Abstract：
The objective of this study was to evaluate the effect of fat on thermal resistance of L. monocytogenes, E. coli O157:H7, and Salmonella spp. A 4-strain cocktail of each microorganism was inoculated to beef tallow and heated isothermally at temperatures between 55 and 80℃. All survival curves did not follow the 1st-order inactivation kinetics but conformed to a two-stage linear pattern. The first stage was markedly less heat-resistant than the second, as manifested by significantly lower D values. The z values of E. coli O157 H7 and Salmonella spp. were 11.8 °C and 12.3 °C in the first stage (z1) but increased to 23.7 °C and 20.8 °C in the second stage (z2), respectively. For L. monocytogenes, while the z values were similar for both stages (z1 = 19.6 °C and z2 = 18.5 °C), the second stage D values are 3.6-5.9 times of those in the first stage. One-step analysis was used to fit the nonlinear curves to the Weibull model, yielding < 1 exponents for the model (0.495, 0.362, and 0.282, respectively, for L. monocytogenes, E. coli O157:H7, and Salmonella spp.), suggesting gradually increased thermal resistance during heating. The experimental results showed that these microorganisms could resist heating for longer time and at higher temperatures in tallow than they do in regular meats containing lower levels of fat. The kinetic models can be used to develop thermal processes to properly inactivate pathogens contaminated in the fat portions of meat products or other high fat products.
摘要：
这项研究的目的是评估脂肪对单核细胞增生李斯特菌耐热性的影响，大肠杆菌O157：H7和沙门氏菌。将每种微生物的4株混合物接种到牛脂上，并在55至80℃的温度下等温加热。所有存活曲线均不遵循一级失活动力学，而是符合两阶段线性模式。第一阶段的耐热性明显低于第二阶段，表现为明显较低的D值。大肠杆菌O157H7和沙门氏菌的z值。在第一阶段（Z1）为11.8°C和12.3°C，但在第二阶段（Z2）增加到23.7°C和20.8°C，分别。对于单核细胞增生李斯特菌，而两个阶段的z值相似（z1=19.6°C和z2=18.5°C），第二阶段D值是第一阶段的3.6-5.9倍。一步分析用于将非线性曲线拟合到Weibull模型，该模型产生<1个指数(分别为0.495、0.362和0.282，对于单核细胞增生李斯特菌，大肠杆菌O157：H7和沙门氏菌。),表明在加热过程中热阻逐渐增加。实验结果表明，与脂肪含量较低的普通肉类相比，这些微生物在牛脂中可以承受更长的时间和更高的温度。动力学模型可用于开发热过程，以适当地灭活肉类产品或其他高脂肪产品的脂肪部分中污染的病原体。
