Kinetics models for the inactivation of Alicyclobacillus acidiphilus DSM14558T and Alicyclobacillus acidoterrestris DSM 3922T in apple juice by ultrasound

In this paper, the ultrasonic inactivation efficacy of Alicyclobacillus acidiphilus DSM14558T and Alicyclobacillus acidoterrestris DSM 3922T inoculated into apple juice was investigated at power level from 200 to 600 W for treatment time from 1 to 30 min. The survival ratio of A. acidiphilus DSM14558T and A. acidoterrestris DSM 3922T decreased with the time of exposure to ultrasounds and with their power. Weibull distribution function, log-logistic model, modified Gompertz equation and biphasic linear model were used to describe the experimental data and the fitness of the models was assessed by the adjusted correlation coefficient (adj-R2) and the root mean square error (RMSE). The results showed that, for A. acidiphilus DSM14558T, the Weibull distribution function described well the characteristic of ultrasonic inactivation, while for A. acidoterrestris DSM 3922T, the adequate one was the biphasic linear model. Alicyclobacilli had a much higher resistance to ultrasonic treatments in apple juice than in buffer, which indicated that the resistance of alicyclobacilli to ultrasound varied significantly depending on their environment; A. acidoterrestris DSM 3922T, with the greatest microbial reduction of 4.56 log cycles at 600 W for 30 min, seemed more sensitive to ultrasonic treatments than A. acidiphilus DSM14558T.