ABSTRACTMyofibril fragmentation index (MFI), sarcomere length, total and soluble collagen, Warner‐Bratzler shear and sensory tenderness were determined on loin steaks from carcasses that varied in marbling, maturity and composition. Loin steaks from 72 A, 11 B, 19 C and 22 E maturity beef carcasses were removed at lo‐14 days of postmortem storage at 2°C. Steaks were double wrapped in freezer paper and stored at ‐29°C until the samples were used for analysis. MFI was significantly related to sensory tenderness scores as evidenced by the correlation coefficients of 0.66, 0.77, 0.75 and 0.71 for A, B, C and E maturities, respectively, and 0.76 for all maturities. MFI of loin steaks from A maturity were significantly different from MFI of loin steaks from B, C and E maturity carcasses. Differences in MFI among marbling groups within A maturity were found only at the lowest degree of marbling (practically devoid). There fore, it seems that MFI could be useful as a criterion of quality for A, B, C and E maturity carcasses, and especially A maturity carcasses without being significantly affected by marbling degree or carcass composition. These results further substantiate the use of myofibril fragmentation tenderness as a term to describe a state of tenderness of conventionally aged bovine longissimus muscle.