New Horizons of Science, Technology and Culture Vol. 11

Although conventional thermal pasteurisation assures the safety of food products, it can also negatively affect sensorial acceptance. Therefore, alternative pasteurisation processes are intensively investigated. The application of electrical fields to biological cells induced electrical charges on the cell membrane. Pulsed electric field (PEF) is a non-thermal food preservation method as an alternative to the traditional thermal method. The effect of pulsed electric field (PEF) on the inactivation of yeast Saccharomyces cerevisiae (S. cerevisiae) in apple juice containing different sugar concentrations 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 12.6 kV/cm) had no or very little effect on yeast inactivation. Increasing the pulse number up to 400 pulses resulted in about 3 logs of 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 a given field strength and pulse number, a longer pulse width (1 to 2.5 µF) affected the inactivation of microorganisms positively. In contrast, increasing the sugar concentration in apple juice to higher than 20% negatively affected the inactivation of yeast during PEF treatment at given treatment conditions. The study concluded that PEF treatment is a suitable non-thermal method for the inactivation of liquid foods.