Department of Biological Systems Engineering, Washington State University, Pullman, Washington, USA.
Department of Biological Systems Engineering, Washington State University, Pullman, Washington, USA
Appl Environ Microbiol. 2018 Apr 2;84(8). doi: 10.1128/AEM.02742-17. Print 2018 Apr 15.
spp. exhibit prolonged survivability and high tolerance to heat in low-moisture foods. The reported thermal resistance parameters of spp. in low-moisture foods appear to be unpredictable due to various unknown factors. We report here that temperature-dependent water activity (a) plays an important role in the sharply increased thermal resistance of serovar Enteritidis PT 30 and its potential surrogate NRRL B-2354. In our study, silicon dioxide granules, as carriers, were separately inoculated with these two microorganisms and were heated at 80°C with controlled relative humidity between 18 and 72% (resulting in corresponding a values for bacteria between 0.18 and 0.72) in custom-designed test cells. The inactivation kinetics of both microorganisms fitted a log-linear model (, 0.83 to 0.97). Reductions in the a values of bacterial cells exponentially increased the (the time needed to achieve a 1-log reduction in a bacterial population at 80°C) values for Enteritidis and on silicon dioxide. The log-linear relationship between the values for each strain in silicon dioxide and its a values was also verified for organic wheat flour. showed consistently higher values than Enteritidis over the a range tested. The estimated z (the change in a needed to change by 1 log) values of Enteritidis and were 0.31 and 0.28, respectively. This study provides insight into the interpretation of thermal resistance that could guide the development and validation of thermal processing of low-moisture foods. In this paper, we established that the thermal resistance of the pathogen Enteritidis and its surrogate , as reflected by values at 80°C, increases sharply with decreasing relative humidity in the environment. The log-linear relationship between the values of each strain in silicon dioxide and its a values was also verified for organic wheat flour. The results provide new quantitative insight into the way in which the thermal resistance of microorganisms changes in low-moisture systems, and they should aid in the development of effective thermal treatment strategies for pathogen control in low-moisture foods.
spp. 在低水分食品中表现出延长的生存能力和对热的高耐受性。 spp. 在低水分食品中的热抗性报告参数似乎由于各种未知因素而无法预测。我们在这里报告，依赖于温度的水活度（a）在肠炎沙门氏菌血清型 Enteritidis PT 30 及其潜在替代品 NRRL B-2354 的热抗性急剧增加中起着重要作用。在我们的研究中，二氧化硅颗粒作为载体，分别接种这两种微生物，并在 80°C 下加热，相对湿度在 18%和 72%之间（导致细菌的相应 a 值在 0.18 和 0.72 之间）在定制设计的测试单元中。这两种微生物的失活动力学都符合对数线性模型（r2，0.83 至 0.97）。细菌细胞的 a 值降低呈指数增加了在 80°C 下肠炎沙门氏菌和 NRRL B-2354 在二氧化硅上的（在 80°C 下实现细菌群体 1 对数减少所需的时间）值。在二氧化硅中每种菌株的 值与其 a 值之间的对数线性关系也通过有机小麦粉得到验证。在测试的 a 值范围内，NRRL B-2354 显示出比肠炎沙门氏菌更高的 值。肠炎沙门氏菌和 NRRL B-2354 的估计 z（a 值变化 1 对数所需的变化）值分别为 0.31 和 0.28。本研究深入了解了对热抗性的解释，这可以指导低水分食品热加工的开发和验证。在本文中，我们确定了病原体肠炎沙门氏菌及其替代品的热抗性，如 80°C 时的 值所示，随着环境中相对湿度的降低而急剧增加。在二氧化硅中每种菌株的 值与其 a 值之间的对数线性关系也通过有机小麦粉得到验证。结果为微生物在低水分系统中热抗性变化的方式提供了新的定量见解，它们应该有助于开发针对低水分食品中病原体控制的有效热处理策略。
