Disinfection and Storage Conditions of Fresh Vegetables Prepared for School Lunches on Growth of Bacteria

Abstract

  We objectively evaluated washing and disinfection methods of fresh vegetables at school lunch kitchens. We did this by examining bacteria counts in vegetables washed and disinfected according to School Lunch Practice Standards and bacteria counts in cooked vegetables subjected to secondary contamination.

  Our results can be divided into four main findings. First, washing fresh vegetables with tap water did not affect bacteria counts. Second, continuously running fresh vegetables under slightly acidic electrolyzed water and electrolytic hyposulfite for 3 min had the same bactericidal effect as 5-min immersion in sodium hypochlorite. Third, after storage for 2.5 h at 30℃, there was a negligible increase in bacteria counts in cooked vegetables prepared from vegetables that had been washed and disinfected with electrolyzed water. Fourth, with an increase in storage temperature, bacteria counts tended to increase in cooked vegetables subjected to secondary contamination. However, regardless of storage temperature, the increase in bacteria counts was negligible in the absence of secondary contamination.

  Our results suggest that electrolyzed water could be suitable for disinfecting fresh vegetables in school lunch kitchens. Furthermore, because of its safety and convenience, electrolyzed water is an appropriate alternative to disinfection with sodium hypochlorite. In sum, a suitable disinfection method is washing fresh vegetables with tap water, followed by continuously washing them with electrolyzed water for 3 min, and then washing once again with tap water. In addition, cooked vegetables that have been prepared hygienically can be stored for 2.5 h at 30℃, and it is critical to prevent secondary contamination of fresh and cooked vegetables.