Influence of Postmortem Aging Period on the Fragmentation Index of Bovine Longissimus Muscle

ABSTRACT A total of 59 short loins were aged at 2°C for 60, 120, 180, and 240 hr postmortem PM). Following each aging period, steaks were removed for shear force value (SFV) and fragmentation index (FI) measurements. One steak was removed at 60 hr PM for chemical determination. FI was significantly related (r=0.30‐0.63) to SFV in 32 comparisons. Variation in FI and SFV for PM aging period and residue fraction drying time (0 and 10 min) was not significant; thus, FI can be accurately determined by omission of the 10 min residue fraction drying time. FI determined on bovine longissimus muscle at 60 hr PM was related (P < 0.05) to SFV of cooked loin steaks from loins aged 60, 120, 180, and 240 hr PM. FI determined at 120, 180 or 240 hr was also related (P < 0.05) to SFV of loin steaks. Simultaneous consideration of five carcass traits (marbling degree, lean color, lein firmness, fat thickness, and carcass weight) accounted for approximately 10% of the observed variation in SFV for cooked steaks from loins aged 60–240 hr, while FI accounted for an additional 15–42%. These data indicate that SFV of cooked loin steaks from A maturity carcasses can be predicted to a significant degree by FI of law muscle determined at 60 hr PM.