Influence of pH, salt, and temperature on pressure inactivation of hepatitis A virus.

The effects of pH (3-7), NaCl (0-6%), and temperature on pressure inactivation of hepatitis A virus (HAV) were determined. The HAV samples were treated at 400 MPa for 1 min at 5, 20, and 50 degrees C. Decreasing solution pH enhanced pressure inactivation of HAV. This enhanced inactivation effect was most evident at 20 degrees C. A baroprotective effect was observed for NaCl concentrations from 1 to 6%. For example, a treatment of 400 MegaPascals (MPa) for 1 min at 50 degrees C reduced the HAV titers by 4.0, 4.1, 1.3 and 0.4 log plaque forming units (PFU)/ml for NaCl concentrations of 0, 1, 3, and 6%, respectively. Overall, increasing the treatment temperature enhanced pressure inactivation of HAV in the solutions. The pressure resistance of HAV in oysters was also examined. Temperature in the range of 5 to 50 degrees C did not significantly affect the pressure inactivation of HAV within oyster homogenates. It is concluded that HPP treatment of oysters at temperatures above room temperature would not provide any additional benefit for inactivation of HAV. However, the observation that HAV inactivation is enhanced in acidic matrices is information that may be useful for designing product formulations and processing parameters for high pressure processing of products such as low pH fruit juices and salsa.