INACTIVATION of SACCHAROMYCES CEREVISIAE IN APPLE JUICE BY SQUARE-WAVE and EXPONENTIAL-DECAY PULSED ELECTRIC FIELDS

With equivalent electrical energy input, inactivation of microorganisms by pulsed electric fields depends on pulse waveform. Exponential-decay and square-wave pulsed electric fields were selected to treat Saccharomyces cerevisiae suspended in apple juice. A parallel-plate static treatment chamber with 25 ml volume and 0.95 cm electrode gap was used. Peak electric field and pulse electric energy input were 12 kV/cm and 260 Joules per pulse for both waveforms. Both waveforms were found effective in the microbial inactivation. However, inactivation of S. cerevisiae treated with square-wave pulses was greater than yeast treated with exponential-decay pulses. For the purpose of food pasteurization, square-wave pulsed electric fields may result in significant energy savings compared to exponential-decay pulses.