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Influence of water antimicrobials and storage conditions on inactivating MS2 bacteriophage on strawberries

Huang, Licheng, Luo, Xin, Gao, Jingwen, Matthews, Karl R.
International journal of food microbiology 2019 v.291 pp. 67-71
Norovirus, anti-infective agents, bacteriophages, chlorine, electrolyzed water, food safety, fresh produce, frozen storage, storage temperature, strawberries, tap water, washing
Foodborne illnesses caused by norovirus contaminated fresh produce remain a food safety concern worldwide. In the present study, the impacts of commercial and home processing conditions of strawberries were evaluated for inactivation of the MS2 bacteriophage. MS2 was used as a surrogate of norovirus and was spot inoculated onto strawberries to achieve 6.6 log PFU/g. The inoculated strawberries were washed with tap water, electrolyzed water, or 50 ppm chlorine for 90 s prior to and after storage. After initial washing, the strawberries were separately stored at −20 °C and −80 °C for 30 days. Change in MS2 populations on strawberries was evaluated by plaque assay method on day 1, 15, and 30 for −20 °C and −80 °C groups. The results showed that washing strawberries prior to storage resulted in a significant decrease (approximately 1 log PFU/g) of MS2 population regardless of the treatment (p < 0.05). Frozen storage had minor effects on inactivating MS2, which resulted in approximately a 0.5 log PFU/g reduction at the end of storage. Washing frozen berries in electrolyzed water or 50 ppm chlorine on day 30 resulted in an additional 1 log PFU/g decrease in MS2 compared to water alone. These results suggest that washing strawberries with a chemical antimicrobial prior to and post frozen storage may enhance microbial safety.