Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.
Department of Entomology, University of Minnesota, 1980 Folwell Avenue, 219 Hodson Hall, St. Paul, MN 55108, USA.
Int J Food Microbiol. 2020 Dec 2;334:108813. doi: 10.1016/j.ijfoodmicro.2020.108813. Epub 2020 Aug 3.
Low-moisture foods (LMF with water activity, a < 0.85) including pet foods and black pepper powder have consistently been associated with foodborne disease caused by Salmonella enterica. Increased heat resistance and prolonged survival at low-moisture conditions, however, remain major challenges to achieve effective inactivation of Salmonella in low-moisture foods. At low water activity (a) conditions, heat resistance of Salmonella is greatly enhanced when compared to high a conditions. This study aimed to quantify the effect of a on the heat resistance of Salmonella enterica in pet food pellets and black pepper powder. Pet food pellets were inoculated with two strains of heat resistant S. enterica and black pepper powder was inoculated with a 5-strain cocktail of Salmonella. Both inoculated food samples were equilibrated at 0.33, 0.54, and 0.75 a in controlled humidity chambers. Inoculated pet food pellets and black pepper powder in closed aluminum cells were heat treated at specific temperatures for selected times. The results showed that the Weibull model fitted well the inactivation data. At a specific temperature, the rate of inactivation increased with the increase in the a from 0.33 to 0.75, and the 3-log reduction times decreased for Salmonella in both food samples with the increase in a. Water adsorption isotherms of pet food pellets and black pepper powder at initial and treatment temperatures were developed to understand the change in a during heat treatments. The change in a during heat treatment was dependent on the type of food matrix, which possibly influenced the thermal inactivation of Salmonella in pet food pellets and black pepper powder. The quantitative analysis of heat reduction of Salmonella with respect to a aids in selection of the appropriate initial a to develop effective heat treatment protocols for adequate reduction of Salmonella in pet foods and black pepper powder.
低水分食品（水分活度 a<0.85，包括宠物食品和黑胡椒粉）一直与食源性疾病有关，这些疾病是由肠炎沙门氏菌引起的。然而，耐热性和在低水分条件下的长时间存活仍然是实现低水分食品中有效杀灭肠炎沙门氏菌的主要挑战。在低水分活度（a）条件下，与高 a 条件相比，肠炎沙门氏菌的耐热性大大增强。本研究旨在定量研究 a 对宠物食品颗粒和黑胡椒粉中肠炎沙门氏菌耐热性的影响。宠物食品颗粒接种了两株耐热性肠炎沙门氏菌，黑胡椒粉接种了五株肠炎沙门氏菌的鸡尾酒。将接种后的两种食品样品分别在控制湿度的室中平衡于 0.33、0.54 和 0.75 的 a。将接种后的宠物食品颗粒和黑胡椒粉粉末封闭在铝制细胞中，在特定温度下进行特定时间的热处理。结果表明，Weibull 模型很好地拟合了失活动力学数据。在特定温度下，随着 a 从 0.33 增加到 0.75，失效率增加，两种食品样品中肠炎沙门氏菌的 3 对数减少时间随着 a 的增加而减少。在初始和处理温度下，宠物食品颗粒和黑胡椒粉的水分吸附等温线得到了发展，以了解热处理过程中 a 的变化。a 在热处理过程中的变化取决于食品基质的类型，这可能影响宠物食品颗粒和黑胡椒粉中肠炎沙门氏菌的热失活动力学。相对于 a 对肠炎沙门氏菌的热减少的定量分析有助于选择适当的初始 a，以制定有效的热处理方案，以充分减少宠物食品和黑胡椒粉中的肠炎沙门氏菌。
