Abstract：
Thermal processing is a widely used method to ensure the microbiological safety of milk. Predictive microbiology plays a crucial role in quantifying microbial growth and decline, providing valuable guidance on the design and optimization of food processing operations. This study aimed to investigate the thermal inactivation kinetics of Listeria monocytogenes in milk under both isothermal and dynamic conditions. The thermal inactivation of L. monocytogenes was conducted under isothermal and non-isothermal conditions in sterilized and pasteurized milk, with and without background microbiota, respectively. Furthermore, a secondary model was developed between the shoulder effect and temperature, which was then integrated into the dynamic model. The results showed that L. monocytogenes grown in Tryptic Soy Yeast Extract Broth (TSBYE) prior to thermal inactivation exhibited higher heat resistance compared to cells grown in sterilized milk at isothermal temperatures of 60.0, 62.5, and 65℃. Moreover, the presence of background microbiota in milk significantly enhanced the heat resistance of L. monocytogenes, as evidenced by the increased D-values from 1.13 min to 2.34 min, from 0.46 min to 0.53 min, and from 0.25 min to 0.34 min at 60.0, 62.5, and 65 °C, respectively, regardless of whether the background microbiota was inactivated after co-growth or co-inactivated with L. monocytogenes. For non-isothermal inactivation, the one-step dynamic model based on the log-linear with shoulder model effectively described the microbial inactivation curve and exhibited satisfactory model performance. The model developed contributes to improved risk assessment, enabling dairy processors to optimize thermal treatment and ensure microbiological safety.
摘要：
热处理是一种广泛使用的方法，可确保牛奶的微生物安全性。预测微生物学在定量微生物生长和衰退中起着至关重要的作用。为食品加工操作的设计和优化提供有价值的指导。本研究旨在研究牛奶中单增李斯特菌在等温和动态条件下的热灭活动力学。在等温和非等温条件下，在灭菌和巴氏杀菌的牛奶中进行单核细胞增生李斯特菌的热灭活，有和没有背景微生物群，分别。此外，在肩部效应和温度之间建立了一个二级模型，然后将其集成到动态模型中。结果表明，与在等温温度为60.0、62.5和65℃的灭菌牛奶中生长的细胞相比，在热灭活之前在胰蛋白酶大豆提取物肉汤（TSBYE）中生长的单核细胞具有更高的耐热性。此外，牛奶中背景微生物群的存在显着增强了单核细胞增生李斯特菌的耐热性，正如D值从1.13min增加到2.34min所证明的那样，从0.46分钟到0.53分钟，在60.0、62.5和65°C下从0.25分钟到0.34分钟，分别,无论背景微生物群是否在共同生长后被灭活或与单核细胞增生李斯特菌共灭活。对于非等温失活，基于对数线性肩模型的一步动态模型有效地描述了微生物灭活曲线，并表现出令人满意的模型性能。所开发的模型有助于改进风险评估，使乳制品加工商能够优化热处理并确保微生物安全。
