44-4 |
Influence of agar type on determination of microbiological quality of bivalves |
M. A. KHAN, Biochemistry, Meomorial University of Newfoundland, St. John's, NF A1B 3X9, Canada, F. SHAHIDI, Biochemistry, Memorial University of Newfoundland, St. John's, NF A1B 3X9, Canada, and C. Parrish, Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, NF A1C 5S7, Canada. Plate count agar (PCA) has been used to evaluate microbial quality in seafoods, although it lacks the salt and minerals necessary for marine bacteria. Marine agar (MA) contain the necessary elements required for growth of marine bacteria. Nonetheless, MA has not been used to evaluate the microbial quality of bivalves. Total heterotrophic bacterial counts (THBC) in bivalves indicate to the general microbial quality of the seafood, while psychrotrophic bacteria (PB) are the main contributor to the spoilage of seafoods under refrigeration. The objective of this study was to compare the determination of THBC and PB counts using PCA and MA in wild and cultured blue mussels and scallops stored at 2C. Cultured blue mussels (CM), wild blue mussels (WM), cultured scallops (CS) and wild scallops (WS) were used in this study. Samples (5-6 animals) were stored at 2C and analyzed on days 0, 3 and 7. Samples were homogenized, serially diluted, spread on pre-poured PCA and MA plates and incubated at 4 C for 10 days to determine PB and at 30 C for 48 h to determine THBC. Colonies were counted and recorded as log colony forming unit (log CFU/g) of the mussel meat. Our results showed that, CM at 0 day had THBC of log 4.32±0.08 on MA but only log 3.36±0.06 on PCA. After 7 days, the THBC of CM reached log 8.47±0.05 while the counts on PCA were only log 6.57±0.03. Psychrotrophic bacteria counts of CMA after 7 days were log 6.87±0.01 on MA but only log 5.69±0.11 on PCA. Similar trends were observed using WM, CS and WS samples. These results suggest that agar type influences the determination of microbial quality of bivalves. Therefore, it is possible to suggested that the use of PCA to evaluate the microbial quality of bivalves be replaced with MA.
Session 44, Seafood Technology: Safety
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