Purpose: The purpose of this study was to investigate the effects of different storage temperatures on the microbial prevalence, sensory and textural characteristics of post-harvest shellstock Eastern oysters (Crassostrea virginica).
Methods: Oysters harvested from the Chesapeake Bay, Maryland, during the summer months (June, July, and August, 2010) were subjected to different storage temperatures (5, 10, and 20°C) over a period of 10 days. At selected time intervals (0, 1, 3, 7, 10 days) two separate samples of 6 oysters each were homogenated and analyzed for pH, halophilic plate counts (HPC), total Vibrio, and Vibrio parahaemolyticus. Sensory evaluation was performed for acceptability, appearance and odor of oyster meats shucked after storage at the test temperatures and times. Texture analysis was performed using a texture analyzer on meats shucked from oysters held under the same conditions as for sensory.
Results: The pH of the oyster homogenate showed no consistent pattern with storage time and temperature. The HPC (4.5 to 9.4 log CFU/g) were highest on day 10 while olfactory acceptance reduced with time and increasing storage temperatures. The V. parahaemolyticus counts increased over time from 3.5 to7.5 MPN/g by day 10. Loss of freshness as judged by appearance and odor was significant over time (P < 0.05). Toughness of oysters increased with storage time at 5 and 10°C from day 1 to day 3, but was inconsistent after day 7.
Significance: The results indicate that the length of storage and temperature had a significant effect on bacterial counts and olfactory acceptance of oysters but had an inconsistent effect on texture.