OF THESIS QUANTIFYING THE "AGING RESPONSE" AND NUTRIENT COMPOSITION FOR MUSCLES OF THE BEEF ROUNDThe objective of this study was to determine the optimal postmortem aging period and nutrient composition for Beef Value Cuts of the round. For the postmortem aging study, 40 USDA Select and 40 premium USDA Choice beef carcasses were selected from a commercial beef packing plant in Colorado over a 12-week period. The bottom and inside rounds were collected from both sides of each carcass for further fabrication into the following muscles: Adductor, Gastrocnemius, Gracilis, Pectineus, and Superficial digital flexor. Each pair of muscles was cut into seven steaks, approximately 2.54 cm in thickness, and vacuum packaged. All steaks were randomly assigned to one of the following aging periods: 2, 4, 6, 10, 14, 21, and 28 days, and placed in refrigerated storage (2°C, never frozen). Upon completion of the designated aging period, steaks were removed from storage, cooked to a peak internal temperature of 72°C, and evaluated using Warner-Bratzler shear force (WBSF). A two-way interaction was detected and Superficial digital flexor were analyzed for dry matter, moisture, crude protein, and ash percentages. All muscles were evaluated for lipid percentage and fatty acid and cholesterol composition. When quality grades were combined, all muscles fell into the "extra lean" or "lean" categories specified by USDA guidelines based on the total fat, saturated fat, and cholesterol content present in each cut. Results of this study illustrate the potential for Beef Value Cuts of the round to be sold in foodservice operations and retail stores with marketing emphasis being placed on the exceptional leanness and acceptable tenderness of these cuts.iv