Thermal Inactivation of Listeria Monocytogenes in Ground Beef Under Isothermal and Dynamic Temperature Conditions

Authors: Huang, Lihan

Submitted to: Journal of Food Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2008
Publication Date: 7/19/2008
Citation: Huang, L. 2008. Thermal Inactivation of Listeria Monocytogenes in Ground Beef Under Isothermal and Dynamic Temperature Conditions. Journal of Food Engineering. 90:380-387.

Interpretive Summary: Thermal processing is one of the most widely used technologies for food preservation. The current mathematical model is not suitable for designing and evaluating thermal processes to kill Listeria monocytogenes (a potentially lethal pathogen) in ground beef, and can lead to underestimation of bacterial survival. The objective of this research was to develop a new and more accurate mathematical approach to describe thermal inactivation of Listeria monocytogenes in ground beef. The new method can be used to ensure the safety of cooked ground beef.

Technical Abstract: The objective of this research was to compare the suitability of three kinetic models for describing the survival of Listeria monocytogenes in ground beef under both isothermal and dynamic temperature conditions. Ground beef (93% lean), inoculated with a 4 strain cocktail of L. monocytogenes, was subject to heating at 57, 60, 63, or 66 deg C to develop isothermal kinetic models. Experimental data showed that the isothermal survival curves were not strictly linear and were downwardly concaved. The isothermal inactivation of L. monocytogenes in ground beef was better described by two nonlinear kinetic models, the Weibull-type and the modified Gompertz models. Analytical results showed that the square root of the mean squared error (RMSE) of the Weibull-type and the modified Gompertz models were 0.19 and 0.20 log(CFU/g), both significantly smaller than that of the linear model (0.48 log(CFU/g)). Under linear heating dynamic conditions, however, only the modified Gompertz model, with a RMSE of only 0.71 log(CFU/g), was suitable for describing the survival of the pathogen. Both linear and Weibull-type models grossly underestimated the survival of L. monocytogenes in ground beef during dynamic heating.