APPuED MICROBOLOGY, May 1970, p. 734-741Copyright © 1970 American Society for Microbiology

Bacteriological and Shelf-Life Characteristics ofCanned, Pasteurized Crab Cake Mix

PAISAN LOAHARANU' AND ANTHONY LOPEZDepartment of Food Science and Technology, Virginia Polytechnic Institute, Blacksburg, Virginia 24061

Received for publication 6 March 1970

The bacteriological spoilage characteristics of a canned, pasteurized crab cake mixproduct stored at various temperatures were investigated. A large number ofbacteria, both mesophilic and psychrophilic, survived the pasteurization process.Bacillus and Micrococcus were found to predominate when the product was storedat 30 C (86 F) and 18 C (64 F), whereas Alcaligenes predominated at 2 C (36 F).The product was found to be free of Escherichia coli. Bacterial counts, trimethyl-amine nitrogen, volatile reducing substances, and ammonia determinations wereevaluated as indices of quality for the product. Close correlation was observedbetween bacterial counts, volatile reducing substance values, and organoleptictests when the product was stored at 30 C (86 F). The shelf-life of the product wasapproximately 6 months at 2 C (36 F), 4 days at 18 C (64 F), and 27 hr at 30 C(86 F).

Canned, pasteurized crab cake mix is a rela-tively new product. There is little available in-formation concerning its shelf-life and spoilagecharacteristics. The crab cake mix is commer-cially prepared by mixing crab meat with otheringredients, such as bread crumbs, eggs, mayon-naise, and other flavoring substances. The formulafor the crab cake mix product is shown in Table1. The product is packed at atmospheric pressurein 307 X 409 C enameled cans of 1 lb (454 g) netproduct capacity, pasteurized in a water bath at85 to 87 C (185 to 190 F) for 110 min, and imme-diately cooled. The product is then kept at 0 to5 C (32 to 41 F).A problem may arise when the consumer re-

moves the product from cold storage in a foodstore. In some instances, it may take several hoursbefore the product is returned to a refrigerator inthe consumer's home, or the product might inad-vertently be left unrefrigerated overnight. Bac-teriological changes occur during this period,some of which are undesirable from the stand-point of product quality, and perhaps safety. Thisproblem is of interest to consumers and the in-dustry.

Bacteriological spoilage of crab meat has beenstudied by Harris (15), Alford et al. (1), andBenarde (6). Pasteurization of crab meat in metalcontainers was first investigated by Tobin andMcCleskey (27). They packed and pasteurized

Present address: Office of Atom-iic Energy for Peace, Bangkhen,Bangkok, Thailand.

crab meat at 15 psi for 5, 10, and 15 min. They re-ported that slight discoloration of the surface ofthe pasteurized meat was observed.

Pasteurization of crab meat packed in cans in awater bath at the temperature below the boilingpoint of water was studied by Anzulovic andReedy (4) and by Flynn and Tatro (14). Theseinvestigators found that pasteurization killed alarge number of microorganisms includingEscherichia coli, and that pasteurization pro-longed the keeping quality of crab meat for a con-siderable time.Much research has been done by employing

trimethylamine nitrogen (TMA-N) as an indexof decomposition of marine fish and shellfish.Spinelli et al. (25) studied the relation of bacterialcounts and increase in TMA-N with sensoryevaluation in vacuum-packed king crab meat.They found that samples with TMA-N contentexceeding 1.0 mg/100 g received a poor rating.There appeared to be a fair correlation betweenincrease in bacterial counts, TMA-N content,and a decrease in sensory scores. Farber (12)claimed that the content of TMA-N was not asensitive, reliable, or reproducible index of fishspoilage. Either the increase in TMA-N occurredduring the latter stage of spoilage, or there was avariation in levels between species, or no appre-ciable increase took place. Volatile reducing sub-stances (VRS) content has been found to be a

useful index of freshness of fresh and cannedfishery products, as indicated by Farber (11),

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CHARACTERISTICS OF CANNED CRAB CAKE MIX

TABLE 1. Formula for 100 lb (45 kg) of crabcake mix

Crab meat (claw 70%,regular 30%) ......... 72 lb (32 kg)

Mayonnaise ............ 10 lb (4.5 kg)Bread crumbs.. 8.5 lb (3.8 kg)Eggs................... 8.5 lb (3.8 kg)Mustard................ 6 oz (170 g)Pepper ............... 6 oz (170 g)Spice mix.............. 2.5 oz (71 g)Dry onion flakes. 1.5 oz (42.5 g)

and Farber and Ferro (13). The content of VRSwas reported to correlate closely with organo-leptic judgments. Burnett (8) devised a colori-metric method which used ammonia as an indexof decomposition in fresh and frozen crab meat.This method is based upon the color reactionbetween ammonia, thymol, and bromine. Theauthor reported that ammonia content increaseduniformly and rapidly with spoilage, and thatammonia could be detected before spoilage wasdetected organoleptically.

In crab cake mix there are ingredients of widelyvariable microbiological quality. The pasteurizedproduct, therefore, is expected to have a variablespoilage pattern different from that of crab meator fish. Generally accepted objective tests forascertaining degree of spoilage of crab meat orfish may not be adequate for crab cake mix.The principal objectives of this investigation

were: (i) to determine the shelf-life of the productat various temperatures by studying the bacterio-logical spoilage pattern through bacterial countsand characterization of the more prevalent bac-teria in the product; (ii) to evaluate some of theexisting objective tests as indices of quality anddegree of spoilage of the crab cake mix; and (iii)to determine the correlation between odor andbacterial count, TMA content, VRS value, andamount of ammonia present in the product.

MATERIALS AND METHODSRate of heat penetration in canned crab cake mix

was determined under commercial conditions. Themethod described by Alstrand and Ecklund (2) wasused. Six 307 X 409 cans of 1 lb (454 g) net productcapacity were used for the determination. The moldedbakelite thermocouples were first placed at the geo-metrical centers of the test cans before filling. Fillingwas done in such a way that the thermocouple tipswere imbedded in the product with no air spacearound them. The canned product was pasteurized ina steam-heated water bath, previously heated to 85 C(185 F), for 110 min. Center can temperatures of theproduct were read before the beginning of the pas-teurization process and every 10 min throughout theheating and during the cooling operation, until thetemperature returned to 60 C (140 F). A Brown po-

tentiometer with automatic junction compensationwas used to make temperature readings.The general plate count techniques were those out-

lined in Standard Methods for the Examination ofDairy Products (3). Throughout this study, BBL stand-ard plate count (SPC) agar was used for plate counts.For estimating bacterial population in fresh crabmeat and crab cake mix, SPC agar was dissolved inartificial sea water (24).

Total plate counts of crab cake mix ingredients weredetermined. Samples of ingredients used for crab cakemix were obtained from a crab processing plant,placed aseptically in sterile bottles, and transportedin ice to a laboratory where plate counts were madeimmediately. One gram of each of the ingredients wasmixed with 9 ml of sterile water; the samples werefurther diluted and plated on SPC agar medium. Allplates were prepared in triplicate and incubated ateither 30 C (86 F), 18 C (64 F), or 2 C (36 F) to de-termine the microflora growing in the samples at eachof three temperatures. Plates were incubated at 30 C(86 F) for 48 hr, at 18 C (64 F) for 4 days, and at 2 C(36 F) for 18 to 20 days before counting was made.The bacteriological spoilage pattern of the product

was studied at 30 C (86 F) to represent the upper ex-tremes of room temperature storage, at 18 C (64 F) toinclude a temperature intermediate between room andrefrigerated storage temperatures, and at 2 C (36 F) toduplicate refrigerated storage temperature.The more prevalent colonies of bacteria that grew

on plates incubated at the three temperatures were iso-lated and differentiated according to genera. Routinecharacterization tests were done according to Bergey'sManual of Determinative Bacteriology (7) and Guideto the Identification of the Genera of Bacteria (23).Flagella were stained by using the method of Leifson[E. Leifson, J. Bacteriol. 36:656 (Abstr.), 1938]. Oxi-dase activity was determined by the method of Kovacs(17).Chemical analysis of the pasteurized crab cake mix

for moisture, crude fat, protein, and ash were per-formed in accordance with Association of OfficialAgricultural Chemists techniques (16).TMA-N content of pasteurized crab cake mix was

determined colorimetrically as trimethylamine picrateby the method of Dyer (10). A Spectronic 20 (Bausch& Lomb) colorimeter was used. TMA-N values wereread as percentage of transmittance from the TMA-Nstandard curve.VRS values were determined by the method ofLang

et al. (18). The apparatus was slightly modified. It wasfound that simple test tubes (20 by 125 mm) could beused as sample vessels, since foaming was eliminatedby using Antifoam A (Dow Chemical Co.). For eachdetermination, 10 g of pasteurized crab cake mix, di-luted 1:1 with distilled water, was weighed into anaeration vessel to which a few drops of the siliconeantifoaming agent was added. Exactly 50 ml of 0.02 NKMnO4 in 1.0 N NaOH solution was pipetted into areaction flask. The determination of VRS values wascarried out at room temperature. Room air was drawninto the VRS apparatus at a rate of 100 liter/hr bymeans of a vacuum pump. The sample was aerated for40 min. An air blank was also determined by using 10

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736 LOAHARANU AND LOPEZ

IL 0-0 CENTER CAN TEMP|t-180L°

170

"I

40 60 80 100 120 140

TIME (MIN)

FIG. 1. Heat penetration curve for crab cake mix in307 X 409 cans with thermocouples at geometricalcenter ofcan.

ml of emulsified redistilled water, prepared by blend-ing a few drops of the silicone antifoaming agent in 100ml of redistilled water, in place of the sample.

At the end of the aeration period, the reaction flaskwas removed. A 25-ml amount of 6 N H2S04 and 15ml of 20% KI in 0.1% Na2CO3 were added. Theliberated iodine was titrated with 0.025 N Na2S2O3 in0.2% Na2CO, and 0.1% Na2B4O7. 10 HaO solution.Toward the end of the titration, several drops of 1%soluble starch in saturated NaCl solution was addedas an indicator. VRS value in the sample was calcu-lated by the equation: VRS value = titration -sam-ple titration X normality Na2S2O3 X 1000/weight ofsample in grams.The VRS value determined as described above was

expressed in microequivalent GuEq) of KMnO4 pergram of sample.Ammonia content in the product was determined

by the method of Burnett (8).Odor of pasteurized crab cake mix, stored at room

temperature for various periods of time, was evalu-ated by a panel of 20 persons. The panel was untrainedbut was made familiar with the product. A nine-pointhedonic scale was used in rating the sample. Odorevaluations were made by using four replicates.

RESULTS

The rate of heat penetration in crab cake mixcommercially packed in 307 X 409 C enameledcans is shown in Fig. 1. Approximately 100 minwas required for the center can temperature toreach 82 C (180 F), the desired temperature forpasteurization. The center can temperature wasmaintained at 82 C (180 F) for approximately 10min before the cans were cooled.The pasteurization process at 85 to 88 C (185

to 190 F) for 110m- reduced the bacterialcounts in the product by a factor of approxi-mately 20, from 6.0 X 105 to approximately 3.3 X104 per g.

Total plate counts of microorganisms in freshcrab meat and in other ingredients used for pre-

APPL. MICRoBIoL.

paring crab cake mix are shown in Table 2.Bread crumbs showed fairly large counts of bothmesophilic and psychrophilic bacteria, whereaspepper and spice mix contained rather largenumbers of only mesophilic bacteria. A largenumber of both mesophilic and psychrophilicbacteria were found in raw crab cake mix.

Bacterial counts of the product stored at 30 C(86 F) are shown in Fig. 2. Bacterial counts fromplates incubated at 30 C (86 F) and 18 C (64 F)increased with storage time, as might be expected.The increase in number of bacteria indicates

TABLE 2. Total plate counts for microorganisms iningredients used for crab cake mix

Incubation temp (C)aIngredient

2 18 30

Regular meat. . . 3.4 X 104 4.1 X 104 4.5 X 104Claw meat...... 1.5 X 105 3.1 X 105 4.1 X 105Pepper.......... <300 1.5 X 108 2.0 X 108Spice mix....... <300 1.2 X 106 0.9 X 106Bread crumbs... 2.6 X 105 2.4 X 106 2.0 X 106Dry onion

flakes......... <300 2.1 X 104 2.9 X 104Mayonnaise ..... <300 <300 <300Mustard ........ <300 <300 < 300Raw crab cakemix......... 2.4 X 106 3.4 X 1066.0 X 106

a Results expressed asgram.

I07

'210 _

a-

I-,

4 X2s le00

LUJm32 10pz I

microorganisms per

0 8 16 24 32 40 48

PRODUCT STORAGE TIME AT 30° C (HOURS)

FIG. 2. Bacterial counts for pasterurized crab cakemix stored at 30 C (86 F).

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CHARACTERISTICS OF CANNED CRAB CAKE MIX

w 00-

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- O-0 301,CF 4/ °° ~~~~~~~~18-C

go [0Y-U 2-CC1040

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PRODUCT STORAGE TIME AT 180C (DAYS)

FiG. 3. Bacterial counts for pasteurized crab cakemix stored at 18 C (64 F).

typical growth curves which clearly show lag,log, and stationary phases. The product con-tained approximately 2 X 104 bacteria per g atzero storage time. The counts increased signifi-cantly after approximately 10 to 12 hr of storagetime at 30 C. This can be explained by the factthat the rate of heat penetration in the product isslow. After 24 hr, the product showed a sign ofslight spoilage, as observed by odor. Bacterialcounts showed approximately 108 organismsper g. This indicates that the shelf-life of theproduct stored at 30 C (86 F) is in the neighbor-hood of 24 hr. When plates were incubated at2 C (36 F), the number of bacteria, presumablypsychrophiles, increased slightly up to approxi-mately 12 hr of storage time at 30 C (86 F) anddeclined significantly thereafter. The increase innumber of bacteria at the beginning indicatedthat the temperatures in the can of crab cake mixwere suitable for psychrophilic bacteria to growup to approximately 12 hr of storage time. Therapid decrease in the number of bacteria after 12hr of storage is postulated to be due to the geneticbehavior of the psychrophiles in the product.These psychrophiles presumably came from a coldmarine environment in the Chesapeake Bay area.When exposed to high storage temperatures, theytended to die.

Bacterial counts in the product stored at 18 C(64 F) for various lengths of time are shown inFig. 3. When plates were incubated at each of thethree incubation temperatures, both mesophilicand psychrophilic bacteria appeared to grow well.This is due to the fact that the storage tempera-ture of 18 C (64 F) is within the growing rangesof both types of bacteria. However, the meso-

philes seemed to grow better than the psychro-philes after 2 days of storage. After 4 days ofstorage at 18 C (64 F), an off odor was noted inthe product. Bacterial count at this time showedapproximately 7 X 107 organisms per g.

Bacterial counts of the product stored at 2 C(36 F) were made at 1-month intervals for 6months (Fig. 4). It was observed that the countsof both mesophilic and psychrophilic bacteriawere fairly low, even after 6 months of storagetime. A slight off odor was observed at the end ofthat period, but the product was still consideredacceptable. The shelf-life of the product at 2 C(36 F) was considered to be 6 months.The next step in the bacteriological examina-

tion of pasteurized crab cake mix was to charac-terize bacteria isolated from the product stored atdifferent temperatures. Attempts were made tocharacterize the more prevalent bacteria in theproduct stored at the three temperatures, namely,30 C (86 F), 18 C (64 F), and 2 C (36 F). Threegenera of bacteria were found to be prominent inpasteurized crab cake mix stored at the three tem-peratures (Table 3). They were Bacillus, Micro-coccus, and Alcaligenes. Bacillus was charac-terized mainly according to its ability to survivethe heat treatment of 65 C (149 F) for 30 min,and as catalase-positive, gram-positive, aerobic,spore-forming bacilli. Micrococcus was charac-terized mainly as gram-positive cocci in clumps,for producing acid from glucose oxidatively, andfor having the ability to survive the heat treat-ment. Alcaligenes was characterized as gram-negative and oxidase-positive, for being motilewith peritrichous flagella, for its inability toutilize carbohydrates, and for its ropy colonies.Attempts were made to detect E. coli in pas-

cr id0CO INCUBATION TEMPcr 0-0 30-0C

LL0

0 2 3 4 5 6

PRODUCT STORAGE TIME AT 20 C (MONTHS)

FIG. 4. Bacterial counts for pasteurized crab cakemix stored at 2 C (36 F) for 6 months.

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LOAHARANU AND LOPEZ

TABLE 3. Characterization ofthe more prevalentbacteria isolatedfrom commercially prepared, pasteurizedcrab cake mixa

Characteristics Bacillus Micrococcus Alcaligenes

Morphology................................. Straight rod Cocci, in clump Straight rodGrowth in air ................ + + +Optimal growth temp (C) ........... 30 30 18Gram reaction ................ G+ G+ G-Glucose reaction .............. A AAcid from glucose

Oxidative ................. + +Fermentative ...............

Sucrose reaction ............... A ALactose reaction ...............

Litmus milk reaction ................ Proteolysis Proteolysis Slight proteolysisCatalase reaction ............................ + + +Survived heat treatment (65 C for 30 min) ...... + +Spore stain.................................. + NA NAMotility................................... + NA +Flagella stain ................. NA NA PeritrichousOxidase activity ................ NA NA +Gelatin reaction .................. Liquefaction - NA

a + Positive reaction; -, negative reaction; G+, gram-positive; G-, gram-negative; A, acid produc-tion; NA, test does not apply.

TABLE 4. pH values" of pasteurized crab cake mixstored at 30 C (86 F), 18 C (64 F), and 2 C

(36 F)

30 C (86 F) 18 C (64 F) storage 2 C (36 F) storagestorage

Storage ~ Storage StorageStoerage) pH time pH timne pHtime(hr) ~(days) (days)

0 7.22 0 7.22 0 7.224 7.10 0.5 7.12 4 7.208 7.18 1 7.10 8 7.1012 7.12 2 7.17 12 7.2024 7.10 3 7.10 16 5.1748 6.50 4 6.90 20 7.10

a Mean values from three determinations.

teurized crab cake mix. Samples of the product,with appropriate dilutions, were inoculated intolactose broth and incubated at 35 C (95 F) for24 to 48 hr for presumptive test. No evidence ofgas production was observed after 48 hr of incu-bation. This indicates that the product was freefrom E. coli.The pH values of samples of pasteurized crab

cake mix stored at 30 C (86 F), 18 C (64 F), and2 C (36 F) are shown in Table 4. Determinationsof pH in the product at each storage temperatureindicate that, although pH of the samples inadvanced stages of spoilage showed a lower valuethan that of fresh samples, the samples in betweeninhibited a nonuniform decrease of pH. No sig-

nificant difference was found in the pH of samplesin borderline stages of spoilage when comparedwith the pH of relatively fresh samples. There-fore, pH is not a reliable index of decompositionfor pasteurized crab cake mix.

Proximate composition data for pasteurizedcrab cake mix are presented in Table 5. Thequantity of crude fat in the product is relativelyhigh because a rather high proportion of mayon-naise is included in the formula.TMA-N content of pasteurized crab cake mix

stored at 30 C (86 F) for various periods of timeis shown in Fig. 5. It is evident that TMA-Ncontent increased significantly after approxi-mately 24 hr of storage, or when the product wasapproaching an advanced stage of spoilage. Nosignificant difference was found in TMA-Ncontent of the product stored at zero time, 6, 12,and 24 hr. These results show that TMA-N is

TABLE 5. Proximate composition of pasteurizedcrab cake mix

Carbo-Determi- MosueProtein hydratesnation Moisture (N X Fat Ash (by

6.25) differ-ence)

% % ~% % %xa 68.37 14.58 10.04 2.95 4.06Sb 0.22 0.61 0.24 0.08

a Mean value from 10 determinations.b Standard deviation.

738 APPL. MICROBIOL.

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CHARACTERISTICS OF CANNED CRAB CAKE MIX

90s ,3

80 F '470 ic?

60-a.5V 50

a:t> 40

30

2

4Ir-

0

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20F

10 L 10 L I.0 6 12 18 24 30 36

PRODUCT STORAGE TIME AT 300C(HOURS)

FiG. 5. Comparison of bacterial counts, trimethyl-amine nitrogen (TMA-N), volatile reducing substances(VRS), and odor evaluation of pasteurized crab cakemix stored at 30 C (86 F).

not a sensitive test for quality of pasteurized crabcake mix at an early stage of deterioration. Theresults appear to agree with those obtained byBailey et al. (5), Shewan and Jones (22), andothers.

Figure 5 also shows the VRS values of pas-teurized crab cake mix stored at 30 C (86 F) forvarious lengths of time. It was observed that theVRS values increased progressively with an in-crease in storage time. The product showed VRSvalues of 25.85 ,uEq per g at zero storage time,which increased progressively with storage time.There was no significant difference in VRS valuesof samples stored for 0, 6, and 12 hr. VRS valuesincreased significantly after 12 hr of storage at86 F. The VRS value of the product at 24 hr ofstorage was not only significantly different fromthat at 12 hr of storage, but also significantlydifferent from the product after 30 hr of storage.At 24 hr of storage, the product appeared to havea VRS value of 34.65 ,uEq per g and was stillconsidered acceptable by the panel of judges.However, at 30 hr of storage, the VRS value ofthe product was 43.47 jAEq per g, and the productwas considered unacceptable.The average odor scores for the product stored

at 30 C (86 F) are also presented in Fig. 5. Therewas no significant difference between zero ex-

posure and exposure to 30 C (86 F) for 6 hr. Theproduct exposed for 12 hr at 30 C (86 F) showed

no significant difference from that with zeroexposure. The product exposed to 30 C for 24 hrwas significantly different from any of the productexposed for shorter periods of time. This product,however, was also significantly different from theproduct exposed to 30 C for 30 hr which wasjudged unacceptable. This result indicates thatthe quality of pasteurized crab cake mix storedfor 24 hr at room temperature was approachingthe borderline stage of spoilage, although it wasstill considered acceptable. On the contrary, theproduct exposed to 30 C for 30 hr at room tem-perature was considered unacceptable. The bor-derline stage of spoilage, therefore, appeared tooccur between 24 and 30 hr of storage time andwas extrapolated to be approximately 27 hr at30 C (86 F).A recovery test was employed to determine the

efficiency of the colorimetric method used fordetecting amount of ammonia (NH3) in theproduct. It was found that the determination ofNH3 in the product was not reliable as a test forproduct quality, as the results were not repro-ducible. It was concluded that other substancesin the product were probably extracted alongwith NH3 and interfered with the colorimetricdetermination.On the basis of the results given above, shelf-

life of the product was approximately 27 hr at30 C (86 F), 4 days at 18 C (64 F), and 6 monthsat2C (36 F).

DISCUSSION

Bacterial counts have been used by manyinvestigators to follow the deterioration of fishand shellfish. In this study, the product imme-diately after pasteurization had total plate countsof approximately 3.5 X 105 per g. When theproduct was stored at 30 C (86 F), the count in-creased to approximately 108 at the time of spoil-age. The bacterial counts of the product stored at30 C appeared to correlate with the degree ofacceptability as indicated by odor. The bacterialcounts, therefore, appeared to be a good index ofspoilage of the product when stored at 30 C,as shown in Fig. 5. When the product was storedunder refrigeration, the increase in bacterialcounts showed no correlation with degree ofspoilage. Figure 4 shows that approximately 107bacteria per g were detected in the product heldrefrigerated [2 C (36 F)] for 6 months, whenplates were incubated at 2 C. The count wastypical for spoiled product exposed to room tem-perature, yet the product was still considered ac-ceptable. These results indicate that the type ofbacteria in the product is also important as anindex of spoilage. The storage temperature of the

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740 LOAHARANU AND LOPEZ

product and the incubation temperature of theplates appeared to be significant when using bac-terial count as an index of spoilage. A disad-vantage of using plate count as an index of spoil-age is the length of time involved in incubation.

Bacteriological spoilage of the product is con-siderably retarded if the product is held refrig-erated. Bacillus and Micrococcus showed optimalgrowth at 30 C (86 F). These bacteria are thenexpected to contribute very little to spoilage of theproduct at refrigerated storage temperatures.Alcaligenes, although showing optimal growth at18 C (64 F), can grow well at refrigerated storagetemperatures.Work done by Tobin et al. (26), Reay and

Shewan (20), Campbell and Williams (9), andothers indicated that the Pseudomonas-Achromo-bacter group of bacteria contributes significantlyto the spoilage of most fishery products held atrefrigerated storage temperatures. However, thisgroup of bacteria was not found in pasteurizedcrab cake mix, probably as the consequence ofsevere heat treatment during pasteurization. Thisresult agrees with that of Macaulay et al. (19),who reported that Alcaligenes had relativelyhigher heat resistance that the pseudomonads.No reports have been found in the literature indi-cating that Alcaligenes contributes significantlyto the spoilage of fishery products. In this study,Alcaligenes was found to be abundant in pas-teurized crab cake mix, but it did not appear tocontribute significantly to the spoilage of theproduct at refrigerated storage temperatures[2 C (36 F)]. Probably for this reason, theproduct was considered acceptable after a 6-month storage period.The TMA-N content in pasteurized crab cake

mix was found not to be a sensitive index of spoil-age of the product. The TMA-N content ap-peared to increase during the latter stages ofspoilage. Early changes in quality of the productcould not be detected by the TMA-N method.

Determination of the VRS value of pas-teurized crab cake mix can be carried out in lessthan 1 hr. The VRS values of the product werefound to increase with length of the storage time.A close correlation was observed between theVRS values and organoleptic judgments. Moresignificantly, quality changes in the product couldbe detected chemically by VRS values during theearly stages of decomposition. VRS values,therefore, appear to provide a sensitive andreliable measure of the quality of pasteurizedcrab cake mix.The determination of ammonia in the crab

cake mix product by a colorimetric method wasnot found reliable as an index of quality.

APPL. MICROBIOL.

Canned, pasteurized crab cake mix is preparedby mixing crab meat with other ingredients, someof which are heavily contaminated with micro-organisms, such as the spices. The product ispasteurized in a water bath at 85 to 88 C (185 to190 F) for 110 min. It is possible that Clostridiumbotulinum types A and B, which are common soilorganisms, and types E and F, which have beenisolated from fish and shellfish, may be present inthe product and survive the pasteurization proc-ess. Moreover, the condition of the product in thecan is favorable for growth of C. botulinum. Asthe product is a semisolid mass, anaerobic condi-tions could exist in it. C. botulinum type E isknown to grow and produce toxin after 1 monthof incubation at 38 F as reported by Schmidt et al.(21).To avoid the possibility of microbial growth

and toxin production, the product would have tobe stored at temperatures below 38 F. To preventphysicochemical changes caused by freezing, thestorage temperature should be higher than thefreezing temperature of any of the product com-ponents. Food storage temperatures in the rangeof about 28 to 38 F are rarely found in retailstores and homes. This presents a serious problemin marketing products like the one discussed here,and other similar meat and seafood productspacked in hermetically sealed containers but notgiven a heat treatment that results in commercialsterilization.

ACKNOWLEDGMENTS

We are indebted to F. W. Cooler, Associate Professor of FoodScience and Technology at Virginia Polytechnic Institute, forintroducing this problem and for helpful suggestions during thecourse of the work. Thanks are also due to C. Keyser and N.Keyser of Keyser Brothers, Inc., Lottsburg, Va., for supplyingsamples of the crab cake mix product and other materials used inthis investigation, and for their interest in this work.

LITERATURE CITED

1. Alford, J. A., L. Tobin, and C. S. McCleskey. 1941. Bacterialspoilage of ice fresh crab meat. Food Res. 7:353-359.

2. Alstrand, D. V., and 0. F. Ecklund. 1952. The mechanicsand interpretation of heat penetration tests in cannedfoods. Food Technol. 6:185-189.

3. American Public Health Association. 1960. Standard methodsfor the examination of dairy products. American PublicHealth Association, New York.

4. Anzulovic, J. V., and R. J. Reedy. 1942. Pasteurization of crabmeat. Fish. Market News 4:3-6.

5. Bailey, M. E., E. A. Fieger, and A. F. Novak b456. Objectivetests applicable to quality studies of icc stored shrimp.Food Res. 21:611-619.

6. Benarde, M. A. 1958. Observation on the spoilage of crabmeat. J. Milk Food Technol. 21:318-321.

7. Breed, R. S., E. G. D. Murray, and N. R. Smith. 1957. Bergey'smanual of determinative bacteriology, 7th ed. The Williams& Wilkins Co., Baltimore.

8. Burnett, J. L. 1965. Ammonia as an index of decompositionin crab meat. J. Ass. Offic. Anal. Chem. 48:624-627.

9. Campbell, L. L., Jr., and 0. B. Williams. 1952. The bacter-

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iology of Gulf Coast shrimp. IV. Bacteriological, chemicaland organoleptic changes with ice storage. Food Technol.6:125-126.

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741VOL. 19, 1970

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