**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** SURFACE DISCOLORATION OF FRESH BEEF DURING RETAIL DISPLAY IS A MAJOR QUALITY AND FOOD LOSS CHALLENGE IN THE MEAT INDUSTRY. CONSUMERS RELY HEAVILY ON A BRIGHT CHERRY-RED MEAT COLOR TO DETERMINE MEAT FRESHNESS, AND REJECT BEEF CUTS THAT APPEAR BROWN-RED IN COLOR. EVEN AS LOW LEVELS OF BROWN COLOR DEVELOP, CONSUMERS BEGIN TO DISCRIMINATE AGAINST DISCOLORATION AND WILL SELECT NON-DISCOLORED MEAT IF BOTH PACKAGES ARE VIEWED IN DISPLAY. AS A RESULT, THE UNSOLD BEEF PRODUCT IS DISCOUNTED (OFTEN UP TO 50%) FOR IMMEDIATE SALE, AND EVENTUALLY DISCARDED AFTER A CERTAIN TIME LIMIT. CONSERVATIVE ESTIMATES INDICATE THAT NEARLY 15 TO 20 % OF TOTAL FRESH BEEF CUTS SOLD IN U.S. RETAIL STORES IS EITHER DISCOUNTED IN PRICE OR DISCARDED DUE TO SURFACE DISCOLORATION. THE ESTIMATED ANNUAL REVENUE LOSSES DUE TO DISCOLORATION IS MORE THAN $1 BILLION IN RETAIL SALES, WHICH REPRESENTS A SEVERE LOSS IN VALUE, CONSIDERABLE FOOD WASTE, AND AN EXTREME INEFFICIENCY IN FOOD PRODUCTION AND DISTRIBUTION. THE DISCOLORATION PROBLEM IS PARTICULARLY CRITICAL FOR FRESH CUTS FROM AGED BEEF PRODUCTS. POSTMORTEM AGING, AS A VALUE-ADDING PROCESS, PLAYS A PIVOTAL ROLE IN THE ESTABLISHMENT OF BEEF PALATABILITY. NOTICEABLE IMPROVEMENTS IN EATING QUALITY, SUCH AS TENDERNESS, JUICINESS AND/OR FLAVOR, OCCUR THROUGH THE ACTION OF PROTEOLYTIC SYSTEMS INHERENT IN MEAT DURING AN EXTENDED AGING PROCESS. POSTMORTEM AGING ALSO HAS A CONSIDERABLE INFLUENCE ON INITIAL COLOR AND COLOR STABILITY OF MEAT DURING RETAIL DISPLAY. WHILE EXTENSIVE RESEARCH HAS LED TO AN IMPROVED UNDERSTANDING OF FACTORS THAT INFLUENCE MEAT COLOR STABILITY, THE UNDERLYING MECHANISM BY WHICH AGING AFFECTS OXIDATIVE STABILITY, PARTICULARLY MYOGLOBIN REDOX STABILITY, REMAINS POORLY UNDERSTOOD. THIS LEAVES A SIGNIFICANT GAP IN OUR ABILITY TO DEVELOP POST-HARVEST PRACTICES AND TECHNOLOGIES TO MITIGATE AGING-INDUCED QUALITY (OXIDATIVE) DEFECTS IN MEAT. FURTHERMORE, GIVEN THAT MEAT COLOR STABILITY IS A MUSCLE-SPECIFIC TRAIT, IT PRESENTS A CRITICAL NEED TO IDENTIFY BIOCHEMICAL MECHANISMS THAT CAN BE USED TO DEVELOP MUSCLE-SPECIFIC AGING SYSTEMS TO MINIMIZE DISCOLORATION, WHILE MAXIMIZING BENEFICIAL AGING IMPACTS ON EATING QUALITY ATTRIBUTES. WITH THE ECONOMIC IMPORTANCE OF THE IDENTIFIED NEED AND GAP TO THE U.S. BEEF INDUSTRY, SIGNIFICANT OPPORTUNITIES REMAIN TO SCIENTIFICALLY ADDRESS HOW TO CAPITALIZE ON POST-HARVEST AGING TO MAXIMIZE THE USE OF INDIVIDUAL WHOLE-MUSCLES, WHILE PREVENTING AGING-INDUCED QUALITY DEFECTS OF FRESH MEAT. THE LONG-TERM GOAL OF OUR RESEARCH PROGRAM IS TO IDENTIFY SPECIFIC BIOCHEMICAL MECHANISMS THAT CAN BE USED TO DEVELOP A BIOMARKER BASED MODEL-SYSTEM THAT PREDICT MUSCLE-SPECIFIC AGING TIME AND SUBSEQUENT QUALITY TRAITS. THIS MODEL WILL ENABLE THE OPTIMIZATION OF AGING TIME FOR MEAT PRIOR TO RETAIL DISPLAY TO MINIMIZE OXIDATION-RELATED QUALITY DEFECTS OF MEAT. TO MEET THIS LONG-TERM GOAL, WE NEED TO UNDERSTAND THE MECHANISTIC RELATIONSHIP OF DISCOLORATION WITH OXIDATIVE STABILITY OF SPECIFIC-MUSCLE TYPES ACROSS POST-HARVEST AGING STAGES. THE PROJECT DIRECTOR (PD) KIM RECENTLY GENERATED COMPELLING EVIDENCE THAT MUSCLE-SPECIFIC COMPOUNDS ASSOCIATED WITH OXIDATIVE STABILITY CAN BE IDENTIFIED USING A METABOLOMICS APPROACH. TO OUR KNOWLEDGE, WE ARE THE FIRST TO DEMONSTRATE THE USE OF METABOLOMICS TOOLS TO UNDERSTAND HOW INTRINSIC METABOLIC VARIABLES ARE ASSOCIATED WITH OXIDATIVE STABILITY AND MEAT COLOR. MOREOVER, IN A RECENT PRELIMINARY STUDY, WE FOUND THAT METABOLOMICS PROFILING OF MEAT EXUDATE CLEARLY DISTINGUISHED COMPOUNDS FROM DIFFERENT MUSCLES WITH DIFFERENT AGING PERIODS. THESE NOVEL FINDINGS ARE HIGHLY SIGNIFICANT AND WARRANT FURTHER INVESTIGATION, AND LED US TO HYPOTHESIZE THAT COMPOUNDS IN MEAT EXUDATE CAN BE UTILIZED AS NOVEL QUALITY CONTROL BIOMARKERS TO MONITOR QUALITY AND BIOCHEMICAL CHANGES OF DIFFERENT MUSCLES WITH AGING. DRIVEN BY THESE COMPELLING FINDINGS, WE PROPOSE TO FURTHER EXPLORE THE POTENTIAL OF MEAT EXUDATE AS A NOVEL/NON-INVASIVE ANALYTICAL MATRIX ON A MORE COMPREHENSIVE SCALE.OUR OVERALL OBJECTIVE IN THIS PROJECT IS TO DELINEATE THE BIOCHEMICAL MECHANISM UNDERPINNING MUSCLE-SPECIFIC AGING RESPONSE TO MEAT COLOR AND OXIDATIVE STABILITY IN ORDER TO DEVELOP A NOVEL BIOMARKER-BASED PREDICTION MODEL. OUR CENTRAL HYPOTHESIS IS THAT IDENTIFYING KEY METABOLIC COMPOUNDS IN MUSCLE TISSUE AND EXUDATE WILL PROVIDE CRUCIAL INFORMATION TO ELUCIDATE MUSCLE-SPECIFIC BIOCHEMICAL MECHANISMS. WE WILL ACCOMPLISH OUR OVERALL OBJECTIVE BY ADDRESSING THE FOLLOWING SPECIFIC OBJECTIVES. WE WILL FIRST ESTABLISH THE TEMPORAL BIOCHEMICAL CHANGES THAT OCCUR DURING MUSCLE-SPECIFIC AGING AND DETERMINE THE RELATIONSHIP TO MEAT COLOR AND OXIDATIVE STABILITY. NEXT, WE WILL CHARACTERIZE THE MAJOR METABOLITES PRESENT IN BEEF EXUDATE AND IDENTIFY KEY COMPOUNDS ASSOCIATED WITH MUSCLE-SPECIFIC COLOR STABILITY WITH AGING. TOGETHER, THE SUCCESSFUL COMPLETION OF THE PROPOSED RESEARCH WILL HAVE A SIGNIFICANT POSITIVE IMPACT IN ADVANCING KNOWLEDGE AND PROVIDING NEW POST-HARVEST AGING SYSTEMS THAT IMPROVE BEEF QUALITY AND MAXIMIZE USE OF INDIVIDUAL WHOLE-MUSCLES. THIS WILL, IN TURN, SIGNIFICANTLY AND POSITIVELY IMPACT THE PROFITABILITY AND SUSTAINABILITY OF THE U.S. MEAT/FOOD INDUSTRIES.