Lactic acid and citric acid-based meat marinade effect on the survival of Shiga Toxin-producing Escherichia coli (STEC) on brisket pieces. Jayla Laday Mentor: Tamra N. Tolen, Ph.D. Department of Agriculture, Food and Animal Science College of Agriculture and Human Sciences Introduction: Shiga Toxin-producing Escherichia coli (STEC) is considered an adulterant in non-intact beef products. Through grinding or tenderizing of intact beef products, these microorganisms, that can contaminate beef surfaces can be transplanted to the inner spaces of the product and elude inactivation without proper cooking. Without cooking beef to the proper recommended internal temperature to kill the bacteria, there is a risk for the consumer to become sick. Food safety relies on a multi-hurdled approach, setting up a variety of “roadblocks” that a pathogen would have to overcome to survive. One hurdle may employ the regulation of temperature to impede the growth of the pathogen, while another may manipulate the atmosphere the product is packaged in to make the environment not suitable for pathogen survival. Another popular food safety tool is the use of organic acids to lower the pH, which is not favorable to many foodborne pathogens of concern. Organic acids like lactic acid and citric acid are an ingredient in many different products as they provide a distinct organoleptic attribute to the products they are contained in. Many acid-based meat marinades contain organic acids that help to impart flavor and even tenderize meat. The aim of this project is to evaluate the ability of meat marinades containing organic acids to lower the pH of the product and reduce STEC numbers on the surface of intact beef pieces. It is our thought that the marinade will reduce pathogen numbers on artificially contaminated beef pieces, thus improving food safety. Dr. Tolen has worked with Shiga Toxin-producing Escherichia coli through the evaluation of the usefulness of bacteriophages and lactic acid to eliminate STEC on brisket pieces and beef cattle hides. Materials and Methods: Marinade application on beef pieces: The fatty surface of beef brisket will be inoculated with STEC organisms and allowed to sit for 30 minutes to allow STEC organisms to attach to the brisket surface. Once STEC organisms are attached, five 10 cm2 pieces of brisket will be excised, weighed, and laid in a marinade of commercial lactic and citric acid solutions at varying concentrations at a ratio of 1:4 (meat: liquid) for 15h at 4°C. Following the marinating time, the excised pieces will be removed from the marinade and allowed to drip dry. The excised pieces will be stomached for one minute, serially diluted, and plated on selective agar for E. coli species. The agar plates will be incubated overnight at 37°C for 24 hours. After incubation, colonies will be counted and numbers transformed to CFU/cm2 of beef to represent surviving E. coli organisms. To evaluate the efficacy of the marinade, different concentrations will be mixed and tested against the inoculated beef pieces. The STEC organisms will be exposed to rifampicin (RIF) prior to use to produce RIF mutants that will easily plate on agar containing the antibiotic while at the same time inhibiting any background microorganisms that may be present on the meat. To determine if the marinade was effective at reducing STEC counts, statistical analysis will be used. Results and Discussion: Data collection still in progress Conclusion(s) or Summary: Conclusions have yet to be made References: Cite full references according to a standard journal in your field.
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