Department of Agricultural and Biological Engineering, Purdue University, ABE Building, 225 S. University Street, West Lafayette, IN, 47907, USA.
Department of Food Science, Purdue University, Philip E. Nelson Hall of Food Science, 745 Agriculture Mall Drive, West Lafayette, IN, 47907, USA.
Food Microbiol. 2020 May;87:103382. doi: 10.1016/j.fm.2019.103382. Epub 2019 Nov 18.
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 Log 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.
虽然由于其酸性，一些果汁被认为是安全的，但仍有几起暴发事件报告。对于果汁加工，微波加热具有升温时间短、加热更快更均匀、节能等优点。因此，它可能是传统巴氏杀菌的有益替代方法。本研究的目的是研究大肠杆菌 O157:H7 和鼠伤寒沙门氏菌在 80-90°C 微波巴氏杀菌下的失活动力学，即传统巴氏杀菌中使用的条件。接种的果汁在不同的功率水平（600 W、720 W）和处理时间（5s、10s、15s、20s、25s）下进行处理。通过与样品接触的光纤传感器获得时间-温度曲线，实现连续数据采集。对数逻辑和阿仑尼乌斯方程用于解释温度历史的影响；因此，产生了两种不同的建模方法，从预测能力方面进行了比较。生存动力学包括非等温条件，通过数值求解常微分方程（ode45 在 MATLAB ®）来描述。lsqcurvefit 函数（MATLAB®）用于估计相应的生存参数，这些参数是从新鲜的苹果汁中获得的，而这些参数的预测能力则在商业苹果汁上进行了评估。结果表明，失活率随功率水平、温度和处理时间的增加而增加，达到了 7 个对数循环的微生物减少。本研究与食品工业相关，因为它提供了一种定量工具来预测其他非等温加工条件下病原体的生存特征。
