Although due to their acidity some fruit juices are considered safe, several outbreaks have been reported. For processing fruit juices, microwave heating offers advantages such as shorter come-up time, faster and uniform heating, and energy efficiency. Thus, it could be a beneficial alternative to conventional pasteurization. The objective of this study was to study the inactivation kinetics of Escherichia coli O157:H7 and Salmonella Typhimurium under microwave pasteurization at temperatures between 80 and 90 °C, i.e., at conditions that are employed in conventional pasteurization. Inoculated juices were treated at different power levels (600 W, 720 W) and treatment times (5s, 10s, 15s, 20s, 25s). Time-temperature profiles were obtained by fiber-optic sensors in contact with the samples allowing continuous data collection. The log-logistic and Arrhenius equations were used to account for the influence of the temperature history; thus, resulting in two different modeling approaches that were compared in terms of their prediction abilities. Survival kinetics including non-isothermal conditions were described by a non-linear ordinary differential equation that was numerically solved by the Runge-Kutta method (ode45 in MATLAB ®). The lsqcurvefit function (MATLAB®) was employed to estimate the corresponding survival parameters, which were obtained from freshly made apple juice, whereas the prediction ability of these parameters was evaluated on commercial apple juices. Results indicated that inactivation increased with power level, temperature, and treatment time reaching a microbial reduction up to 7 Log10 cycles. The study is relevant to the food industry because it provides a quantitative tool to predict survival characteristics of pathogens at other non-isothermal processing conditions.

中文翻译：

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苹果汁的微波巴氏灭菌法：模拟大肠杆菌O157：H7和鼠伤寒沙门氏菌在80-90°C下的灭活作用。

尽管由于它们的酸度，某些果汁被认为是安全的，但已经报道了几起暴发。对于加工果汁，微波加热具有诸如缩短准备时间，加快加热速度和均匀加热以及提高能源效率等优点。因此，它可能是常规巴氏灭菌的有益替代方法。这项研究的目的是研究大肠杆菌O157：H7和鼠伤寒沙门氏菌在微波巴氏灭菌中在80到90°C之间的温度，即在常规巴氏灭菌所采用的条件下的失活动力学。接种后的果汁分别以不同的功率水平（600 W，720 W）和处理时间（5s，10s，15s，20s，25s）进行处理。通过与样品接触的光纤传感器获得时间-温度曲线，从而可以连续收集数据。使用对数逻辑和Arrhenius方程来说明温度历史的影响。因此，产生了两种不同的建模方法，并根据其预测能力进行了比较。用非线性常微分方程描述了包括非等温条件在内的生存动力学，该方程由Runge-Kutta方法（MATLAB®中的ode45）以数值方式求解。使用lsqcurvefit函数（MATLAB®）估计相应的生存参数，这些参数是从新鲜制作的苹果汁获得的，而这些参数的预测能力是在市售苹果汁中评估的。结果表明，灭活随着功率水平，温度和治疗时间的增加而增加，直至达到7 Log10循环的微生物减少。