Effect of the Combination of High Hydrostatic Pressure and Alkaline Electrolyzed Water on the Reduction of Heat Resistance of Bacterial Spores.

Abstract

The effect of combined use of alkaline electrolyzed water （AlEW） on the reduction of heat resistance of bacterial spores by high hydrostatic pressure processing（ HPP） was investigated in this study. No reduction of heat resistance of bacterial spores, which was defined as the spore survival by heat treatment at 80℃ for 15 min, was observed by the treatment of single HPP with 30MPa at 50℃ even for 6 hours. However, a 3-log decrease in the viable bacterial spores was obtained by the combination of AlEW pretreatment with 1 hour of HPP treatment. An additional 2 hours duration of HPP treatment could inactivate more 2 logs of the viable bacterial spores. The obtained D value of bacterial spores treated by HPP was decreased to one-eighth by the pretreatment with AlEW when compared with the control sample. In case of the temperature during HPP treatment was 70℃, bacterial spores did not reduce its heat resistance with lower pressuring levels. In case of the temperature during HPP treatment is high with lower pressure levels, bacterial spores did not reduce its heat resistance even when AlEW was combined as the pretreatment. It was considered that the decrease in heat resistance by AlEW was resulted from the weakening of surface layer of spores by protein dissolution with alkaline substance. No clear effect of high negative redox potential, which is a unique property of AlEW, on the reduction of heat resistance was recognized.