Abstract
The disinfection efficacy of sodium hypochlorite (NaClO) and chlorine dioxide (ClO2) was evaluated singly or in combination with micro-bubbling, ultra-sonication, or mild heat (50°C) against microorganisms on lettuce, spinach and Chinese cabbage. There were no significant differences in reductions of either intrinsic microflora or inoculated Escherichia coli O157:H7 between 5 and 10 min of treatment time, between 50, 100, 200 ppm NaClO, or between 25 and 50 ppm ClO2. However, mild heat (50°C) significantly enhanced efficacy, with maximum log reductions of 2.91 in total plate count, 4.10 in total coliform count, and 2.13 – 2.53 in E. coli O157:H7. Heat was more effective when applied before or with chlorination than after. The concentration and efficacy of the chlorine wash water gradually decreased with reuse, allowing cross-contamination when the initial concentration was less than 50 ppm. These results can be used to guide the fresh-cut vegetable industry in designing chlorine-based treatments for better control of safety and quality.
