Investigation of selective sterilization of unnecessary microorganisms on pulsed electric field sterilization

Abstract

This study focuses on the selective sterilization of fermented foods by Intense Pulsed Electric Field (IPEF). Since IPEF can make pores penetrating a membrane of a cell, the principle of the sterilization by IPEF is irreversible electroporation that releases the contents through the pores of the cell membrane of microorganisms. Beneficial microorganisms are added in an ingredient on the manufacturing process of the fermented foods. On the process, other unnecessary microorganisms threaten to contaminate the food. In that case, it is necessary that only unnecessary microorganisms are sterilized. Heat is used to sterilize foods. However, heat sterilization also sterilizes the beneficial microorganisms and loses the flavor of the fermented foods. In this study, we used lactic acid bacterium and yeast for the beneficial microorganism and unnecessary microorganism, respectively. The conditions which can kill lactic acid bacteria and yeasts have been investigated. Lactic acid bacteria cannot be killed at 500 pulses of the pulse electric field with 10 kV/cm and 50 pulses of the pulse electric field with 20 kV/cm. On the other hand, yeasts have been able to be killed at same conditions. The killing rate of yeasts is about 2 times high compared to that of lactic acid bacteria by applying 500 pulses of IPEF with 10 kV/cm of electric field and 50 pulses of IPEF with 20 kV/cm of electric field to the suspension that is mixed lactic acid bacteria and yeast.