Sterilizing effect and mechanism of neutral electrolyzed oxidizing water on cabbage

Abstract: Electrolyzed Oxidizing Water (EOW) as a high efficient fungicide, which has a small amount of chlorine pollution and a little corrosion to metal material in the preparation and use of the process and brings fear and discomfort for people, directly influenced the application in the field of agriculture and food. But Neutral Electrolyzed Oxidizing Water (NEOW) which has a neutral pH value can overcome these shortcomings mentioned above. The sterilizing effect of NEOW, "84"disinfectant, H2O2, and NaClO with the same available chlorine concentration (ACC) were studied in this paper. The influences of the content and existing form of available chlorine, pH value, and sterilization time were systematically studied with in-situ electrochemical-ultraviolet absorption spectroscopy in this paper. The results indicated that the sterilizing effect of NEOW was better than "84"disinfectant, H2O2, and NaClO. While the available chlorine content of NEOW was 24.52 mg/L, the killing rate for Escherichia coli was 95.81%, and the killing logarithm value was 1.38. While the available chlorine content of NEOW was 63.42 mg/L, the killing rate for Escherichia coli was 98.92%, and the killing logarithm value was 1.97. But the killing rate and the killing logarithm value for Escherichia coli of "84"disinfectant (23.38 mg/L), H2O2 (21.66 mg/L), and NaClO(60.33 mg/L) were only 92.22%, 53.29%, 85.42%, and 1.11, 0.33, and 0.84. The sterilizing effect would be enhanced with the ACC increasing in a certain range. When the ACC was 10.72 mg/L, the killing rate and the killing logarithm value for Escherichia coli were 92.86% and 1.15; When the ACC was 63.42 mg/L, the killing rate and the killing logarithm value for Escherichia coli were enhanced to 98.92% and 1.97. But when the ACC was too high, such as 81.92 mg/L, the killing rate and the killing logarithm value for Escherichia coli were slightly reduced to 98.13% and 1.72. The reason lies in the pH value increase of NEOW that would lead to the available chlorine form change when the ACC increased. In the high ACC, the change of pH value had little effect on the sterilization effect. But when the ACC was low, the higher the pH value, the worse the sterilizing effect. When the pH value was 3, 5, and 7 respectively with the ACC 20.55 mg/L, the killing rate and the killing logarithm value for Escherichia coli were 96.28%, 92.68%, and 90.24% and 1.43, 1.14, and 1.01. In addition, the influence of sterilization time on the effect of sterilization was also investigated. The result shows that the increasing of sterilization time is fit to improve the efficiency of sterilization. When killing time was 2 min, 5 min, 8 min, and 10 min with the ACC 20.87 mg/L, the killing rate and the killing logarithm value for Escherichia coli were 69.83%, 77.04%, 89.80%, and 95.68%, and 0.52l L, 0.64, 0.99 and 1.36. The study provides a theoretical basis for the application of neutral electrolyzed oxidizing water. The sterilizing mechanism and optimal sterilization conditions were presented through the study of influence factors of sterilizing effect.