Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2009
Publication Date: 2/20/2009
Citation: Kingsley, D.H., Chen, H. 2009. Influence of pH, Salt and Temperature on Pressure Inactivation of Hepatitis A virus. Food Microbiology. 130:61-64.
Interpretive Summary: High pressure processing (HPP) is a technology that can inactivate pathogens within foods without cooking. This technology is particularly appealing to the shellfish industry because it can also facilitate shucking of oysters and clams. A number of food-borne viruses can be inactivated by high pressure processing (HPP), including hepatitis A virus (HAV) and norovirus surrogates. Previously, we have found that temperature and the composition of the food environment can influence HPP inactivation of viruses. Unlike other viruses tested to date, HAV inactivation is enhanced when pressure is applied at warmer temperatures, while other viruses are more readily inactivated at refrigeration temperatures. In this publication, we investigate the potential for enhanced inactivation of HAV within an oyster matrix at warmer temperatures and characterize HAV’s inactivation at different salt concentrations and at acidic pHs. Overall, we find that there would be no additional benefit to performing HPP at elevated temperatures for shellfish potentially contaminated with HAV. However, we do observe enhanced HPP sensitivity for HAV at lower pHs, thus HPP is well suited for inactivation of HAV in acidic foods such as salsa and fruit juices.
Technical Abstract: 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 50C. Decreasing solution pH enhanced pressure inactivation of HAV. This enhanced inactivation effect was most evident at 20C. A baroprotective effect was observed for NaCl concentrations from 1 to 6%. For example, a treatment of 400 MegaPascals (MPa) for 1 min at 50C 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 solution. The pressure resistance of HAV in oysters was also examined. Temperature in a range of 5 and 50C 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 useful information for designing product formulations and processing parameters for high pressure processing, such as low pH fruit juices and salsa.