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Microorganisms in low-moisture foods (LMFs) exhibit prolonged survivability and high heat resistance. Various external factors (water, food texture, nutritional compounds, etc.) influence the microbial heat resistance in LMFs; yet, the influential degree of each factor is not fully understood. In this study, the thermal resistance parameters (D and z values) of Salmonella enterica Enteritidis PT 30 (S. Enteritidis) at 80, 85, and 90 °C at the room-temperature water activity (aw, 25°C) of 0.32 ± 0.02 were measured. A series of egg powders with different fat and protein ratios (obtained by mixing egg white and yolk powders) were chosen as the model foods. Primary and secondary models were built from the isothermal inactivation kinetics of S. Enteritidis in the tested samples. The importance of fat and protein was then confirmed by controlling the water activity at the treatment temperature (aw, treatment temperature) via thermal water activity cells. The survivor curves of S. Enteritidis fitted well with the Weibull-type and log-linear models. The D values of S. Enteritidis increased with increasing fat (0-56.7%, w.b.) and decreasing protein contents (83.59-31.81%, w.b.). Incorporating the modified Bigelow model into the log-linear model yielded the zfat and zprotein of 58.96 and 57.14, respectively. At the controlled aw, 90°C of 0.32 ± 0.02, the D90°C values of S. Enteritidis increased remarkably (P < 0.05), but the values in egg white, whole egg, and egg yolk powders (11.73 ± 1.24, 23.82 ± 2.0, and 60.0 ± 2.4 min) were remarkably different. Our study identified that the influential degrees of fat, protein (zfat and zprotein values), and aw on the thermal resistance of S. Enteritidis in egg powders is in the order: aw,treatment temperature > fat > protein. Fat considerably increased the thermal resistance of S. Enteritidis even at the same aw,treatment temperature. This study quantified the effect of fat and protein on the thermal resistance of S. Enteritidis and emphasized the non-negligible effects of food components in LMFs' microbial safety. Copyright © 2022 Elsevier Ltd. All rights reserved.


Yalan Zhang, Marco E Pérez-Reyes, Wen Qin, Bin Hu, Qingping Wu, Shuxiang Liu. Modeling the effect of protein and fat on the thermal resistance of Salmonella enterica Enteritidis PT 30 in egg powders. Food research international (Ottawa, Ont.). 2022 May;155:111098

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PMID: 35400471

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