Purpose: This study evaluated the effectiveness of HPP holding-temperature (0 to 38℃) on inactivating virus surrogates of MNV-1 and MS2 in pomegranate juice, strawberry juice and puree.
Methods: Murine norovirus (MNV) as a norovirus (NoV) surrogate was inoculated into strawberry or pomegranate juice, and adjusted for initial temperature to reach the process holding-temperature of 10, 20, or 30℃, along with 300 MPa for 3 min for virus inactivation comparison. MS2 coliphage, a relatively HPP-resistant surrogate, was inoculated into strawberry puree and then treated with 600 MPa, 3 min, and holding temperatures of 15 to 38℃.
Results: A regression formula was derived (n=22) for MNV inactivation in juices: Y (log-reduction) = - 0.08 * X (holding-temp.) + 2.6 logs, r2= 0.97. This predicted a 2.6-log reduction of MNV in both juices at HPP 0℃-holding, with MNV inactivation being inversely proportional to temperature increase. When the process temperature and pressure were evaluated individually, the 5-log reduction process for HPP-sensitive MNV in strawberry puree was predicted to be 424 MPa for 3 min at 20℃ holding. On the contrary, surrogate MS2 coliphage inactivation was greater as HPP holding temperature increased (15 to 38℃), all under 600 MPa for 3 min. The increased kill is presumably similar for hepatitis A virus (HAV); but the HPP holding-temperature was not correlated to the reduction level of relatively resistant MS2 in strawberry puree. Overall an increase in process temperature does not resulted in the same killing effect especially for NoV and HAV, although elevated pressure and time generally increase the kill.
Significance: This research provides possible means to manipulate/control HPP process temperature for effective inactivation of different foodborne viruses in fruit juices and puree.