High-efficiency sterilizer by high-voltage pulse using concentrated-field electrode system

Recently, a sterilization method of microorganisms in liquid food using pulsed electric fields (PEFs) has been reported by some researchers. Considering the application to the food industry, the energy efficiency of the method becomes important. It is reported that microorganisms suspended in aqueous solution were killed linearly (logarithmic) by the PEF process using a parallel-plate electrode configuration. The PEF is generated by capacitor discharge through a switch (using stationary, rotary, vacuum tube, and semiconductor, etc.). The survivability ratio decreases with increasing operating temperature and increasing capacitance value of the capacitor. Although many kinds of microorganisms suspended in liquid foods were treated by the PEF system, the energy efficiency was still low in the case of high-conductivity liquid. The authors developed a new electrode system for concentrating the electric field in a liquid food medium. The new electrode configuration made it possible to raise the energy efficiency for the pulsed sterilization process compared to that for conventional parallel-plate or concentric-cylinder electrode systems.