Abstract
Acidic hypochlorite (prepared by addition of NaOCl and HCl to water) and electrolyzed acidic water (prepared by electrolysis of 0.1% NaCl, recognized as a food additive) were compared with regard to their disinfectant activities against food-borne pathogens and their mechanisms of disinfectant activities were examined. The both disinfectants reduced colony forming units of vegetative cells by more than 6 log units in 10 seconds. Spores of Clostridium botulinum and Bacillus subtilis were reduced by 5.0 and 1.8 log units, respectively, in 10 minute treatments by these disinfectants. The extents of reductions were significantly more than that by sodium hypochlorite at a same free chlorine concentration. Normal flora in bean sprout was reduced by either of the acidic hypochlorite and electrolyzed acidic water more effectively than sodium hypochlorite. Electron microscopic observations revealed that numerous structures that appeared like membrane vesicles formed on the surface of gram negative rods exposed to the two disinfectants. The exposed bacteria did not show the plasmolysis when subjected to hypotonic treatment. Propidium iodide which does not penetrate through the intact cytoplasmic membrane invaded into the cytoplasm of the disinfectant exposed bacterial cells. These observations suggested that the disinfectants killed bacteria by destruction of their cell wall and cytoplasmic membrane. No difference was found between the two disinfectants, indicating that acidic hypochlorite, which is prepared quite inexpensively by just an addition of HC1 to sodium hypochlorite solution, is as effective, and has the same mechanism of action, as electrolyzed acidic water.
