AGING AND PROCESSING AFFECT COLOR, METMYOGLOBIN REDUCTASE AND OXYGEN-CONSUMPTION OF BEEF MUSCLES

Color stability and various biochemical properties were determined in bovine longissimus dorsi and psoas major at different times postmortem (8 hr to 21 days) and during retail display. Surface metmyoglobin acc umulation, metmyoglobin reductase activity and oxygen consumption rate were affected by muscle type, postmortem aging, and fabrication metho d (p < 0.01). Psoas steaks had greater metmyoglobin accumulation, lowe r metmyoglobin reductase activity, and greater oxygen consumption than longissimus steaks. However, color stability of muscles was similar a fter grinding, which increased oxygen consumption. Color was most stab le in steaks fabricated at 4 or 7 days postmortem. The order of color stability was knife-cut steaks > saw-cut steaks > ground muscle.