Efficacy of Low-temperature High Hydrostatic Pressure Processing in Inactivating Vibrio parahaemolyticus in Pure Culture and Oyster Homogenates

Sureerat Phuvasate* and Yi-Cheng Su
2014 IFT Annual Meeting & Food Expo

Vibrio parahaemolyticus (Vp) is the leading cause of gastroenteritis associated with consumption of raw and undercooked seafood, particularly oysters. High hydrostatic pressure processing (HPP) can be utilized as a post-harvest process to eliminate Vp in raw oysters. This study investigated the susceptibility of five environmental isolates and five clinical strains of Vp in 2% NaCl solution to HPP (200 or 250 MPa for 5 min) at low temperatures (5 and 15°C). Survival of Vp was determined by spread-plate method using trypticase soy agar containing 2% NaCl. Among the strains tested, Vp 10290 (clinical strain) and Vp 100311Y11 (environmental strain) were two most pressure-resistant strains while Vp 10292 (clinical strain) was the least resistant strain. These three strains were further studied for resistance to pressures in sterilized oyster homogenates. A treatment of 200 MPa at 15 °C reduced counts of strains 10290, 100311Y11 and 10292 in oyster homogenates by 0.8, 1.1 and 3.4 log CFU/g, respectively. Reductions of these strains increased significantly (P < 0.05) to 1.6, 2.4 and 4.6 log CFU/g, respectively, in oyster homogenates treated with 200 MPa at 5°C. A HPP treatment of 250 MPa at 5°C also significantly (P < 0.05) increased reductions of strains 10292, 10290 and 100311Y11 in oyster homogenates to >7.3, 6.2 and 6.2 log CFU/g, respectively, from 6.1, 4.2 and 4.3 log CFU/g, respectively, yielded from a treatment of 250 MPa at 15°C. Efficacy of HPP in inactivating Vp in oysters can be enhanced by lowering operation temperature to 5°C. Pressure resistance among strains and processing parameters such as pressure and temperature are factors to be considered for improving the safety of pressure-treated oysters.