Muscle profiling improves value and optimization of beef carcasses by expanding knowledge of physical, com-positional, and marketable attributes of single-muscle cuts. Extensive profiling for individual muscle portions of the NAMI #184 beef top sirloin butt remains understudied. The objective was to compare fluid loss, objective color (L*, a*, b*), pH,and objective tenderness of the biceps femoris (BF), gluteus accessorius (GA), gluteus medius, dorsal (GMD), and gluteus medius, ventral (GMV). Beef top sirloin butts (N=70) were collected from carcasses ranging in quality grade (USDA Select and Top Choice), hot carcass weight (light≤362 kg, medium=363 to 453 kg, heavy≥454 kg), and ribeye area (REA; small≤27.8 cm2, medium=27.9 to 40.6 cm2, large≥40.7 cm2). Warner-Bratzler shear force values were the low-est for the BF and GA (P<0.001) and were significantly different than the GMD and GMV. The GA reported the lowest percentage of fluid loss in raw and cooked forms (P<0.001, P<0.001) and the highest pH (P<0.001). The GMD exhibited the highest percentage of raw purge (P<0.001), highest L* value (P<0.001), and highest shear force (P<0.001). The GMV had the highest percentage of cook loss (P<0.001). USDA Top Choice muscles were more tender than Select (P<0.001) with higher L* value (P<0.001). All 4 top sirloin muscles and muscle subunits had average peak shear force values below 3.9 kg, and thus, all were within the threshold for USDA “very tender.” These muscle profiling data will aid in identifying new beef value cuts from the top sirloin butt and assess acceptability of sirloin cuts for further retail and foodservice merchandising opportunities.

The objectives of this study were to evaluate the growth rates, carcass quality, shelf-life, tenderness, sensory characteristics, volatile compounds, and fatty acid composition of wool, hair, and composite (wool x hair) lambs. Twenty-one wether lambs [wool (Suffolk × Polypay/Targhee; n = 7), hair (Dorper × Dorper; n = 7), and composite (Dorper × Polypay/Targhee; n = 7)] were fed from weaning to finishing at the University of Idaho Sheep Center and subsequently harvested under USDA inspection at the University of Idaho Meat Lab. At 48 h postmortem, carcass measurements were taken to determine percent boneless closely trimmed retail cuts, yield grade, and quality grade. Loins were fabricated from each carcass and wet-aged at 0°C until 10 d postmortem. Following aging, 2.54-cm bone-in loin chops were cut and randomly assigned to 4 days of retail display, Warner-Bratzler Shear Force, or sensory analyses. Thiobarbituric acid reactive substances were analyzed on days 0 and 4 of retail display while subjective and objective color measurements were observed once daily. Samples (24 g) were also collected for volatile compound and fatty acid analysis. A mixed model analysis of variance was used to assess breed differences. Discernable effects were considered at P < 0.05. Wool lambs had heavier HCW (P < 0.001), larger REA (P = 0.015), and higher dressing percent (P < 0.001) than the other breeds. There was an interaction observed between breed and days of retail display for browning (P = 0.006). On day 1 chops from the composite breed had more browning than chops from the wool breed. No differences were observed between groups for lean muscle L* values (P = 0.432), a* values (P = 0.757), and b* values (P = 0.615). Differences were not observed in lipid oxidation (P = 0.159), WBSF (P = 0.540), nor consumer acceptability (P = 0.295). There were differences found for 7 of the 45 fatty acids detected and in 3 of the 67 volatile compounds detected. In conclusion, wool lambs were heavier and had a greater carcass yield than the hair lamb carcasses. Regardless of breed, consumers did not detect sensory traits that would impact their eating experience.