Integration of production and postmortem technologies for improvement of USDA select grade beef

Improvement of USDA Select cattle quality is essential for consumer acceptance of leaner meat. Most of the work related to meat quality has, however, targeted USDA Choice cattle and, in most cases does not integrate animal production and postmortem technologies. Two production (animal breed and diet) factors and two postmortem technologies (electrical stimulation and carcass chilling rate), each in two levels, were studied. Meat quality was assessed in terms of tenderness and its associated variables in the longissimus and triceps muscles, and for flavor stability and cooking performance in precooked triceps muscle. Tenderness was evaluated using postrigor cooked longissimus and prerigor cooked triceps muscles. Variables measured associated with tenderness included collagen-related (concentration, solubility and thermal shrinkage temperature) and myofibrillar-related attributes (sarcomere length and myofibrillar fragmentation index). Deep round and triceps temperature evolution, and triceps pH development post-mortem were recorded. Flavor stability was assessed as TBA values. Cooking performance included cooking yield and drip loss. Carcass parameters were measured and quality and yield grades determined. Results indicated that longissimus muscle tenderness was not affected by breed, diet, electrical stimulation or chilling rate. Triceps muscle tenderness was not affected by breed and the effect of the remaining factors was inconsistent between experiments. Flavor stability was not affected by breed or electrical stimulation but medium-energy diets consistently yielded better results than high-energy diets. Cooking performance was not affected by any of the factors studied. Muscle temperatures were consistently higher in large-frame cattle and in slow chilling treatments. They were not influenced by diet or electrical stimulation. Triceps pH development was not affected by any of the factors analyzed. Large frame steers needed more days on feed to attain similar yield grade, yielded higher live and carcass weights and presented lower fat depth, quality and yield grades. Diet affected carcass weight, fat depth, marbling and quality grade, with high energy diets producing higher values for each of these parameters. Interactions were inconsistent between treatments