Application of Pulsed Electric Field for Inactivation of Yeast S. cerevisiae in Apple Juice

Abstract

Pulsed electric filed (PEF) is a non-thermal food preservation method as alternative to traditional thermal method. The effect of pulsed electric field (PEF) on inactivation of yeast Saccharomyces cerevisiae (S.cerevisiae) in apple juice containing different sugar concentration was studied. The results of this study have shown that, using PEF, the yeast could be inactivated at room temperature (20°C). The inactivation effect of PEF was dependent on pulse number, field strength, and pulse width as well as sugar concentration. Pulse numbers less than 20 pulses (at 12.6kV/cm) had no or very less effect on yeast inactivation. Increasing the pulse number up to 400 pulses resulted about 3 logs yeast inactivation. The most important factor for yeast inactivation was the field strength (10 to 30 kV/cm). Whereas, at 10.2 kV/cm and 100 pulses, less than 2 logs yeast inactivation could be achieved, was the yeast inactivation at filed strength of 30kV/cm and 100 pulses about 5 logs. At given field strength and pulse number, longer pulse width (1 to 2.5 μF) affected positively the inactivation of microorganism. In contrast, increasing the sugar concentration in apple juice higher than 20% negatively affected the inactivation of yeast during PEF treatment at given treatment conditions.