A Proposed Salmonella Risk Assessment And Scoring Tool Based On Microbiological Test Results Of Boneless And Ground Beef Purchased For The United States National School Lunch Program, October 2013 To June 2019

Abstract

The purpose of this thesis is to contribute to the science of food safety by thoroughly evaluating results of United States Department of Agriculture, Agriculture Marketing Service (AMS) microbiological testing results for boneless and ground beef produced between October 2013 and July 2017. The thesis is the result of asking three research questions about the AMS data: 1) what is the relationship between indicator microorganism concentrations and pathogen presence, 2) how might these associations differ among different serotypes and Salmonella serotype Dublin in particular, 3) can a simplified scoring system be developed using combinations of indicator microorganisms concentrations in order to assess risk of Salmonella presence in boneless and ground beef lots? Three studies were conducted to answer these research questions. In Chapter 1, AMS microbiological testing results for school years 2015 through 2018 were described and compared to past results for school years 2011 through 2014. In Chapter 2, an investigation into Salmonella Dublin’s unique and confounding relationship with indicator microorganism concentrations is described. In Chapter 3, an innovative composite indicator scoring system is presented and used to evaluate risk of Salmonella detection in boneless and ground beef lots. I conclude that: 1) AMS beef is produced under hygienic and safe conditions with few instances of exceeding indicator organisms limits or documentation of pathogen presence, 2) future use and research with indicator microorganisms must consider underlying Salmonella serotype prevalence within the source cattle population, and 3) beef abattoirs, regulators, and purchasers may consider and benefit from adapting the proposed indicator scoring system to supplement their existing quality control systems.