Effects of high hydrostatic pressure on the inactivation of norovirus and quality of cabbage Kimchi

In Korea, cabbage Kimchi is potentially regarded as a high-risk food with respect to enteric norovirus (NoV). This study investigated the effect of high hydrostatic pressure (HPP) treatment (100-500 MPa for 5 min at room temperature) on the inactivation of murine norovirus-1 (MNV-1, initial inoculum of 5-6 log10 PFU/ml) as a human NoV surrogate in the Kimchi. The effects of HHP treatment on the microbiological, physicochemical properties and sensory qualities of cabbage Kimchi were also examined. The MNV-1 in the Kimchi after 100, 200, 300, and 400 MPa were 5.6 (0.1 log reduction), 5.5 (0.2 log reduction), 5.4 (0.3 log reduction), and 4.2 (1.5 log10 PFU/ml), respectively. Complete inactivation of MNV-1 was determined in the cabbage Kimchi by 500 MPa. One-log reduction of total aerobic bacteria and lactic acid bacteria was only determined in the 500 MPa HHP treated Kimchi. The pH values and acidity (%) in all HPP treated Kimchi were 4.4-5.7 and 0.4-0.7%, respectively. The Hunter colors 'a' (redness) and 'b' (yellowness) and mechanical texture (hardness) in HHP Kimchi were not different between 0 MPa and HHP (100-500 MPa) treated Kimchi significantly (P > 0.05) different although the HHP treated Kimchi turned to very slight darkness. All sensory scores in HHP treated Kimchi were determined as > 5 point (like) in 7 point-hedonic scale. The current study suggest that 500 MPa for 5 min could potentially be used for direct application in commercial Kimchi processing and distribution for complete MNV-1 inactivation without causing any deleterious overall quality changes.