Influence of NaCl on the inactivation of murine norovirus-1 and hepatitis A virus in the Korean traditional salted oyster product “Eoriguljeot” during storage

Abstract

Enteric noroviruses (NoV) and hepatitis A virus (HAV) are the leading causes of non-bacterial shellfish-borne gastroenteritis. This study examined the effects of different concentrations of NaCl on the survival of murine norovirus-1 (MNV-1), which was used as a human NoV surrogate, and HAV in experimentally contaminated raw oysters during 72-h storage at 10°C. Both MNV-1 and HAV titers significantly (p<0.05) decreased by stepwise increases in NaCl and storage time; however, MNV-1 was more resistant to NaCl than HAV. The overall reductions in MNV-1 and HAV titers in oysters incubated with 10%, 7%, 5%, 3%, and 0% NaCl were 0.61 and 1.20, 0.50 and 0.89, 0.35 and 0.64, 0.25 and 0.42, and 0.07 and 0.25 log10 50% tissue culture infectious dose (TCID50)/mL, respectively. A 1.23 log (94.11%) reduction of MNV-1 and 2.45 log (99.65%) reduction of HAV survival also occurred in 10% NaCl-containing oysters at 72h of storage. Using the first-order reaction model, we determined that the MNV-1 decimal reduction time (D-value) was 64h at 10% NaCl, whereas D-values of 63h, 47h, and 31h were obtained for HAV at 5%, 7%, and 10% NaCl, respectively. This study suggests that NaCl concentrations of ≥10% could be potentially used for inactivation of NoV and HAV in traditional Korean foods, including those containing raw oysters such as Eoriguljeot and fermented Jeotgals.