Thermosonication process of sour cherries: Microbial inactivation kinetics, experimental and computational fluid dynamics simulation

Abstract

In this study, the inactivation of Listeria monocytogenes PTCC 1302 and Shigella sonnei PTCC 1974 of sour cherries by thermosonication (37 kHz, 300 W; 50and 60°C; 0–12 min) was evaluated. Several statistical models including polynomial, Weibull, and biphasic linear models were implemented to obtain the variation of microorganism population through time. The coupled non-linear Westervelt and heat transfer equations were solved to determine the acoustic pressure and thermal fields using computational fluid dynamics (CFD). According to the obtained results, average inactivation improvements of 15.47 and 17.13% were obtained when the temperature level was increased for both S. sonnei and L. monocytogenes, respectively. S. sonnei was more affected by the sonication procedure at the initial stages, while similar behavior was also found for L. monocytogenes but at the final stages. The maximum and minimum pressure level was obtained at ~380 and −230 kPa, respectively. In the beginning, the hot spot was formed near the bottom of the simulated sour cherry, where the acoustic intensity was higher. Although, with the elapse of time, the temperature field became more uniform, and the hot spot moved toward the center of the sour cherry.