Skip to main content
ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Microbial and Chemical Food Safety » Research » Publications at this Location » Publication #426402
Research Project: Advanced Methods for Predictive Modeling of Bacterial Growth and Survival in Foods

Location: Microbial and Chemical Food Safety

Title: Thermal inactivation kinetics of Listeria moncytogenes in fat/water emulsions and fat tissue - effect of fat content

Author
item OZTURK, SAMET - Oak Ridge Institute For Science And Education (ORISE)
item Huang, Lihan
item Hwang, Cheng An
item Sheen, Shiowshuh

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2025
Publication Date: 9/6/2025
Citation: Ozturk, S., Huang, L., Hwang, C., Sheen, S. 2025. Thermal inactivation kinetics of Listeria moncytogenes in fat/water emulsions and fat tissue - effect of fat content. Food Microbiology. 134. https://doi.org/10.1016/j.fm.2025.104921.
DOI: https://doi.org/10.1016/j.fm.2025.104921

Interpretive Summary: Fat can significantly increase the heat resistance of foodborne pathogens. This study was conducted to investigate the effect of different beef fat contents in fat/water emulsions and beef trim fat on thermal resistance of Listeria monocytogenes. The results showed that high fat contents may provide protection to foodborne pathogens, allowing them to survive normal cooking conditions designed for low fat foods. Kinetic models were developed to describe the effect of fat and temperature on the survival of L. monocytogenes in fat/water emulsions during thermal processing. The results of this study may be used by the food industry to design thermal processing conditions to properly inactivate foodborne pathogens in high fat foods.

Technical Abstract: Significant increase in thermal resistance of Listeria monocytogenes has been observed in purified beef tallow. However, how different fat levels in fat emulsion affects bacterial survival has not been evaluated. This study aimed to evaluate the effect of fat levels in solid fat/water (SF/W) emulsions on thermal resistance of L. monocytogenes. SF/W emulsions, containing 0, 25, 50, 60 and 75% of tallow by weight, were prepared by mixing tallow with soybean lecithin and Tween 80 in 0.1% peptone water in an ultrasonic processor. A 4-strain cocktail of L. monocytogenes was inoculated to the emulsions and subjected to heating at 55, 57.5, 60, 62.5, or 65 ' to observe bacterial survival. The survival curves were analyzed with the USDA IPMP-Global Fit to estimate the kinetic parameters and evaluate thermal resistance. Linear survival was observed in emulsions with fat below 50%. However, increased thermal resistance, evidenced by the increasing D and z values with the fat content, was observed. For example, the average D values at 60 ' are 0.54, 1.04, and 2.53 min, respectively, with 0, 25, and 50% fat. For emulsions with 60 and 75% fat and in beef trim fat (BTF, 86.9%), the survival curves became convexly nonlinear, which were fitted to the Weibull model. The exponents of the Weibull model range between 0.45 and 0.456, suggesting almost identical convexity of the survival curves. The convex survival curves indicate initial sensitivity to heat but the resistance increases with time at each temperature. The estimated time to a 5-log reduction becomes 11.9 and 26.4 min in 60 and 75% SF/W, respectively, and 36.5 min in BTF at 60 '. The study demonstrates the effect of different fat levels on thermal resistance of L. monocytogenes in SF/W and tissues. The results of this study may help the food industry to properly kill L. monocytogenes in fat-containing meat products.