Thermal resistance of Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella in animal fat – Kinetic analysis and mathematical modeling

Authors: OZTURK, SAMET - Oak Ridge Institute For Science And Education (ORISE); Huang, Lihan; Hwang, Cheng An; Sheen, Shiowshuh - Allen

Submitted to: Food Research International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2024
Publication Date: 6/16/2024
Citation: Ozturk, S., Huang, L., Hwang, C., Sheen, S. 2024. Thermal resistance of Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella in animal fat – Kinetic analysis and mathematical modeling. Food Research International. 190:114652. https://doi.org/10.1016/j.foodres.2024.114652.
DOI: https://doi.org/10.1016/j.foodres.2024.114652

Interpretive Summary: Fats in meat and poultry products may enhance the survival of foodborne pathogens during cooking, but it is not clear how much they can protect the bacteria. This study was conducted to investigate the thermal inactivation kinetics of Escherichia coli O157:H7, Salmonella app., and Listeria monocytogenes in beef tallow. The results indicate that beef tallow could significantly enhance the survivability of these pathogens. Mathematical models were developed to assist the food industry to develop thermal processing conditions to properly destroy these pathogens in high fat meat and poultry products.

Technical Abstract: It is generally believed that animal fats in meats could increase the thermal resistance of foodborne pathogens, such as Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella. However, quantitative data are scarce concerning their thermal resistance in the presence of animal fats. Therefore, this study was conducted to evaluate the thermal resistance of these three microorganisms in beef tallow. A 4-strain cocktail of L. monocytogenes, E. coli O157:H7, or Salmonella spp. was inoculated to tallow and heated isothermally at temperatures between 55 and 80'. All survival curves did not conform to the 1st-order inactivation kinetics but 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 D values of the second stage is almost 5 times higher than those of the first stage. Such nonlinear curves were also analyzed with the Weibull model using one-step analysis, yielding < 1 exponents for the model (0.495 for L. monocytogenes, 0.362 for E. coli O157:H7, and 0.282 for Salmonella spp., suggesting increased thermal resistance with time at each temperature. L. monocytogenes appeared to be more heat-resistant than the other two in beef tallow. The results of this study suggest that these microorganisms could resist heating for longer time 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.