Factors influencing the variation in tenderness of seven major beef muscles from three Angus and Brahman breed crosses

Beef carcasses (n=30) from 3/4 Angus (A)×1/4 Brahman (B), 1/4A×3/4B, and 1/2A×1/2B F(1) crosses were used to evaluate breed type, electrical stimulation, and postmortem aging on the M. semimembranosus (SM), M. semitendinosus (ST), M. biceps femoris (BF), M. vastus lateralis (VL), M. gluteus medius (GM), M. longissimus dorsi lumborum (LD), and M. triceps brachii (TB). Shear force values decreased with increased postmortem aging to a greater extent in steaks from 3/4A×1/4B than steaks from the other breed types. Shear force values for steaks from the round (SM, ST, BF, VL) were higher than steaks from the loin (LD, GM) and chuck (TB) for both electrically stimulated and non-electrically stimulated muscles. In the LD muscle, calpastatin activities were similar among breed types. Muscle type played the greatest role in determining tenderness.