Synergistic Effects of Combined Chlorine and Vitamin B1 on the Reduction of Murine Norovirus-1 on the Oyster (Crassostrea gigas) Surface.

This study investigated the synergistic effects of combined chlorine (200, 500, 700, and 1000 ppm) and vitamin B1 (1000, 2000, and 3000 ppm) on the murine norovirus-1 (MNV-1), a human norovirus (NoV) surrogate, on oyster surface. Vitamin B1 slightly reduced MNV-1 (0.04-0.3 log-reduction), whereas chlorine significantly reduced MNV-1 (0.4-1.0 log-reduction). The combined chlorine and vitamin B1 resulted in a 0.52-1.97 log-reduction of MNV-1. The synergistic reduction in the MNV titer was not dependent on the concentrations of chlorine and vitamin B1, and it ranged between 0.08 and 1.03 log10 PFU/mL. The largest synergistic reduction observed was for the combined 700 ppm chlorine and 1000 ppm vitamin B1. The pH and mechanical texture of the oysters were not significantly changed by the combined 0-1000 ppm chlorine and 3000 ppm vitamin B1. The overall sensory acceptability were significantly (P < 0.05) reduced in oysters treated with 1000 ppm chlorine and 3000 ppm vitamin B1 than in those treated with 0-700 ppm chlorine and 3000 ppm vitamin B1. This study suggests that the combined 700 ppm chlorine and 3000 ppm vitamin B1 could potentially be used to reduce NoV on oyster surface without causing concomitant changes in the mechanical texture, pH, or sensory qualities of the oysters.