Conditions for high pressure inactivation of Vibrio parahaemolyticus in oysters

The objective of this study was to identify the high pressure processing conditions (pressure level, time, and temperature) needed to achieve a 5-log reduction of Vibrio parahaemolyticus in live oysters (Crassostrea virginica). Ten strains of V. parahaemolyticus were separately tested for their resistances to high pressure. The two most pressure-resistant strains were then used as a cocktail to represent baro-tolerant environmental strains. To evaluate the effect of temperature on pressure inactivation of V. parahaemolyticus, Vibrio-free oyster meats were inoculated with the cocktail of V. parahaemolyticus and incubated at room temperature (approximately 21 degrees C) for 24 h. Oyster meats were then blended and treated at 250 MPa for 5 min, 300 MPa for 2 min, and 350 MPa for 1 min. Pressure treatments were carried out at -2, 1, 5, 10, 20, 30, 40, and 45 degrees C. Temperatures >/=30 degrees C enhanced pressure inactivation of V. parahaemolyticus. To achieve a 5-log reduction of V. parahaemolyticus in live oysters, pressure treatment needed to be >/=350 MPa for 2 min at temperatures between 1 and 35 degrees C and >/=300 MPa for 2 min at 40 degrees C.