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.