Application of gamma irradiation for the reduction of norovirus in traditional Korean half-dried seafood products during storage

Gwamegi (half-dried Pacific herring or Pacific saury) and semi-dried squid are not subject to any heat treatment during processing, and can become contaminated with norovirus (NoV). This study investigated the effects of gamma irradiation (0, 3, 5, 7, and 10 kGy) on the inactivation of murine norovirus-1 (MNV-1) and the survival of MNV-1 in Gwamegi and semi-dried squid samples following their irradiation and storage at 10 °C for 7 days. The overall reductions of MNV-1 in Gwamegi were 0.66, 0.88, 1.31, and 1.66 log10 PFU/ml by 3, 5, 7, and 10 kGy irradiation, respectively. The overall reductions of MNV-1 in semi-dried squid were 0.59, 0.88, 1.36, and 1.81 log10 PFU/ml by 3, 5, 7, and 10 kGy irradiation, respectively. There was an approximate 1 log10 reduction in viral load for all irradiated samples stored at 10 °C for 7 days at doses of 3, 5, 7, and 10 kGy including non-irradiated samples. Our findings suggest that gamma irradiation using a dose ≥7 kGy could be effective in reducing MNV-1 titers by more than 1 log10 PFU/mL (>90%) in half-dried seafood products, without any concomitant changes in color and sensory evaluation.