Evaluation of thermal process lethality for non-pathogenic Escherichia coli as a surrogate for Salmonella in ground beef

The United States Department of Agricultures' Food Safety and Inspection Service (USDA-FSIS) has developed thermal lethality guidelines for non-typhoidal Salmonella inactivation in ready-to-eat (RTE) beef and poultry, but additional means of thermal processing validation are limited. Thus, the objective of this study was to determine if non-pathogenic Escherichia coli could be used as a surrogate for Salmonella as means to validate thermal processing parameters per Appendix A. To develop thermal death time curves, ground beef at varying fat contents (5, 10, 20, 25, and 30%) was inoculated with either Salmonella or E. coli and heat treated. At 54, 57, 60, and 63 °C across all fat levels, the E. coli surrogates had significantly greater (P < .05) decimal-reduction values (D-values) than Salmonella. Beyond temperature 63 °C, regardless of fat, E. coli surrogates and Salmonella were inactivated at similar rates (P > .05). Greater reduction of E. coli surrogates in the ground beef post-lethality treatment suggest Salmonella inactivation at higher temperatures. The most appropriate use of the E. coli surrogates would be for predicting, ensuring, and validating thermal processing for Salmonella inactivation at lower temperatures. However, effects of meat product composition and processing facility variables need to be further assessed.