Evaluation of Escherichia coli and Saccharomyces cerevisiae inactivation in sonicated pomegranate juice Alighourchi

Pomegranate fruit is a rich source of functional compounds with health promoting effects. Thermal processing significantly affects these compounds. Therefore، in this study the effect of ultrasonic as a non-thermal technology، on E. coli and S. cerevisiae of pomegranate juices has been studied. Fresh pomegranate juices of Malase Momtaze Saveh and Alak Saveh cultivars were inoculated with E. coli and S. cerevisiae and then، were sonicated using an ultrasonic processor supplied with a 19 mm diameter probe at constant frequency of 20 kHz and at amplitude levels (50، 75 and 100%) and times (0، 3، 6 and 9 min) in double wall glass vessel. The number of surviving microorganisms in samples was determined on selective media. The result showed that various intensities of ultrasound and sonication times significantly affected microbial populations (p<0. 01)، while the source of juice was not effective on the microbial count significantly. The inactivation of E. coli and S. cerevisiae cells at lower amplitude levels (50 and 75%) were ≤ 1log cycle، while a log reduction was achieved at lethal amplitude level (100%) of sonication that reduced E. coli and S. cerevisiae cells population approximately by 2log and 1. 1log in 9 min in studied juices، respectively. By suitable designing a double wall glass vessel، the evaluation of the effect of ultrasound (alone at constant temperature (25±1 °C)) on microorganisms was possible. Thus، it appears that sub-lethal temperature of ultrasonic process makes it impossible for the inactivation