Fishballs from six local factories were stored at 5°C for 1, 2, 3, 4, 7 and 10 d. There were no changes in texture at 3 d of storage but bacterial spoilage rendered the fishballs unacceptable by the fourth day. Most of the bacteria were non-halophilic. The main genera isolated were Aerococcus, Acinetobacter, Pseudomonas, Staphylococcus, Corynebacterium, Micrococcus, Streptococcus and Enterobacteria

Lee, C. C.

Yu, S. Y.

Universiti Putra Malaysia Institutional Repository

Asian Fisheries Science 8 (1995): 89-93.Asian Fisheries Society, Manila, PhilippinesEffect of Storage at SoC on the Bacterial Floraand Physical Properties of Malaysian FishballsS.Y.YU and C.C. LEEFaculty of Food and Science and BiotechnologyUniversiti Pertanian Malaysia43400 UPM Serdang, Selangor, MalaysiaAbstractFishballs from six local factories were stored at SoC for 1, 2, 3, 4, 7 and 10d. There were no changes in texture at 3 d of storage but bacterial spoilagerendered the fishballs unacceptable by the fourth day. Most of the bacteriawere non-halophilic. The main genera isolated were Aerococcus, Acinetobacter,Pseudomonas, Staphylococcus, Corynebacterium, Micrococcus, Streptococcusand Enterobacteria.IntroductionFishballs are a popular food in much of the Asian region. Made by mixingfish mince with starch, salt, sugar, monosodium glutamate and spices into aball-shaped dough, they are cooked to a gel which is consumed with rice,noodles or as a snack. They are usually sold in local wet markets, unchilledand with little or no packaging. Being a high moisture food (>80%), they arehighly perishable with a short shelf-life. Thus, data on their spoilage characteris-tics is necessary before monitoring and control systems can be implemented.This study reports the microbial and physical changes occurring in fishballsfrom six Malaysian factories during storage at SoC.Materials and MethodsRaw MaterialsFreshly produced fishballs were purchased from the six largest factories inKuala Lumpur. The samples were packed in aseptic plastic bags and trans-ported immediately to the laboratory. Upon arrival at the laboratory, the fishballswere transferred using aseptic forceps into sterile plastic bags (200 g per bag),sealed in a laminar-flow chamber, and stored at SoC. Samples were analyzed at0, 1, 2, 3, 4, 7 and 10 d of storage. Two samples from each factory were testedfor each parameter on each day except for the folding test, when five sampleswere tested.8990Physical TestsThe Folding and Teeth-Cutting Tests of Hasegawa (1987) were used. TheFolding Test measures resilience, and the Teeth-Cutting Test measures springi-ness of the fishballs. Samples were boiled for 5 minutes and then cooled toroom temperature (28°C) before testing.FOLDING TESTFive slices, each 5 mm thick and 20 mm in diameter, were cut from fivefishballs. Each was then folded in half and, if there was no tear or breakage,further folded into quarters. The grading was as follows: AA, no breakage in anyof five samples when folded in quarters; A, slight tear in anyone of fivesamples when folded in quarters; B, slight tear in anyone of five samples whenfolded in half; C, breakage (but two pieces still connected) when folded in half;D, breaks completely into two pieces when folded in half.TEETH-CUTTINGTESTThis test gives a subjective assessment of the resistance experienced by atrained panel of 10 when the test piece is bitten between the upper and lowerincisors. Two slices of 5 mm in thickness and 20 mm diameter were tested.Scores were attributed as follows: 10, extremely strong springiness; 9, verystrong springiness; 8, strong springiness; 7, quite strong springiness; 6, accept-able springiness; 5, acceptable, slight springiness; 4, weak springiness; 3, quiteweak springiness; 2, very weak springiness; 1, mushy texture, no springiness.pH MeasurementA 109 sample was homogenized in 90 ml distilled water and the pH mea-sured using a combination electrode with an Ag/Ag Cl reference system (ModelHI 1911B, Hanna Instruments SpA. Padova, Italy).Microbial AnalysesAEROBIC PLATE COUNTWhole fishballs were ground in a sterile Waring blender flask, using twosamples from each factory. The method as described by APHA (1976) wasused. Plates containing 25-250 colonies were counted after incubation at 35°Cfor 48 h, 20°C for 96 h and 5°C for 144 h.HALOPHILICAND NON-HALOPHILICBACTERIASamples from the plate count were inoculated onto nutrient agar contain-ing 0, 5, 10 and 15% NaCl and incubated at 5°C; 10 and 15% NaCl and incu-bated at 5°C, for 48 and 24 h, respectively. Results were obtained by countingthe number of colonies on the media.91GENERICCHARACTERIZATIONColonies from the plate count and nutrient agar were isolated and identi-fied using the Primary Characterization Tests of Cowan (1975).ResultsPhysical Changes in Fishballs During StorageNo significant changes in the pH and the resilience measured by a FoldingTest were detected after 10 d of storage at 5°C (Table 1). All samples weregraded to M. There were no changes in the teeth-cutting score, after 3 d. How-ever, in terms of appearance and odor, the fishballs became unacceptable onthe fourth day of storage. An unpleasant odor associated with spoilage wasdetected and the surface of the fishballs were covered with slime. The pres-ence of a turbid and viscous exudate was also noticed.Table 1. Physical changes of fishballs during storage at SoC·.Teeth CuttingDay pH Test Appearance/Odor0 7.23 (±0.09) 8(±0.7) Fresh, shiny and glossy, smooth. Fishy.1 7.27 (±0.12) 8(±0.S) Fresh, shiny and glossy, smooth. Fishy.2 7.2S (±0.13) 8(±0.4) Slight exudate, a bit milky, less glossy andshiny. Fishy, slightly pungent odor.3 7.24 (±0.08) 8(±0.S) Slight milky exudate, glossy and wet.Stronger fishy odor.4 7.22 (±0.11) Slimy, milky and viscous exudate, glossyand wet. Slightly unpleasant odor.7 7.18 (±0.10) Slimy. Yellow-milky exudate. Patches ofyellow on fishballs. Unpleasant odor.10 7.30 (±0.08) Slimy. Yellow-milky exudate. Very unpleasantodor.• Average values of samples from six factories.Numbers in brackets are standard deviations of the mean.Effect of Storage on Bacterial FloraThe average number of mesophiles (measured at 35°C) after 1 d storage(Table 2) would be considered unsafe for human consumption if they wereconsumed without re-cooking. By day four the mesophile numbers reached anunacceptable level. The number of psychrotrophs (measured at 5°C), at dayfour, also indicated spoilage of the product.No halophilic psychrotrophs and few halophilic mesophiles were detected(Table 3) indicating that most of the spoilage organisms were of land origin.The non-halophilic psychrotrophs increased with time, while the non-halophilicmesophiles remained virtually constant. Initially, there were twice as manymesophiles as psychrotrophs, but by day three they were approximately equaland thereafter the psychrotrophs predominated.92Table 2. Aerobic plate counts (organisms g-I sample)of fishballs during storage at SOC*.Aerobic plate count (APC)-g-I sampleDay5°C 35°C0 2.2 x 104 (±1.0) 2.6 x 105 (±0.9)1 7.Sx JOS(±2.I) 5.4 x J06 (±1.8)2 2.6 x lOti (±I.7) 6.6 x 106 (±2.0)3 2.2 x 107 (±I.S) 3.6 x 107 (±1.7)4 8.1 x 107 (±2.7) 1.0 x lOB(±I.S)7 1.1 x lOB (±2.3) 2.0 x JOB(±1.8)10 . 1.2 X lOB (±I.S) 2.2 x lOB(±2.2)* Average values of samples from six factories.Numbers in brackets are standard deviations of themean.Table 3. Halophilic and non-halophilic bacteria duringstorage of fishballs at 5°C.Number of coloniesHalophilic Non-halophilicDays of Psychro. Meso Psychro. Mesostorage (5°C) (35°C) (5°C) (35°C)0 - 1 8 141 - - 9 192 - - 11 213 - 1 19 184 - - 21 177 - 1 23 1610 - - 22 15Total % 0 3 113 120(1.3%) (47.9%) (50.8%)* Average values of samples from six factories.Generic CharacterizationTestsResults of the character-ization tests are shown inTable 4. The eight dominantspecies isolated were classi-fied under the terms of ge-nus Aerococcus, Acineto-bacter, Pseudomonas, Sta-phylococcus, Corynebacte-rium, Micrococcus, Strepto-coccus and Enterobacteria.DiscussionFishballs produced inMalaysia have a high initialbacterial contamination andalthough there were nochanges in texture, bacterialspoilage rendered thefishbaIIs unacceptable by thefourth day of storage. Most ofthe fishbaIIs are produced bycottage-scale industries de-pendent upon manual laborand using a minimum ofequipment. The short shelf-life of fishbaIIs may be dueto a combination of some orall of the following points:raw materials that are notfresh and are heavily con-taminated due to poor handling after catch; slow processing at ambient tem-peratures (30-35°C) and poor personal hygiene result in further deterioration ofraw material; use of dirty processing equipment; cooked products are left tocool in rattan baskets on the floor for long periods; packaging is done manually;packed products are often distributed in non-refrigerated vans and lorries;fishbaIIs are sold at ambient temperatures i~' the market.Malaysian law does not permit the use of preservatives in fishbaIIs. Despitethis, many processors have been known to use common preservatives such assodium benzoate to extend the shelf life of their products. This illegal practice isalso harmful to consumers. The shelf-life of fishbaIIs might be improved by re-ducing the initial and subsequent microbial counts through the use of simplerefrigerators and more sanitary working conditions.93Table 4. Generic characterization of bacterial flora isolated from fishballs (based on analyses ofsamples from six factories).Genera ShapeGramstain Motility+Catalase Oxidase Oxidativetest test fermentationW F+ 0+ + 0+ F+ F+ 0F+ FAerococcus CAcinetobacter CPseudomonas RStaphylococcus CCorynebacterium RMicrococcus CStreptococcus CEnterobacteria R+++++ ++C = Cocci; R = Rod; W = Weak reactionin view of the high bacterial contamination and short shelf life of fishballsproduced in Malaysia, a system of quality control must be implemented to im-prove product quality. A study leading to control of all factors related to con-tamination, survival and growth of microorganisms at all stages of fishball pro-cessing, known as the Hazard Analysis Critical Control Point (HACCP) approach,is currently the best system available for improving microbiological safety. Thisstudy will form the basis for future research in fish processing in Malaysia.Although many large factories have been set up to produce surimi-basedproducts in recent years, there is still a niche for small-scale processors of freshfishballs to be sold in the wet markets on the day of production. Consumersshould be advised not to store fishballs for more than 3 d and should cookthem thoroughly before consumption.AcknowledgmentThis project was funded by the Ministry of Science, Technology and theEnvironment, Malaysia, to whom the authors are grateful.ReferencesAPHA. 1976. Compedium of methods for the microbiological examination of foods. AmericanPublic Health Association. Washington, DC.Cowan, S.T. 1975. Manual for the identification of medical bacteria. Cambridge University Press,Cambridge.Hasegawa, H., Editor. 1987. Laboratory manual on analytical methods and procedures for fish andfish products. Marine Fisheries Research Department, Southeast Asian Fisheries DevelopmentCentre, Singapore.Manuscript received 13 December 1993; accepted 17 April 1995.

Effect of storage at 5°C on the bacterial flora and physical properties of Malaysian fishballs

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Effect of storage at 5°C on the bacterial flora and physical properties of Malaysian fishballs

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