Comparison of the murine norovirus-1 inactivation in cabbage Kimchi with two different salinities during storage

• MNV-1 reduction in normal-salinity Kimchi was 1.75 log PFU/ml at 5 °C for 10 weeks.
• MNV-1 reduction in low-salinity Kimchi was 1.24 log PFU/ml at 5 °C for 10 weeks.
• > 90% reduction of MNV-1 in normal-salinity Kimchi was faster than low-salinity Kimchi.

Enteric noroviruses are occasionally detected in Kimchi, which is a traditional dish made of fermented vegetables. This study was aimed at examining the effects of two levels of salt concentrations on the survival of murine norovirus-1 (MNV-1), a human norovirus surrogate, in experimentally contaminated cabbage Kimchi stored at 5 °C for 10 weeks. The number of total aerobic bacteria (TAB) and lactic acid bacteria (LAB), MNV-1 titer pH, and acidity were measured every week. The titers of MNV-1 in both low (1.17%) and normal (2.22%) salinity cabbage Kimchi were significantly (P < 0.05) decreased with increase in storage time. The overall reduction was 1.75 log10 plaque-forming unit (PFU)/mL in normal salinity cabbage Kimchi and 1.24 log10 PFU/mL in low salinity cabbage Kimchi. The time required to reduce the titer by > 1 log10 PFU/mL in normal and low salinity cabbage Kimchi were 4 and 8 weeks, respectively. The pH value under both salinities significantly (P < 0.05) decreased until 4 weeks. The maximum acidity was 0.83% and 0.79% in normal and low salinity cabbage Kimchi, respectively, during the 10 weeks. The population of TAB and LAB reached up to 7.33 log10 colony-forming unit (CFU)/g as a maximum population during the storage period of 3 weeks in normal salinity cabbage Kimchi. However, the population of TAB and LAB in low salinity cabbage Kimchi reached to 6.99 and 7.04 log10 CFU/g at 5 and 4 weeks, respectively. Through these findings, fermentation factors such as TAB, LAB, pH, and acidity of cabbage Kimchi were influenced by salt concentration. The inactivation of MNV-1 in normal salinity cabbage Kimchi was much faster than that in low salinity cabbage Kimchi because the fermentation in normal salinity cabbage Kimchi progressed more quickly than that in low salinity cabbage Kimchi. However, both salinity cabbage Kimchi were able to infect cells for 70 days even though the MNV-1 was reduced over 1 log10 during fermentation. Therefore, the way to protect cabbage Kimchi from norovirus must be considered.

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