Antiviral capacity of sanitizers against infectious viruses in process water from the produce industry under batch and continuous conditions

The presence of human enteric viruses in produce has extensively been reported. However, the significance of the quality of process water (PW) used by the produce industry and the viral inactivation capacity of water disinfection agents used to maintain the microbiological quality of PW has received limited attention. This study evaluates the antiviral disinfection efficacy of chlorine, chlorine dioxide (ClO2) and peracetic acid (PAA) at recommended operational limits in PW using hepatitis A virus (HAV), the cultivable norovirus surrogate, murine norovirus (MNV-1), and MS2 coliphages. Defined commodity representative crops (baby leaves, bell peppers, and the vegetable mix of tomatoes, cucumbers, peppers, and onions) associated with specific water-based processes were studied. Two systems classified as either batch or continuous system were used. The continuous system allows the continuously entrance of sanitizer solution and organic matter added to the washing tank to simulate the conditions of an industry wash tank. Batch scale experiments showed that 20 mg/L chlorine and 3 mg/L chlorine dioxide completely inactivated MNV-1 and MS2 (mean of 5 log) after 1 min contact time regardless of the PW type. However, the infectivity of HAV was reduced only by less than 2 log after 1 min for chlorine and chlorine dioxide and the complete inactivation was not observed even after 10 min. On the contrary, residual viral infectivity/viability of HAV, MNV-1 and MS2 was observed for PAA in the three types of PW. The inactivation kinetic models for MS2 coliphages were developed based on the data obtained under the continuous system comparing the three types of PW. Chlorine (5 mg/L) and chlorine dioxide (2-3 mg/L) avoided the accumulation of MS2 below the detection limit while PAA (80 mg/L) was unable to prevent it independently of the type of PW. In summary, in the washing operation, it is a key objective to reach virus inactivation through the selection of the most effective sanitizer by guaranteeing that sufficient concentration and contact times prevent the risk of viral cross-contamination.