** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** FOODBORNE ILLNESS AND SPOILAGE OF MUSCLE FOODS ARE THE MAJOR FOOD SAFETY AND WASTE CHALLENGES IN THE MEAT INDUSTRY.ACCORDING TO THE U.S. CENTERS FOR DISEASE CONTROL AND PREVENTION (CDC), 40% OF FOODBORNE ILLNESS OUTBREAKS IN THE US ARE ASSOCIATED WITH CONSUMPTION OF CONTAMINATED MEAT AND POULTRY PRODUCTSRESULTING IN AN ESTIMATED 2 MILLION INDIVIDUAL CASES, COSTING THE MEAT INDUSTRY MORE THAN $5.7 BILLION ANNUALLY. ECONOMIC LOSSES DUE TO FOOD SAFETY CONCERNS IN MEAT PROCESSING ARE EXACERBATED BY LOSSES DUE TO SPOILAGE OR THE PERCEPTION OF SPOILAGE AS CONSUMERS REJECT FRESH MEAT PRODUCTS WITH BROWN-RED DISCOLORATION, STRONG OFF-ODORS, AND THE DEVELOPMENT OF SLIME. IN 2010, ABOUT 1.2 MILLION METRIC TONNES OF MEAT AND POULTRY PRODUCTS WERE DISCARDED AT THE RETAIL LEVELREPRESENTING A SEVERE LOSS IN VALUE WHILE ALSO HIGHLIGHTING EXTREME INEFFICIENCIES IN FOOD PRODUCTION AND DISTRIBUTION. THE PROBLEM IS PARTICULALRY CRITICAL FOR FRESH CUTS FROM AGED BEEF PRODUCTS. POSTMORTEM AGING IS EXTENSIVELY PRACTICED IN THE MEAT INDUSTRY TO IMPROVE EATING QUALITY ATTRIBUTES. PROLONGED AGING, HOWEVER, HAS AN ADVERSE IMPACT ON SHELF-LIFE AND OXIDATIVE STABILITY, WHICH RESULTS IN SUBSTANTIAL DEVELOPMENT OF SPOILAGE CHARACTERISTICS.CONSUMERS READILY REJECT FRESH MEAT PRODUCTS WITH RECOGNIZED SPOILAGE CHARACTERISTICS, SUCH AS BROWN-RED DISCOLORATION, STRONG OFF-ODORS, AND THE DEVELOPMENT OF SLIME. OUR OVERALL OBJECTIVE IN THIS PROJECT IS TO DELINEATE THE MICROBIAL ECOLOGY AND MECHANISMS UNDERPINNING SPOILAGE AND GROWTH OF FOODBORNE PATHOGENS IN SPECIFIC MUSCLES UNDER DIFFERENT AGING SCHEMES. OUR CENTRAL HYPOTHESIS IS THAT CHARACTERIZING METABOLIC PATHWAYS AND KEY METABOLIC COMPOUNDS IN MEAT EXUDATE WILL PROVIDE CRUCIAL INFORMATION TO ELUCIDATE MUSCLE-SPECIFIC BIOCHEMICAL MECHANISMS. THIS HYPOTHESIS HAS BEEN FORMULATED BASED UPON STRONG EVIDENCE IN OUR RECENT PILOT STUDIES, WHERE WE FOUND THAT METABOLOMICS PROFILING OF MEAT EXUDATES CLEARLY DISTINGUISHED COMPOUNDS FROM DIFFERENT MUSCLES FROM DIFFERENT AGING PERIODS AND LEVELS OF SPOILAGE. WE WILL ACCOMPLISH OUR OVERALL OBJECTIVE BY ADDRESSING THE FOLLOWING SPECIFIC RESEARCH OBJECTIVES. WE WILL FIRST ESTABLISH THE TEMPORAL BIOCHEMICAL CHANGES IN MICROBIAL COMMUNITIES THAT OCCUR DURING MUSCLE-SPECIFIC AGING UNDER SPOILAGE CONDITIONS AND IN RESPONSE TO SALMONELLA AND E.COLI O157:H7 PROLIFERATION. NEXT, WE WILL CHARACTERIZE THE MAJOR METABOLITES PRESENT IN BEEF EXUDATES AND IDENTIFY KEY COMPOUNDS ASSOCIATED WITH MICROBIAL GROWTH DURING AGING. TOGETHER, THE SUCCESSFUL COMPLETION OF THE PROPOSED RESEARCH WILL PROVIDE THE BASIS FOR THE DEVELOPMENT OF BIOMARKER-BASED SPOILAGE AND CONTAMINATION PREDICTION MODEL SYSTEMS UTILIZING SIMPLE, VALUELESS, AND EASY-TO-OBTAIN MEAT EXUDATE. THIS WILL, IN TURN, SIGNIFICANTLY AND POSITIVELY IMPACT THE PROFITABILITY AND SUSTAINABILITY OF THE U.S. MEAT/FOOD INDUSTRIES.