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

Authors: REDEMANN, MORGAN - Purdue University; BRAR, JAGPINDER - Purdue University; NIEBUHR, STEVEN - Iowa State University; LUCIA, LISA - Texas A&M University; ACUFF, GARY - Texas A&M University; DICKSON, JAMES - Iowa State University; SINGH, MANPREET - Agriculture University Of Georgia

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2017
Publication Date: 12/20/2017
Citation: Redemann, M.A., Brar, J., Niebuhr, S.E., Lucia, L.M., Acuff, G.R., Dickson, J.S., Singh, M. 2017. Evaluation of thermal process lethality for non-pathogenic Escherichia coli as a surrogate for Salmonella in ground beef. LWT - Food Science and Technology. 90:290-296.

Interpretive Summary: The United States Department of Agriculture Food Safety and Inspection Service (FSIS) has guidelines for inactivation of Salmonella in ready-to-eat beef and poultry products, but additional means of thermal processing validation are limited. This study was conducted to determine if non-pathogenic Escherichia coli (E. coli) could be used as a surrogate for Salmonella as means to validate thermal processing parameters not detailed in the FSIS guidelines. To determine the efficacy of E. coli as a non-pathogenic surrogate, ground beef at varying fat contents was inoculated with either Salmonella or E. coli and heat treated at various temperatures. At lower inactivation temperatures the Salmonella was more sensitive to killing than E. coli surrogates, but at higher temperatures, the E. coli surrogates and Salmonella were inactivated at similar rates. Thus these E. coli surrogates can be successfully used to determine Salmonella inactivation in RTE meats products. The use of non-pathogenic E.coli surrogate organisms present an opportunity to validate thermal processing without compromising food safety at a processing facility.

Technical Abstract: The United States Department of Agriculture 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 deg C across all fat levels, the E. coli surrogates had significantly greater (P < .05) decimal-reduction values (D-values) than Salmonella. Beyond temperature 63 deg 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.