Levels of Vibrio vulnificus and organoleptic quality of raw shellstock oysters (Crassostrea virginica) maintained at different storage temperatures

Temperature abuse during raw oyster harvesting and storage may allow for the multiplication of natural spoilage flora as well as microbial pathogens, thus posing a potential health threat to susceptible consumers and compromising product quality. The objective of this study was to provide a scientific basis for determining whether different refrigeration and abuse temperatures for raw oysters would result in a spoiled product before it became unsafe. Raw shellstock oysters (Crassostrea virginica) purchased from a commercial Virginia processor were subjected to different temperature abuse conditions (7, 13, and 21 degrees C) over a 10-day storage period. Salinity, pH, halophilic plate count (HPC), total culturable Vibrio counts, and culturable Vibrio vulnificus counts were determined at each abuse condition. V. vulnificus isolates were confirmed by a specific enzyme-linked immunosorbent assay. Olfactory analysis was performed to determine consumer acceptability of the oysters at each abuse stage. The pH of the oysters decreased over time in each storage condition. The HPC increased 2 to 4 logs for all storage conditions, while olfactory acceptance decreased over time. V. vulnificus levels increased over time, reaching 10(5) to 10(6) CFU/g by day 6. The length of storage had a greater effect on the bacterial counts and olfactory acceptance of the oysters (P < 0.05) over time than did the storage temperature (P < 0.05).