
--~I--------------------------------------------------II--~~~
ullwnshel!; oystors
_______________________________________ _
,3
111
Shells uuwl\shed; oystw:s wnshod In rresh wl\ter _____________________ ~ ________ _
4
12
3 . Shells unwnshed; uysters wlIshcliln brlno ____________________________________ _
4.
14
4 Shells wll!Ihcll; oysters ullwnsheIL________________________________._____________
3
14
5
wnshod; oystors wlL,heliln rrosh Willer _______________________ .._________ .
4'
14
6, .Sholls wllshod; oysters wll!Ihed III hrllle_______________________________________
'~:
ShelL~
III1WIL~he!L_.
~llOlIs
4
EXP~RIMENT
1
8
o
10
11
I!!
13.
14
15
111
17
18
2 (NO IOE' USED; TEMl'ERA'rURES 51 TO 14° .F..)
Shells ullwlIshot!; oysters ullw35he(L_______________________________________ _
Sholls ullwnshell; oysters wIL~hCd III rrosh wlltor . ______________________ • _______
Sholls ullwoshell; oysters wushedlll brillo ______.---------.------.,.-__________ _
Shells wushe(I;·oysters unwllshed. ________._.____________________ • __ • __ • ______
Shells wl\shed; oysters wushed ill rresh wRter ________________________ • ________
Shells Wll!lljL'tI; oysters wll!lbed.\11 briIlO--_____________ _______________________ _
c
~
EXPEU~MENT
,
.~4
1
2
2
2
2
2
3 (ICED ON A.LTEltNA'l'E DAYS; TEMI'ERATUUES46 TO 16° F.)
Shells ulI\v(lShed; oysters IIl1wll!lhe(t. __ • ______________________________________ _
Shells ullwnshctl; oysters wnshod ill rresh wRtor ______________________________ _
Shells unwnshcd; oysters wnshed ill bcllle ____________________________________ _
Shells wnsbe(l; oysters Ullwll!lhotL. __________________________________________ _
Sbells wnsbcd; oystors wnshed In (resh wllter ________________________________ _
Shells wnshed; oyslerswnshed In brhlo _______________________________________ _
2
2
2
2
2
2
8
. 7
7.
·8
,7
7
EX]'EUIMENT 4 (NO IOE USED; T.EM.PERATURES 40 TO 05° F.)
19
20
21
Shells unwashed; oysters unwOshctl ___________________________________________ 1
Shclls ullwnshot!; oysters wnshed ill rmsh wRter _____________________._________ _
Shelis ullwnshcd; oysters washed III brlllo ____________________________________ _
~I
4
3
4
Apparently the washing, befol'C and after shucking, had little
effect upon the keeping quality. The oysters became stale or sour
on about the same duy, regardless of the method of washing. Where
ice was used constn.ntly the oysters developed a slightly abnormal
odor on the third and fourth days, but remained in this condition
until the tenth, twelfth, and fourteenth dttys. These oysters did not,
in the late stages of decomposition, develop the chJl.racteristic sour
odQr Imd gussyappeamnce of badly decomposed oysters, but de­
veloped a strong, rank, disagreeable odor and a .milky appearance.
In cuses where no ice was used the oysters changed very rapidly
from normal to a condition described us stale and within three or
four days after shuckin~ to a sour-smelling, nauseating, gassy, and
milky appearing conditlOn, unmistakably characteristic of spoiled
oysters.
'
. The use of ice on alternate days simplY retarded, temporarily the
growth of the bacteria causing spoilage, but the progress of the
decomposition on the days when no ice was used was so rapid that the
spoilage proceeded gradmtlly, regardless of the temperature. A con­
dition of sourness was reached on the seventh or eighth day. It is
evident that rupid spoilage takes place unless oysters are held at the
60
TECHNICAL BULLETIN
64,
U. S. DEPT. OF :AGRICULTURE
proper refrigerating temperatures. If shucked oysters are handled
properly during shipment and stora~e, they can be shipped from the
Atlantic coast to points in. the l\iIidclle West.
DETECTION OF SPOILAGE
'Probably the best method of detecting spoilnge in shucked oysters
is by the use of the senses of smell and sight; that is, the so-called
organoleJ)tic test. Decomposed oysters have a characteristic odor
and appearance that is unmistakable to anyone familiar with the
fresh product. Certainly no other test is needed for the detection of
spoilage in oysters that have renched an advanced stnge of decom­
position. It is not unusual, however, to find shucked oysters that have
pussed fmm the perff'··1;ly fresh stnge to the incipient stn~es of de­
composition. In judg~" the quality of such oysters, which, for the
lack of a better word,llIt;;'e been designated as " stale," there is oppor­
tunity for personal opinion, likes, and dislikes to play a part. In
view of this, Hunter and Linden (48) attempted to correlate some
definite laboratory test with the physical condition of the oysters.
An attempt to establish It relationship between the total counts of
bactet"ia and the condition of the oysters failed (p. 57). A study
of the relationship between the hyc1rogcn-ion concentration of oy&ier
liquor anel the stage of decomposition was more productive of
results. The hydrogen-ion concentration of the oyster liquor was de­
termined, IlS Ilccurately IlS the method would permit, by testing, in
Il porcelain plate, It drop of the ljquor with certain hydrogen-ion
indicators described by Clark !Lnd Lubs (~8). The results of these
tests Ill'e given in Table 25.
TABI.E
25.-LilllitiIlU JIll
·1.1(/lflC.~
for {IOo(l., stale, a-nd sour oyster8
EXPERi.MENT 1
pH values
Jar
No.
Treatment
Good
oysters
1
2
3
4
5
6
Shells unwashed; oysters unwllsholl ___________________
Shells unwllshed; oysters wllshed in fresh wlltor _______
Shells unwllshell; oysters washed in brino _____________
Sholls wlIslmd; oysters unwlIsl1od ______________________
Shells wllshed; oyslers wlIshod In fresh wllter __________
Sholls was hod; oystors wllShod in hrlno..______________
Stille
oysters
6.8-6. ()'5 6.0&-5.3
6.6-6. 15 6.1&-5.5
6. 2-6.0
6. 0 -5.. 25
0.5-6. 15 6.1&-5.4
6. 6-6. 05 It 05-5. 2
6. 3-6. 0 16.0 -5.2
Slightly
sour
oysters
5.3-5.0
-----------
----------5.4-5.3
5.2-5.1
5.2-5.0
Sour
oysters
5. 0 --1.0
5.5 -5.0
5.25-5.0
5.3 -5.2
5.1
5.0
EXPERIMENT 2
7
8
9
.10
Shells unwllshed; oysters unwashed __________________ _
Shells unwlIshed; oysters washed In frC3h wllter _______
Shells unwlIshell; oysters washed in brlno ____________ _
Shells washed; oysters unwashed _____ •______________ _
11 Shells wllsholl; oysters washed in fresh w8ter _________ _
12 Shells washed; oysters washed in hrlno________________
7.!Hl.6
6. 8-6. 15
It 7-5. S
i. (H). 25
6. 8-5. U
6.6-6.1
6. 6 -.5.0
6. 1/H. 75
5.8 -1.8
6.25-4.9
5. G -1.75
6.1 -1.9
__________ _
__________ _
__________ _
__________ _
__________ _
__________ _
5.0 --1.7
4•.7/H.7
4.8-1.7
4.0 -1.7
4:76-4.7
4.0 -1.7
61
BAOTERIQJ:,OGY AND OREMISTRY OF OYSTERS,
TABLE 25.-LiIll4tillg pH 'values 10/' goocl, Btale,
allet 80U/' oYBter8~Contlnued
EXPERIMENT 3
pH values
Jar
No.
13
H
16
10
17
18
',I'reatmont
Shulls IIIlWII.,llOd; oyslurs unwllshud .._____ ._..________
Sholls nnwushod; 0Y8l.... wllsh..d in lrush w,\lor _______
Shulls IInw'L,I",d; oyslor'j wlishod in britlO__ •__• _____ ._
Sholls w'L,hod; oyslors IInw'L'hod ______ •_______________
Sholls wfL,hud; oyslors wflshod ill Irosh wuler __________
Shells washed; oyslors wflsh,\d in brino___----------.--
Qood
oyslurs
Stalu
oysturs
7.lHJ. 5
6. 8-6. 5
6.tHI.:1
6.8-6.·1
6. (HI. 3
6.5-6. 25
6.fi -5.2
0.5 -5.4
0.3-5.2
6,4 -5,3
6.3 -5.3
6. 25-6. 3
Slightly
sour
oyslers
-- --------------------.----.--­
.---.------­
---------------------
Sour
oysters
5.2 -4.7
5.4-4.7
5.2 -4,7
5.3 -4.7
5.3-4.7
5.3-4.7
EXPEIUMENT 4
19
20
!
Shells unwflshud; oysters unwlIshOd _________ ._._______
Sholl:; Ullwll..'ihud; oyslnrs wnshod in fresh wnt"r .______
oyslars wllshod in brine_____________
~~~~~IIIWIIShCd;
16.1l-5. 8
11. H-5. 11
tI. H-5. 6
5.8 -5. I '--_________
5. 6 -5.0 ___________
6 -4. 9 1___________
~.
1
15.1
-4.7
5. 0 -4.7
4. 9 -4.6
The limiting hydrogen-ion concenh'ation values, whicll were ftiirly
definite, may be of some assistance in determining thc quality of
shucked oysters. A. hydrogen-ion concentration value between 5.6
and 6.1 apparently represents a zone wherein oysters nre passin"
from good to staJe. Oysters passing from stale to sour or putrid ha~
hydrogen-ion conccntt'ution vulues between 4.9 and 5.3. Oyster's
having a hydrogen-ion concentration of less than 5.0 may be con­
sidet'ed usuaUy to be in an advanced stage of decompositlOn. The
limited number of determinations and the restricted area from which
the oysters used wet.·e collected do not justify the unqualified state­
ment thn,t these hydrogen-ion concentration values may be llJ;>plied
to shucked oysters ft'om nIl localities hancUed tmder all conditions.
The results obtained, howevcl', were consistent enough to indicate that
the hydrogcn-ion concentrations given are si~nificant and may be
of value in examining shucked oysters of questlOnable quality.
PREVENTION OF SPOILAGE
In order to prevent spoilage during shipment shucked oysters
must bc kept Itt tempemtures low enough to prevent, or at least to
returd, the development of microorganisms (15, 71). Shucked oys­
ters shipped and stored at temperatures below 50° F., preferably
below 45°, should reach the consumer in good condition. Washing
hilS a decided effect upon the quality of shucked oysters, .especially
on the number of organismspresent (p. 47), but it is impossible to
free oysters entirely of bactena by washing (p. 47). The two main
factors in the prevention of spoilage are thellNoidance of contami­
nation and the liberal use of ice.
Modern methods of shipping shucked oysters in nonreturnable
containers have done away with the objectionable practice of placing
ice in contact with the oysters. Oysters are now packed " dry" in
1, 2, or 5 gallon tin cans fitted with friction tops and in quart and
pint con tamers. These cans, which are cylindrical, are placed in
rectangular or square wooden boxes or in barrels. Below and above
the cun, und in the corners around it, is placed plenty of crushed ice,
which does not come in contact with the oysters but keeps them
62:)
TEOHN'lCAL·BtrLLETIN M, 11. S. DEPT. OF. AGRICUIlTURE
cooled to the desired ,temperature ,if they are re-iced, as they should
be, during transit. Unless shucked oysters are to be kept in a re­
frIgerator or cold-storage plant in the l:etail store, the same prin­
ciple of refrigeration should be applied there as during shipment.
Ice .should not be added directly to the oysters, but they should be
kept in suitable metal containers surrounded by ice. Carelessne$s
on the part of the retailer may nullify all the efforts which have
been taken in preparing the product.
SIGNIFICANCE OF .. FREELlQU.OR "
In commercial practice there is alwtlys the possibility that drainin~
and skimming may not be properly carried out and that quantities of
wash water may be carried into the shipping container to adulterate
the oysters during shipment and storage. Many experiments were
conducted in the Bureau of Chemistry to determine the effect of
udding known qua.ntities of water to shucked stock in the shipping
container. For example, four experiments were tmdertaken to ascer~
tain whether or not properly skimmed oysters developed free liquor
during shipment or storage and to determine how far oyster& ·if
udulterated with fresh wuter, either through deliberate intent. 01' us
a result of imllroper dl'llining, would absorb this excess of liq~iu..
dming stor~ge or shipment.
,
•
In each experiment properly skimmed, " dry" oysters were packed "
in I-gallon friction-top cans. Other cans were filled with oysters'
frQm the same batch, known quantities of water being udded. In each
experiment foul' sets of two cans each were prepared. (Table.26.) In
the first und fourth experiments hydrant water was used as !In
adulterant. In the second and third experiments wush water from
blower was used, us it was ussumed that improperly drained oysters
would be udulterated with such a solution of oyster solids, The cnns
ill the first experiment were shipped direct from Norfolk, Vu., to
Baltimore, Md. Those in the other three experiments were shipped
from Crisfield, Md., and from Norfolk, V n., to Baltimore, Md., via
BufFalo l N. Y., where they were re-iced.
.
In examining the oysters after shipment a record wns taken of
their appearance and determinations were made of the quantity of
free liquor and the percentage of .solids und salt in the entire sa~ple.
T~le data collected, are presented III Table 26.
.
a
TARLE
26.-Appea/'llllcc of and quantity of free liquor, solids, aml salt in 1vashed
and druhICd shucked oyster8 to 1vhich 10ater 10asa(lded
"DRY" OYSTERS (B"\.CK RIVER AND MOlllACK ,BAY STANDARDS),
Ex[lCri­
mnnl
No.
r
Ap[lCnmnco
",W .".d__ -------------
I
Free
liquor Splids'
"
Salt' Decrease
in solids
- - - - --,-
Per cenl Per Celli Per Ct111 .£er ..cenl
Pl!J8 5 [lCr cent hydrant wnter__
'I:
..
Condition nIter shipment
'Method or trenUng
{SOlid pack; littlo free liquor on { 0.0\)
1.2
the surfnco.
_____do_.________________________
pnck; some free mueiPlus 10 [lCr cent hydrnnt wnter_ {SOlid
Juginous liquor on surfuco.
_____d,o_________________________
P1UB15 [lCrcont hydmnt wntor __
-
DolerUliplltions mude on entire sample.
!"
~ 14.52
0.17'
0.0
13.76
.16
5.2
2.0
4.0
2.2
~ 13.20
3.5
12.48
5.1
.15·
U,I
.14
13.9
;63
BAOTERIOLOGY AND OREMISTRY ,OF OYSTERS
,TABLE 26:-Appea.rance of and qttalltitv.of tree liquor, solUI., ,and 8alt in 10a8hell
and clrai"ll6/l 8hucked oysters to 11J1~ich 10a.ter waeadded-Continued
-"DRY" OYSTERS (GREAT WIOOMIOO STANDARDS)
..
..
Ex-
iperl~
,Ulont
l'{o.
"2
,
Condition after shIpment
r.."
Metbod of trcating
-• ApJ)2llranOll
Free
liquor Solids I
'Salt l
Decrease
in solids
- -- - - - -
Per cent Per 'cent Per cent Per ctnt
. M'L________ ----- Sorno freD liquor on surfnco____
PIllS 10 \'Cr cent wnter tnkon
from b oWerllftor wnalling.
PIllS 15 \,er cont wnter taken
frolll b Ol\'orllftcr wasblng.
1'1118 20 \,or cellt wuler takon
Irolll b ower lifter wll8hlng.
7.4
Free Ilquor, about linch deep,
13. .1
on slIrfoco.
18. 7
Lnrgol qunntlty of frco liquor;
18.6
sloppy rncl.:.
.
About 2 nebos of frco liquor { 24.5
on surfaco; sloppy pnck.
23.5
i4.6
} 13.70
0.03
0.0
} 12.0
11.39
.03
.03
It!. 8
} 10.78
.03
21.3
0.0
7.'
"DItY" OYSTERS (YORK RIVER STANDARPS)
t
3
No wnter added. ______________ [Solid pack; very little free II'luor \·15Ihle.
PillS 10 ~r COllt wnter tnken :lomo freD liquor on surfaco____
from II owor nftor wllShing.
Plus 15 ~r t'OlIt wlltor tnkoll Mucb frco liquor; somewhat
sloppy.
lrom h owor IIltor wnshln\:.
I'lus 20 ~r CI1nt wntor tnken Lorgo quantity qf free liquor;
from b owor altor wasbing.
sloppy l'ack.
r-"., " '- - - - - -
l"
6.0
11: 8
11.0
15.1
17.2 20.5 20.4
In.
1
o.ru
10.2
.03
8.1
U.5
.03
lU
} 9.0
.03
18..9
}
"DRY" OYSTERS (JAMES RIVER S.ELECTS)
Free liquor, nbout 3i inuh deep,
on surfllt'e.
'I'ius 10 per t'OlIt hydnmt water_ Free liquor, about linch deep,
on snrfnce.
4
Pins 15por COllt hydrant wlltor_ Free liquor, abllut 1~ Inches
decp. on surfllco.
Plus 20 per C\!nt bydmnt water_ j;'reo Ilquor, n!mnt 2 incbes
deop, on snrlllt'll.
_ --
6.6
1:1.36
0.09
0.0
12.~
11.111
.12
:I.6ol
20.1
10. II
.12
11.9
24.0
10.23
.13
17.2
........
I
Determlnntions mnde on on tire snmplo. t 'l'b~so oysters wero frozon hotwcen Ilncking and examinntion. In experiments 2 and 3 the added wash water was not absorbed
us in experiment 1, where the maximum quantity of free liquor was
5.1 pel' cent in the samples adulterated with 15 pel' cent added water.
'rhis may be explained by the use as an adulteraDt, in experiments 2
und 3, ofa liquid which already contained oyster solids and was not
ensily absorbed, and by the fact that the oysters in these experiments
were :of low solids content.
Several conclusions may be drawn from these experiments: If
plump, fat.oysters of fairly high solids content 'are used, a reasonable
. q uantity of water added as an adulterant will be absorbed and re­
tained, not to be given up as free liquor upon storage. The added
water will .dissolve oyster solids and will become, in fact, a thick,
viscous solution of soluble oyster material. The detection of such
adulteration by chemical analysis is difficult. [ f lean oysters of
fairly low solids content are used, the added water is not absorbed
and can readily be detected as free liquor after storage. In lsuch
cases the quantity of free liquor is proportionate .to and mayeqpal
lthe quantityo£ water added. Even oysters to which no water"has
been intentionally added will develop some free liquor upon 'stand­
',lng, but this is rlll'ely in. excess of .5 per cent by weight, a fait 'aver­
Ilge for the quantity of free liquor on properly washed and packed
TEGHNIOAL BULLETIN M~ U. S. J)EPT. OF AGRIGULTURE
oysters. When only small quantities of water are added a higher
proportion is absorbed than when large quantities are added. Data
at hand indicate that oysters showing free liquor in excess of 10 per
cent ,by volume nre adulterated with water. As oysters ,do not nor­
mally develop much more than 5 per cent of free liquor, it is safe
to state that 10 per cent indicates adulteration. As the solids, salt,
and moisture contents \'!lry greatly ,with the locality and with the
season of the year; making it difficult always to detect Ildulteration
with wuter by mOisture and suIt determinations, it is probable that
the examinatlOn of shucked oysters for free liquor is a more reliable
menns of detecting adulteratIOn. .At least, such determinations are
confirmatory of results obtained by eXlUnining them for total solids
and suIt.
GREEN OYSTERS
Pl'oblluly no phase of the biology of the oystm' lias been subject to
more controversy than has the subject of green oysters, Some of the
early investigators stated that the green coloration in oysters was due
to the presence of copper. Others contradicted this statement. This
dh'cl'sity of opinion is explained, to a greatext.ent, by the fact that
-thll oysters used for study were from different source>; and that the
green color was not the snrne .in all the oysters used. ·When the exist­
ence of 1Il01'C than one type of green oysters was finally established
there Ilppeul'cd to be more ngreement among biologists regarding
the cause of each type.
It is now known that there nrc two distinct types of green oysters.
In one the color .is distributed in strea.ks Ilr.d patches over the liver
or the viscomI part of the body. Sometimes the entire body has a
greenish tinge. This light bluish gl'een, suggestive of the color of
cel'tain cOpper suits, led to inyestigations to prove that it was due
to the presence of copper in the body of the oyster.
In the other type of green oyster the color is restricted to the gills
and mantle. The coloration in slIch oysters is usually dark olive green,
somewhat suggesti ve of chlorC!phyli, Oysters pxhibiting this condi­
tion are referred to as green gllled, green bearded, or green finned.
COLORED BY COPPER
Prior to 1894, many of the investigations repOl'ted ill the literature
appear' to ha.ve been conducted as a.ttacks upon the popular theory
thut the greening of oysters was due to copper. In 1894, Bulstrode
(931) reported that oysters from Falmouth and Truro, England,
which showed thc bluish-green ~oloration in patches, were entirely
different from those from Murennes, France, in which the green color
was restricted to the gills 01' mantle. Samples of the blue-green
oysters were collected by Bulstroc1e, who sent them to Thorpe for
analysis, Thorpe (84) stated that "there is no question that the
greenness of certain oysters, especially of those found in Falmouth
and Truro waters, is due to copper." Herdman and Boyce (493) found
copper in qunntities up to four times the normal in green American
oysters. The copper reaction coincided histologically with the pres­
ence of green granulnr leucocytes, Consequently, the copper was
.regarded as the cause of the green C0101:. The investigators also found
that the copper content of normal" white" European oysters varied
\
BAOTERIOLOGY AND 'OHEMISTRY OF OYSTERS
65
from 0.25 to 0.66 milligram :per oyster, with an ,l~verageof ,about
0.4 milligram. Oysters exhibIting green patches on ,the body con­
tained 3.52 milligrams of copper, about, nine times that found in
the normal oyster. Green American oysters contained 2.63 milligrams
of copper :per oyster; normal oysters from the same source contained
only 0.7 mIlligram of copper. By microchemical methods Herdman
and Boyce demonstrated the presence of excessive quamtities of cop­
per in the green tissues of American oysters. Experiments in which
certain ,metallic salts were added to the water in which oysters were
floated were not successful in producing the green color, althouO'h
there were somo ,indications of green color in ilie floated oysters. Is
a result ,of their work, Herdman and Boyce were positive.that the
bluish-green color appearing in spots .on the body of the American
and English oyster was due to copper.
Pease (69), N elsoll (65), and ,some others were equally positive
that this green color was not due to copper. Pease reported that
all oysters contain some copper and that of 60 samples examined in
his laboratory the copper content varied from 2 to 782 milligrams
per 1,000 grams. The smallest quantity of copper in green oysters
was 107 milligrams per 1,000 grams of oy,ster and the greatest in
normal oysters WIIS 295 milligrams per 1,000 grams. In other words,
normal oysters sometimes contain more copper than do green oysters.
Pease stnted that high copper content and greening always appellr
together in oy,sters, the average copper content for all green oysters
bemg 391 milligrnms pel' 1,000 grams ,and the average for all normal
oysters only 49 milligrams pel' 1,000 grams. Nelson believed that the
green color was not due to copper, even though he found .in green
oysters foul' or five times as much copper as was found in normal
oysters.
In 1917, Stewart (unpublished report) stated that the blui,sh-green
color which permeates the. entire body of the oyster is undoubtedly
due to the presence of copper in excess of the normal amount.
The preponderance of the evidence reported in the .literature favors
the view that the bluish-green color in patches on the bodies of
oysters is due to the presence of .an excessively large quantity of
copper. The source of the copper m the sea water clln not be ,satis­
factorily explained. It has been suggested that it is derived from
tmde wastes, from the cop-pel' bottoms of vessels, from drainage
through copper-bearing ,SOlI, and from other sources. Regardless
of the source, however, there 4'3 no doubt that comparatively large
quantities occur in.green oysters. This green color is not easily
remm'ec1 from the body of the shellfi'sh. Green oysters transplanted
to other waters than those in which they were grown remain green
for long periods of time.
The question of injury to health from the consumption of oyster,s
contaimng copper is also an open one. Many investigators have
claimed that the quantity of copper present is too mmute to be
injurious unless a great many more oysters are eaten than are usually
consumed by one person. The principal objections to ,such oysters
have been tneir appearance nnr.l pecuHartaste. Stewart (unpublished
report) stated that he had eaten ovsters containing as much as 1,000
parts per million of copper with
apparent discomfort. However,
no
78955°-28-5
66
TEOHNIOAL 13UIlL."ETIN 64, U~
s.
DEPT. OF AGIUOULTURE
it can not be recommended that oysters containing much copper
be eaten. UntH more information is obtained regarding possible
danger ito health from copper-green oyster.s, it ispr.obably well to
view such shellfish with suspicion.
GREEN GILLED
Oysters exhibiting a dllrk~green coloration in the gills and mantle
have been known and relished for .a long time in Fmnce. Such
oysters, called "huitres de Marennest were produced ttrtificially in
tanks .or "c1aires," as they brought a higher price in the French
market than did the normal white oysters. In comparatively recent
yeRI's green~gilled oysters have been recognized in the United States,
but not with the favor shown them in Europe. In the United States
green-gilled oysters .arc usually viewed with suspicion by thc con­
sumer and hence are almost unmarketable.
As early as 1820 Gaillon (38) published a report of his studies on
9rcen-~illed. oysters. Later many biologists, includi,!!$ Puysegur
\1~), Rlder (78), Lankester (59), Bulstrode (931), and Herdman and
Boyce ~12) confirmed GailIon's conclusion that thc~!een coloration
in thf:' gIlls of the oyster is due to .the presence of theeliatom N avietda
ost.1'em'ia..
In the fall and early winter of 1915, the appearance of gr(len~gilled
oysters in Lynnhaven. Bay, Va., led the United States Bureau of
Fisheries to conduct investigations to learn whether ,or not these
oysters were identical with those of Marennes. Mitchell and Barney
(63) .concluded that .the Chesapeake green-gilled oyster was the SaIne
as the MareIUles oyster.
Apparently investigators agree that the color is due to the inges­
tion of diatoms by oysters, not to the presence of iron or copper.
They agree also that such greening does not make the oysters
injurious to health und that, if the prejudice of the public for such
an abnormal-appearing product can be overcome, there is no reason
why green-gilled oysters should not find as ready a market as white
oysters. '1'he sanitary quality of the oysters can not be correlated
with the green color of the gills, as this color may appear in fresh,
wholesome shelEish from unpolluted sources. In the United States
it is simply a case of nature producing what is sought by artificial
means in France.
As it is well established that the color in green-gilled oystel's is due
to microscopic plants, which are not injurious when eaten, and as
the presence of this color in no way indicates that the oysters are
either decomposed or polluted, there can be no objection to the sale
of green-gilled oysters because they are green. The standards for
decomposItion and pollution that .are applied to all other oysters
should be applied to ~reen oysters, no m!ttter whether their color j!';
due to copper or to the presence of the diatom Navic,ltla fUllifOl'17LZS
val'. ostl'eal'ia.
PINK OYSTERS
The production of a pink color in shucked oystel'sduring transit
storage, even at low temperature, is frequently the cause of serious
finnncial 10s3 to shippers and denIers. In 1914, Bate.s and Round
suggested that this pink ('olol' was produced by a yeastlike fungus.
01'
,. BAOTERIOLOGY AND OHEMISTRY OF OYSTERS
67
A detailed report of the cause of the pink color, with suggestions for
its control, wa,s later presented by Hunter (47).
Upon reaching their destination oysters shipped froin points on
the Atlantic coast to the Middle 1Vest often show u coral pink or
reddish color in the liquor or on the meat. Sometimes thIS color
is not evident to the jobber or distributor who receives the oyster,s
nbout two days after shucking and who repacks and reships them to
retailers in Ius territory. Neither does the color appear immediately
after shucking and before shipping. Investigation demonstrated
that the color ,yu,s due to the development of a pink yeast, which
gl"OWS readily and produces pi~ment at low temperatures. The
color produced in the oysters has been variously reported as a bright
red or a faint pink. The prevailin~ shade seems to be a c.oral pink.
After the cause of the color ha<1 been determined, studies were
conducted to a,scertain the source of the contamination and to find
some method of control. The pink yeast was found on the bin,s,
benches, tubs, wheelbarrows, and other utensils in and about the
oyster-shucking house. It was particularly abundant in the accu­
l"llulated dust and dirt within the bins. The yea,st could be .re­
covered also from oysters, especially after they had been in contact
with infected objects. Although the yeast was present in oysters
taken directly from the growing areas, the number of such organ­
isms was very small. The re,sults indicated that the chance of con­
tamination was far greater within the shucking house than on the
beds. Repeated examinations of samples of surface and b.ottom
water from neal' the oyster-growing areas rarely ,revealed the pres­
ence of the pink yea,st. Samples of water collected while shells
from the shucking house were being spread on the beds to serve
as cultch for the collection of oyster spat contained the pink yeast.
It was indicated that the yeast collected on the shells during han­
cHing in the shucking house were being returned to the waters from
which oyster,s were lx:ing taken. It was impossible .to recoyel' the
pink yeast from samples of mud and sand collected from the oyster
beds,
The yeast isolated from the pink oysters did not ferment any of
the carbohydrates commonly used in the laboratory, nor did it
seem to have any effect upon the oysters other than the production
of the pink color. The yeast was very resistant to drying. The
pink yeast is easily killed by formaldehyde in a dilution of 1 part
of formaldehyde gas to 2,500 parts of water. Adding 1 part of
('ommercial formalin, which is a 40 per cent solution of formaldehyde.
to 1,000 parts of water gives a 1-2,500 dilution of formaldehyde:
A.s a method of control it is recommended that all bins, benches, tubs,
other utensil,s, and woodwork in the oyster house be scrubbed thor­
oughly with water and then washed with the formaldehyde solution,
The washing should be done in the fall. before any oysters are
brought in. The bins. benches, tubs, etc., should also be washed
several times during the winter whenever convenient.
When oysters are'taken from the water they immediately come in
contact with the deck of the boat, which is probably .infected with the
pink yeast. Oysters are usually placed in tubs, wheelbarrows, or bins
chat may also be contaminated. During shucking, the oysters become
infected with the yeasts from the shells. These yeasts are not easily
.1
.68
TECHNICAL BULLETIN 64, U. S. DEPT. OF AGRlCULTURE
removed ,by the washing process, and .are carried, with the oysters, '
into .the shIpping container, where they develop and produce the pink
,color, even though refrigerated.
Pinkleastsare distributed rather widely in nature and are to be
expecte in places like oyster bins where dust and dirt may remain
undisturbed during the summer. Thorough cleansing of the wood­
work with a liberal use of formaldehyde solution, however, should
remove the cause of the trouble.
Cultures of the yeasts isolated from pink oysters were found to
be nonpll-thogenic to laboratory animals. There ,if.: no reason to be­
lieve tha.t these yeasts would render shucked oysters injurious. The
quality of shucked oysters, with r£!spectto decomposition or possible
danger to health, must be jud~ed by criteria other than the presence
of a red or :pink color. In otner words, this color is not a criterion
of decomposItion. Oystersexhibit,ing it mayor may not be of proper
snnitaryquality. As the pink color does not appear until several
days after shucking, however, it must be assumed that other micro­
organisms have also developed in the oysters .,and that by the time
the oysters have become pink they are no longer pedectly fresh. The
uJ>pearance of the pink color indicates that several days have elapsed
SIDce shucking and that the oysters are approaching a cond.ition in
which they may be considered somewhat stale.. Although pink oys- ~
tel'S are harmleSs when eaten and may be edible, they should bel
examined carefully for evidence of decomposition before being sold
or et"ten.
Several investigators recently have suggested that there may be
another type of pink oysters which owe their .color to some agent
other than the pink yeast. The development of a pink color in
shucked oysters stored at 0° C. and the inability of certain inves­
tigators to reproduce the color by inoculation with pink yeasts iso­
lated from the pl'oduct under examination led to the suggestion that
some :purely chemical reaction may take place in oysters .as It result
of whIch a pink color is produced. At the present time there is no
proof of such a phenomenon, hut it is not improbable that such may
be the case. If future investigations show that a pink color can be
produced in oysters without the action of microorganisms, new
methods of control and prevention must be developed. In establish­
ments where the control measures here recommended have been
applied, however, trouble from pink oysters has ceased.
OLYMPIA OYSTERS
Only one outbreak of typhoid fever has been traced to the con­
sumption of the small native oysters produced .on the Pacific coast (14) . Following a Thanksgiving Day dinner where oyster cocktails were served in a restaurant at San Diego, Calif., many cases of typhoid fever were reported. Investigation indicated that polluted oysters from some small beds in San Diego Bay were used at the dmner. It was stated that "the acute symptoms in the outbreak under consideration were due to oysters having been improperly stored while infected with sewage organisms, and that spoilage per­ mitted of a rapid increase in certain of the bacteria contained." No BAOTERIOLOGY AND OHEMISTBY OF OYSTERS
69
case of illness has yet been reported from the consumption of the
Olympia oysters produced in the Pacific Northwest.
No speCIal bacteriological method for the examination of these
small oysters has been developed. The present standard metJlOds are
hardly applicable, as the Olympia oysters are too small to produce
enou~h lIquor for the test when only 5 to 12 oysters are used. If a
suffiCIently large number of such oysters are used in .order to obtain
the shell liquor necessary for the in<~culations there is no reason why
the standard procredurc should not be followed from that point and
the same standards of sanitary quality applied.
Sewage pollution of the oyster beds in the Pacific Northwest has
not been a serious factor. The bays in which these oysters are pro­
duced are usually fairly remote from centers of popUlation and no
large sewers empty into the near-by waters. The Japanese work­
men employed to care f.or oysters and to harvest them usuall'y live
in houseb.oats mODred .on or near the oyster beds. At one time it
was {Ollild that waste from these dwellings was polluting the oystert3
and steps were taken tD prDvide suitable means of waste dispDsal.
OccasiDnal repDrts recehred indicat~ various SDurces of pollutiDn of
the oyster beds, but the volume .of sewage in no case has been great
and remedial measures have been taken. Very little work, if any,
has been done upDn the bacterial flDra of the Olympia oyster. The
statements regarding sanitary surveys and the prDper conditions for
the grDwing of oysters (pp. 23-26) are just as applicable to Olympia
oysters as to the eastern oysters.
Studies .on the hibernation and self-purificatiDn .of the Olympia
oyster have nDt been reJ?orted and no information is available on
these questions. There IS no reason why Olympia oysters should
not function to rid themselves of polluting material in the same man­
ner as do eastern oyster·s.
rrhe requirements for sanitation within the shucking house and for
proper c.onditions during shipment apply to Olympia oysters just
as to eastern oysters, so far as the different methods of handling and
shipping permit of such requirements. The oyster-shucking houses
in and. about Olympia and other northwestern cities are small and
conditions can not be compared to those in the shucking houses of
the Atlantic and Gulf coasts. The oysters are received in clothsac~
and are handled in comparatively s'mall quantities.
The problems of green oysters and pink oysters have not yet
arisen in the native Pacific coast industry. In fact, this small oyster
industry of the Pacific coast has been comparatively free from many
of the troublesome problems affecting the eastern Gulf coast in­
dustries. As the territory surroundin~ the oyster-producing regions
becomes more thickly populated problems of poll uti .on with sewage
and trade wastes will be encountered but, profiting by the experience
gained on the Atlantic coast, oyster gr.owers and the State, Federal,
and municipal auth.orities may take whatever acti.on is necessary to
preserve the industry.
70 TECHNICAL BULLETIN 64, U. S. DEPT. OF AGBIOJJLTURE
):.ITERATURE CIT·ED
(1) ANONYMOUS.
1003.
,rHE OHEUISTRY ~F THE OYSTER.
PharIil. Jour. {SeI:.
4,
(2)
1903. OYSTERS AND
1903: 451.
ENTERIC FEVEI~ IN NElW ZEALAND.
v: 16)
70 :46.
Brit. Med. Jour.
(3) AMERIOANPUBLIC HEALTH ASSOCIATION.
1911.
'pRELIMIN~Y REPORT OF THE CmO!lTTEE ON STANDARD METHODS OF
SHELL-FISH EXAMINATION.
Amer. Jour. Pub. Health
1: 575-581.
(4)
1912. SEcOND
I'ROGRESS REPOIlT OF THE CO~[MITTEE ON STANDAIID ME'fHODS OF
Amer. Jour. Pub. Health ,2: 34-42.
SHELL~'lSH EXA~[lNATION.
(5)
1022. llEPOllT
OF COMMITTEE ON STANDAIlD METHODS FOIl THE llACTEnIOLOG­
ICM, E.,\,:AMINATION OF SHELLFISH. Amer. Jour. Pub. Health 12:
574-576.
(6)
1023. S'l"A"D,\Ill) METHODS FOR THE EXAMINATION OF
Ed. 5, rev., I11p., illus. New York, N. Y.
WATER AND SEWAGE.
(7) ASSOCIATION OF OFFICIAL AGRICULTUllAL CHEUISTS.
1025. Ok'FICIAL
(8)
AND TENTATIVE METHODS OF ANALYSIS. COMPILED BY THE
COMMITTEE ON ElUTING METHODS OF ANALYSIS. REVISED TO JULY:
I, 1024. Ed. 2, 535 p., Ulus. WaShington, D. C.
ATI,ANTIO CITY ACADEMY OF MEDICINE.
1002. REPOIlT ON 'n'l'HOID FEVER AT ATLANTIC CITY. Phila. Med. dOliI'. 10:
634-635.
(0) ATWATER, W. O.
1887.
THE OHE1>USTllY OF "OYBTEB-FATTENING."
Pop. Sci. Mo.
32: 76-87.
(10)
1887. THE
CHEMICAL CHANGES IN OYSTERS BY FLOATING.
Stream 29: 368-360.
Forest and
(11)
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CJIEMIOAL CHANGES PllODUOED IN OYSTERS IN FLOATING, AND
THEIR EFFEC'l' UPON THE NUTRITIVE VALUE. Amer. 'Jj'isheries Soc.
Trans. 16: 37-52.
(12)
1802. THE
(13)
(14)
(1.5)
CHEUICAL COMPOSl'flON AND NUTRITIVE VALUES OF FOOD-FISHES
AND AQUATIO INVEJl.TEBllATES.
U. S. Comn. Fish and Fisheries
Rpt. 1888: 670-868, illus.
- - - a n d WOODS, C. D.
1896. THE OHEMIOAL COMPOSITION OF AMERICAN FOOD MATERIALS. U. S.
Dept. Agr. Off. Expt. StaB. Bul. 28, 47 p., illus.
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1027. TYPHOlJJ FEVER TRACED TO POLLUTED OYSTERS. Calif. State Bd. Health
lUo. Bul. 12 (9) : 140-143.
BATES, C,
1916. THE HANDLING OF SHUOKED OYSTERS. Amer. Jour. Pub. Health 6:
987-090.
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1916. A COll(P~ISON
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(18)
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A.
OF BACTERIOLOGICAL 1o[ETHODS FOIl THE EXAMINATION
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1895. A NOTE ON THE TRANSMISSION OF THE INFECTION .OF TYPHOID FEVER
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1916. AN OUTllREAK OF TYPHOID ATTRIBUTED TO INFECTED OYSTERS. Jour.
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1896. ZUll OASUlSTIK DEll FISOHYEllGIFTUNG. Wiener KUn. Wchnschr. 9:.
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(20) BULSTllODE, H. T.
1904. REPORT UPON
ALLEGED OYSTER-BORNE ENTERIC FEVER _O\ND OTHER
ILLNESS FOLLOWING THE MAYOllAI, BANQUETS AT WINOHESTER AND
SOUTHAMPTON, AND UPON ENTERIC FEVER OCOUllRING SIMULTANE­
OUSLY ELSEWHERF" AND ALSO "\SCRIBED TO OYSTERS.
[Gt. Brit.]
Local GOYt. Bd. Ann. Rpt. (1902/03) 32 (sup.): 120-189, illus.
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1921. HYPOOHLORITE Pl\OfJESS OF OYSTER PURIFIOA"rION. Pub. Health
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(24) CASEY, E.
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190G. STUDIES AT TIlE I,A WRENCE EXPElIIMENT STATION ON THE POLLU­
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1917. THE COLORIMETRIC DETERMINATION OF HYDIIOGEN ION CONCENTRaTION
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AND ITS Al'I~LICATIONS IN BACTERIOLOGY.
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1895. THE OUTllllEAK OF TYPHOID FEVER AT WESLEYAN UNIVERSITY. Conn.
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1916. INVESTIGATION OF THE POLLUTION AND SANITARY CONDITIONS OF THE
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1895. TYPHOID FEVER AND OYSTERS AND OTHER MOLLUSOS. Brit. Med. Jour.
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1904. TYPHOID FEVER AND OYSTERS. (Abstract) Med. News 85: 511.
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1896. A BACTERIOLOGIC STUDY OF OYSTERS, WITH SPECIAL REFEBENOE TO
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1905. THE DISTRIBUTION OF SEWAGE IN THE WATERS OF NARRAGANSETT BAY,
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1903. NOTE ON THE ABBENCm Oli' B. COLI, &Te., FROM THIC NORKAL OYSTJIB.
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73
"
80~OALLED .. FA'l'TENING"
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FISHERIES OP MAIIYLAND AIID VIIIGINIA, 1920.
Bm. Fisheries Statis. Bul. 520, 1 p.
[1923].
FISHERIES OF NEW YOnK, NEW JERSEY, PENNSYLVANIA, AND DELA­
WAllE, 1021. U. S. Dept. Com., Bur. Fisheries Statis. Bul.
(94) 569, 1 p.
(95)
[1925). FISHERIES O~·
.~.; PACIFIC CG'AST STATES, 1922.
Bur. Fish~ .. t!s Statis. Bul. 647, 1 p.
(96)
[1925]. FISHERIES
U. S. Dept. Com.,
OF THE SOUTH ATLA:'iTIO STATES, 1923.
Com., Bur. Fisheries Statis. Bul. 652, 1 p.
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Bul. 657, 1 p.
[1925J. FISHERIES
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Fisheries Statis. Bul. 670, 1 p.
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Pub. Health Rpts. [D. S.] 40: 693-722, illus.
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31: 1848-1852.
1916..PURIFYING
(103)
OYSTERS BY USE OF CHLORINE IN .. FLOATING" WATF.R.
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1920. THE
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Jour. PIli>. Health 10: 342-344.
ArneI'.
,\
BACTERIOLOGY AND CHEMISTRY OF OYSTERS
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75
WELLS,
OYSTER PURIFICATION PLANT.
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(lOG)
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PURIFIED OYSTERS.
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G. E.C.
1800. SPEOlAL BEPOR't
WOOD,
TO THE "BRITISH MEDICAL JOURNAL" ON THE cm­
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VEYED.BY SHELLFISH WITH SPECIAL REFERENOE TO OYSTERS. Brit.
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ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE lIfareb 14, 11%1
Secretary of Agriculture___________________ W. M. JARDINE.
A8si8tant Secretary _______________________ R. W. DUNLAP. Director of Scientific Work ____________ - ___ A, F. WOODS. Director of Regulatory Work _______________ WALTERG. CAMPBELL. Director of ExtenBion __________________ .__ C. W.WARBURTON. Director of Peraonnel and Business Admin­
istration ______________________________ W. W. STOCKBERGER. Director of Information___________________ NELSON ANTRIM CRAWFORD. Solicitor ________________________________ R. W. WILLIAMS.
Weather Bureau________________________._ CHARLES F. MARVIN, Chief.
Bureau of Animal Indu8try ____ ~ __________ JOHN R. MOHLER, Chief.
B1lreau of Dairy Indll.stry _________________ L. A. ROGERS, Acting Chief.
Bureau of Plant Industry ___ - _____________ WILLIAM A. TAYLOR, Chief.
Forest Service ___________________________ W. B. GREELEY,Chief.
Bureau of Chemistry and Soils ____________ H. G. KNIGHT, Chief.
Bureau of Entomology ____________________ C. L. MARLATT, Chief. Bureau of Biological Survey _______________ PAUL G. REDINGTON, Chief. B'ureau of Public Roads __________________ THOMAS H. MACDONALD, Chief. Bureau of Agricultural Economics __________ LLOYD S. TENNY, Chief. Burea'u of Home Economics _______________ LOUISE STANLEY, Chief. Federal Hort'icult'ural Board _______________ C. L. MARLATT, Chairman.
Grain Futures Administration _____________ J. W. T. DUVEL, Chief.
Food, Drug, and Tnsecticide Administration_ WALTER G. CAMPBELL, Director aJ
Regulatory Work, in Charge.
Office of Experiment Station8- _____________ E. W. ALLEN, Chief.
Ojlice of Cooperative Extension Work ________ C. B. SMITH, Chief. Library ________________________________ CLARIBEL R. BARNETT, Librarian. This bull~'tin is a joint contribution from
Bureau of Chemistry and So·ils ___________._ H. G. KNIGHT, Chief.
Chemical and Technological Research ___ C. A. BROWNE, Chief.
Food, Drug, and Insecticide Administration __ WALTEC G. CAMPBELL, Director of
Regulatory Work, in Charge.
Food ControL ______________________ R. W. BALCOM, Senior Chemist, in
Charge.
76
ADDITIONAL COPIES 0;- TillS Pt:'IILICATION MAY BE PROCURED FROM TIl}) SUPERINTENDENT OF DOCUMENTS U.S.GOVERN)! ENT PRINTING OFFICI: WASIIINGTON, D. C, AT Ii CENTS PER COPY "V
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