Survivability of Inoculated Versus Naturally Grown Bacteria in Liquid Foods under Pulsed Electric Fields

Abstract

In this paper, the effect of different pulse and system parameters on the killing efficiency of PEF treatment was investigated. Escherichia Coli bacteria inoculated in apple juice was treated. The results showed that an electric field higher than 4 kV/mm is required to enhance the killing efficiency using PEF that has sufficient log reductions in the microbial numbers. The temperature rise during pulse application was found to be around 20degC, and it is observed that this rise in medium temperature has synergistic effect and has resulted in high inactivation. As the temperature rise can be limited to a value below the pasteurization temperature, the synergistic effect can be highly beneficial. While high killing rate was achieved for inoculated bacteria (3-4 log reduction), less than 2 log reduction was achieved for naturally growing bacteria in apple juice under the test conditions used.