Effect of Ethanol Concentration on Escherichia coli Sterilization using Pulsed Electric Field Application

This study examined the killing effects of ethanol solution using a pulsed electric field (PEF). We applied PEF (field intensity: 5.5 kV/mm, pulse length: 4 $\mu$s, number of applied PEF: 10-1,000, frequency: 10 Hz) to a liquid sample that is 0%–40% ethanol solution, which contains Escherichia coli. The results are as follows; (i) The survival counts of E. coli decreased with an increase in the number of applied pulses. (ii) The survival counts of E. coli decreased as ethanol concentrations and sample temperatures increased; PEF kills E. coli in 30%–40% ethanol solution after pulse application. (iii) The survival counts of E. coli decreased with an increase in the sample temperature. For the 20% ethanol sample at high temperature, we cannot observe the colonies of E. coli after PEF experiments. (iv) The energy consumption for the PEF sterilization (100 pulses application) in a room temperature sample is less than that for sake pasteurization.