Evaluating wet and dry contact time of contaminated produce with chlorine solution against Listeria monocytogenes and Salmonella enterica

Chlorine is the most widely used sanitizer, however, there are varying reports on the exposure time and its effectiveness on fresh produce. This study determined the minimum exposure time for wet and dry contact chlorine treatments with the highest efficacy in reducing Listeria monocytogenes and Salmonella enterica on spinach and bell pepper surfaces. The chlorine wash at 100 mg/L for 1 min resulted in a significant reduction (p < 0.05) of both pathogens on both produce. S. enterica was reduced by 4.86 log CFU/g on spinach and by 3.97 log CFU/g on bell pepper, while L. monocytogenes was reduced by 3.7 log CFU/g on spinach and by 3.08 log CFU/g on bell pepper. The majority of Listeria cross-contamination (>2.30 log CFU/g) on un-inoculated spinach and bell peppers was observed within 1 min of chlorine washing. Cross-contamination of Salmonella on spinach was >2.9 log CFU/g within 1 min and the level increased to 4.21 log CFU/g after 6 min. This study showed that washing spinach and bell pepper for up to 6 min with a 100 mg/L chlorine solution did not achieve additional reductions in L. monocytogenes and S. enterica populations compared to a 1 min wash.