Inactivation ofEscherichia coliand Quality Changes in Black Mulberry Juice Under Pulsed Sonication and Continuous Thermosonication Treatments

Abstract

Effects of pulsed sonication and continuous thermosonication treatments on Escherichia coli ATCC 25922 inactivation in black mulberry juice were investigated at different acoustic power densities and different temperatures. The inactivation data were evaluated with five selected kinetic models with regard to adjusted correlation coefficient and root mean square error. The inactivation data of all treatments were well fitted with Weibull model followed by biphasic linear and first-order models. Treatment time for 5 log reduction of the E. coli was estimated in 14.10 min for pulsed sonication at 25C and 1.63 W/mL and 10.45 min for continuous thermosonication at 50C. Additionally, some physicochemical properties of black mulberry juices were tested for the treatments. Color and turbidity values increased, whereas monomeric anthocyanin contents decreased by the treatments. However, remarkable changes were not observed in titratable acidity, pH, percent polymeric color and antioxidant activity of black mulberry juice. Practical Applications This study demonstrates that the Weibull was the best model for estimation of ultrasonic pasteurization parameters of the black mulberry juice. Black mulberry juice could be pasteurized by the sonication treatments even at low temperatures. Because it takes a long time at low temperature, the treatment could be assisted by heat treatment at mild temperature to decrease pasteurization time. The ultrasonic treatment which led to increase in turbidity of the juice can be a potential application in juice clarification to reduce the risk of post-turbidity during storage.