Bactericidal effect of four types of electrolyzed water on fresh-cut vegetables

Electrolyzed water containing 10-80 ppm available chlorine is being used in some commercial plants as an alternative disinfectant to sodium hypochlorite. In 2012, electrolyzed weakly acidic water (EWeAW) (pH 2.7-5.0) was approved as a food additive by the Ministry of Health, Labor, and Welfare of Japan in addition to electrolyzed strongly acidic water (EStAW) (pH KLEINERDAN2.7), electrolyzed slightly acidic water (ESlAW) (pH 5.0-6.5), and electrolyzed slightly alkaline water (ESAlW) (pH GROTERDAN7.5) that had previously been approved. In this study, effects of the four types of electrolyzed water containing 30-50 ppm available chlorine on fresh-cut lettuce, cabbage, cucumber, and Welsh onion were determined based on bacterial enumeration and identification. The fresh-cut vegetables had 5.1-8.0 log CFU g-1 for mesophiles and 3.4-7.0 log CFU g-1 for coliforms, with the counts being the highest in Welsh onion followed by cucumber and then lettuce or cabbage. The bacterial flora of fresh-cut vegetables was comprised of soilborne organisms such as Bacillus and Curtobacterium and phytopathogenic organisms such as Pantoea and Psedomonas, except that Welsh onion predominantly contained Enterobacteriaceae such as Rahnella and Serratia. Rinsing treatments reduced the counts of mesophiles or coliforms on all fresh-cuts by 0.4-1.5 logs relative to non-treated samples regardless of the type of electrolyzed water. When bacteria were isolated from each fresh-cut vegetable after treatment with the most effective type of electrolyzed water based on the reduction of bacterial counts, the ESlAW and EWeAW reduced the number of bacterial genera or species detected in fresh-cut lettuce and cucumber, respectively, while the EStAW and ESAlW did not reduce the diversity of bacterial flora of fresh-cut cabbage and welsh onion, respectively. These results indicate that any electrolyzed water reduced the bacterial counts on fresh-cut vegetables, but the effectiveness on bacterial flora differed with type of water and vegetable.