Hurdle enhancement of slightly acidic electrolyzed water antimicrobial efficacy on Chinese cabbage, lettuce, sesame leaf and spinach using ultrasonication and water wash

Slightly acidic electrolyzed water (SAEW) is well known as a good sanitizer against foodborne pathogens on fresh vegetables. However, microbial reductions from SAEW treatment are not enough to ensure produce safety. Therefore, it is necessary to improve its antimicrobial efficiency by combining it with other appropriate approaches. This study examined the microbicidal activity of SAEW (pH 5.2-5.5, oxidation reduction potential 500-600 mV, available chlorine concentration 21-22 mg/l) on Chinese cabbage, lettuce, sesame leaf and spinach, four common fresh vegetables in Korea under same laboratory conditions. Subsequently, effects of ultrasonication and water wash to enhance the sanitizing efficacy of SAEW were studied, separately. Finally, an optimized simple and easy approach consisting of simultaneous SAEW treatment with ultrasonication (3 min) followed by water wash (150 rpm, 1 min) was developed (SAEW + US-WW). This newly developed hurdle treatment significantly enhanced the microbial reductions compared to SAEW treatment alone, SAEW treatment with ultrasonication (SAEW + US) and SAEW treatment followed by water wash (SAEW-WW) at room temperature (23 ± 2 °C). Microbial reductions of yeasts and molds, total bacteria count and inoculated Escherichia coli O157:H7 and Listeria monocytogenes were in the range of 1.76-2.8 log cfu/g on different samples using the new hurdle approach.