Inactivation of a human norovirus surrogate by high-pressure processing: effectiveness, mechanism, and potential application in the fresh produce industry

Fresh produce is often a high-risk food for norovirus contamination because it can become contaminated at both preharvest and postharvest stages and it undergoes minimal or no processing. Currently, there is no effective method to eliminate the viruses from fresh produce. This study systematically investigated the effectiveness of high-pressure processing (HPP) on inactivating murine norovirus (MNV-1), a surrogate for human norovirus, in aqueous medium and fresh produce. We demonstrated that MNV-1 was effectively inactivated by HPP. More than a 5-log-PFU/g reduction was achieved in all tested fresh produce when it was pressurized at 400 MPa for 2 min at 4°C. We found that pressure, pH, temperature, and food matrix affected the virus survival in foods. MNV-1 was more effectively inactivated at 4°C than at 20°C in both medium and fresh produce. MNV-1 was also more sensitive to HPP at neutral pH than at acidic pH. We further demonstrated that disruption of viral capsid structure, but not degradation of viral genomic RNA, is the primary mechanism of virus inactivation by HPP. However, HPP does not degrade viral capsid protein, and the pressurized capsid protein was still antigenic. Overall, HPP had a variable effect on the sensorial quality of fresh produce, depending on the pressure level and type of product. Taken together, HPP effectively inactivated a human norovirus surrogate in fresh produce with a minimal impact on food quality and thus can provide a novel intervention for processing fruits intended for frozen storage and related products such as purees, sauces, and juices.