Why Food-Poisoning Bacteria Attached to Shredded Cabbage Are Not Efficiently Disinfected by Sodium Hypochlorite (NaCIO)

摘要

The aim of this study was to determine why food poisoning bacteria attached to cut cabbage are not efficiently disinfected by sodium hypochlorite (NaCIO). Pretreatment of shredded cabbage with diethyl ether definitely decreased the survival numbers of Escherichia coli 0157:H7 and Salmonella spp. after disinfection with 100 ppm of NaCIO. The density of E. coli 0157:H7 at the cut edge of a cabbage section was larger than that on the surface. The residual ratio of attached bacteria at the cut edge after NaCIO disinfection was significantly higher than that on the surface. Microscopical observation indicated that the cut edge of shredded cabbage pretreated with diethyl ether was almost closed, resulting in a decrease in bacterial infiltration. Pretreatment of shredded cabbage with a higher concentration of NaCIO to penetrate it more deeply significantly decreased the numbers of surviving bacteria after NaCIO disinfection. Based on these results, we concluded that the bacteria attached to cut cabbage were not efficiently disinfected by NaCIO, because not enough NaCIO deeply infiltrated into the cut edges, and hence not enough came in contact with the bacteria.