Effects of animal age, marbling score, calpastatin activity, subprimal cut, calcium injection, and degree of doneness on the palatability of steaks from limousin steers.

Strip loin (longissimus lumborum), sirloin (gluteus medius) and round (semimembranosus) subprimals from 114 purebred and crossbred Limousin steers were used to identify main effects and interactions of animal age, marbling score, calpastatin activity, subprimal cut, calcium injection (5% wt/wt with a 200 mM CaCl2 solution at 48 h postmortem), and degree of doneness on the palatability of cooked beef steaks. Steaks were aged for 14 d, frozen, thawed, cooked to different internal temperature end points, visually scored for degree of doneness, sheared on a Warner-Bratzler shear machine, and evaluated by a trained taste panel. Raw and cooked steaks from carcasses of higher USDA quality grades had higher fat and lower moisture percentages (P < .05). Higher degrees of doneness resulted in lower moisture percentages (P < .05). Lower shear force values were associated with less variation in shear force. Younger slaughter age and lower calpastatin activity both resulted in greater tenderness (P < .05). Shear force was lowest between "medium rare" and "medium" and increased toward both ends of the degree of doneness scale for round and sirloin steaks; however, shear force increased linearly with degree of doneness in strip loin steaks (P < .05). Subprimal cut had the largest effect on taste panel tenderness ratings, and degree of doneness had the largest effect on taste panel juiciness ratings. The improvement in shear force due to CaCl2 injection was greater for strip loin and sirloin steaks than for round steaks (P < .05 for the interaction). Injection with CaCl2 improved all taste panel attributes. In addition, CaCl2 injection reduced the toughening effects of cooking (P < .05).