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Investigation of non-heating sterilization method of packed fresh foods by pulsed electric field

Currently, foods have been mainly sterilized using chemicals, heating and ultraviolet rays. However, these methods have some problems, for example, the change of the taste and constituent of fresh foods, the risk of the residual chemicals and low efficiency. To solve these problems, the sterilization by the pulsed electric field has been proposed. When the pulsed electric field is applied to a bacterium or fungus, the voltage concentrates to the membrane of it. If the membrane has over 1V of the voltage, breakdown occurs in the membrane. As a result, a pore is made on the membrane and it is sterilized. However, in the case of packed food, since a packing plastic bag is an insulator, the electric field didn't be applied to the bacteria and fungi. In the sterilization by the pulsed electric field, a cell can be written as equivalent circuits by capacitors and resistors. The membrane is the capacitor and the cytoplasm is the resistor. Also the foods can be written as equivalent circuits by capacitors and resistors and a packing plastic bag is written as the capacitor. Therefore, the intensities of the electric field applying to the cell and the bag are changed by the frequency of applying pulsed electric field. This work focuses on sterilization of the packed fresh foods by the pulsed electric field. In this study, we have investigated the sterilization ratios of E. coli packed by a plastic film for the voltage pulses of several frequencies.