Decontamination of lettuce using acidic electrolyzed water

The disinfectant effect of acidic electrolyzed water (AcEW), ozonated water , and sodium hypochlorite (NaOCl) solution on lettuce was examined. AcEW (p H 2.6; oxidation reduction potential, 1140 mV; 30 ppm of available chlorine ) and NaOCl solution (150 ppm of available chlorine) reduced viable aerobes in lettuce by 2 log CFU/g within 10 min. For lettuce washed in alkaline el ectrolyzed water (AlEW) for 1 min and then disinfected in AcEW for 1 min, v iable aerobes were reduced by 2 log CFU/g. On the other hand, ozonated wate r containing 5 ppm of ozone reduced viable aerobes in lettuce 1.5 log CFU/g within 10 min. It was discovered that AcEW showed a higher disinfectant ef fect than did ozonated water significantly at P < 0.05. It was confirmed by swabbing test that AcEW, ozonated water, and NaOCl solution removed aerobi c bacteria, coliform bacteria, molds, and yeasts on the surface of lettuce. Therefore, residual microorganisms after the decontamination of lettuce we re either in the inside of the cellular tissue, such as the stomata, or mak ing biofilm on the surface of lettuce. Biofilms were observed by a scanning electron microscope on the surface of the lettuce treated with AcEW. Moreo ver, it was shown that the spores of bacteria on the surface were not remov ed by any treatment in this study. However, it was also observed that the s urface structure of lettuce was nor damaged by any treatment in this study. Thus, the use of AcEW for decontamination of fresh lettuce was suggested t o be an effective means of controlling microorganisms.