Evaluation Of Chlorine Efficacy Against Escherichia Coli O157:H7 Survival And Cross-Contamination During Continuous Produces Washing Processwith Water Quality Change

Chlorine is widely used by fresh-cut produce processors to reduce pathogens and prevent cross-contamination. However, limited information is available on efficacy of chlorine preventing pathogen survival and the cross-contamination during washing of produce in consideration of wash-water quality change.A study of chlorine against Escherichia coli O157:H7 survival and cross-contamination was conducted simulating produce processors’ washing process. Spinach was inoculated with E. coli O157:H7 and manually washed with uninoculated iceberg lettuce in water with initial free chlorine (FC) of 40mg/L. A total of seven cycles of consecutive washing were conducted until FC ?0.5 mg/L. After every 1 min wash, water and produce were collected to enumerate the surviving E. coli O157:H7 and test water qualities. Water qualities were impacted by consecutive washing and significantly affected the survival and transference of E. coli O157:H7. A reduction of 0.7-0.9 log-CFU/g was observed on spinach. The pathogen survived in wash-water (0.15-13 MPN/ml) and cross-contaminated onto lettuce (11-33 MPN/g), when wash-water’s residual FC was <4.0-mg/L. Results suggested that wash-water quality change severely limits chlorine inactivation of E. coli O157:H7 on produce and in wash-water, which provides useful information for produce processors to develop washwater sanitizing control systems.