Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2002
Publication Date: 10/1/2002
Interpretive Summary: The process of "pressure pasteurization" is a new commercial process applied to raw shellfish for the purposes of pathogenic bacterial inactivation. In this publication, we explored the possibility of inactivating nonenveloped viruses, principally hepatitis A virus and Norwalk virus, for which raw shellfish consumption is a common source of outbreaks. We demonstrated that approximately 4500 atmospheres (atm) of pressure for 5 min completely inactivated high titer HAV stock with lesser degrees of inactivation observed between 4500 and 3000 atm. Enhanced inactivation of HAV was observed when treatments were extended to 15 minutes. However, when HAV was diluted in seawater, reduced sensitivity to pressure was observed. Since Norwalk virus cannot be propagated in vitro and pressure treatment does not destroy the viral RNA, neither live plaque assays or RT-PCR methods could be useful to evaluate Norwalk inactivation. Therefore, a genetically-related virus, feline calicivirus, (FCV) as evaluated and shown to be inactivated at 3000 atm. Poliovirus, a virus which is genetically related to HAV, was not inactivated at pressures as high as 6000 atm. This work shows that "pressure pasteurization" can be a viable process for HAV-contaminated shellfish. Whether similar pressures will be sufficient to inactivate Norwalk virus remains to be determined.
Technical Abstract: Potential application of high hydrostatic pressure processing (HPP) as a method for viral sterilization was evaluated. A 7-log10 PFU/ml hepatitis A virus (HAV) stock, in tissue culture medium, was reduced to zero PFU after exposure to >450 megapascals (MPa) for 5 min. Titers of HAV were reduced in a time- and pressure-dependent manner between 300 and 450 MPa. In contrast, poliovirus titer was unaffected by a five-min treatment at 600 MPa. Dilution of HAV in seawater increased the pressure resistance of HAV, suggesting a protective effect of salts on virus inactivation. A series of RNase protection experiments indicated that viral capsids may remain intact during pressure treatment, suggesting that inactivation was due to subtle alterations of viral capsid proteins. A 7-log10 PFU/ml stock of feline calicivirus, a Norwalk virus surrogate, was completely inactivated after 5 min treatments with >275 MPa. These data show that HAV and a Norwalk virus surrogate can be inactivated by HPP and suggest HPP will be capable of rendering potentially contaminated raw shellfish free of infectious virus.