Effects of sodium hypochlorite on the potential infectivity of human norovirus GII.4 using propidium monoazide with RT-qPCR and quality assessments in Manila clams (Ruditapes philippinarum)

This study investigated the effect of NaOCl on the inactivation of human norovirus (HNoV) GII.4 infectivity in Manila clams treated with NaOCl solution at 100-1000 mg/L chlorine for 10 min using propidium monoazide (PMA)/RT-qPCR. HNoV GII.4 detected using non-PMA/PMA were significantly (p < .05) reduced to 0.15/0.37, 0.33/0.58, 0.59/0.85, 0.69/0.99, and 1.05/1.54 log(10)copy number/mu l upon a 10 min treatment with 100, 300, 500, 700, and 1000 mg/L of NaOCl, respectively. The D-value of HNoV GII.4 infectivity in non-PMA and PMA-treated samples was calculated as 1000 and 714.3 mg/L of NaOCl, respectively, using the first-order kinetics model. The pH value increased significantly as chlorine concentration increased. Changes in color and appearance in quantitative analysis evaluation did not appear after treatment with 100-1000 mg/L chlorine although all sensorial parameters were above 4 points in all NaOCl treatments. The highest score of overall acceptability was observed in 100-500 mg/L chlorine-treated Manila clams. Practical applications The results suggest that PMA/RT-qPCR could help distinguish HNoV infectivity by negatively affecting clam flavor following NaOCl treatment with 1000 mg/L of chlorine. Moreover, the inactivation kinetics of chlorine against HNoV might provide further information for Manila clam processing and distribution.