EFFECTS OF ALPHA-TOCOPHEROL ON METMYOGLOBIN FORMATION AND REDUCTION IN BEEF FROM CATTLE FED SOYBEAN OR COTTONSEED MEAL DIETS

Hereford-Angus crossbred heifers were fed a cottonseed meal-based diet containing gossypol (14 mg free gossypol.kg body wt(-1).d(-1); CSM), a soybean meal-based diet (SBM), or alpha-tocopherol-supplemented diet s (4,036 IU vitamin E.heifer(-1).d(-1) for 90 d; CSM+E and SBM+E). The effects of diet on color stability and aerobic metmyoglobin reducing ability of beef longissimus lumborum (LL) and psoas major (PM) were ev aluated. The CSM containing gossypol did not affect alpha-tocopherol c oncentration, a value, or hue angle value of beef muscles obtained fr om control or vitamin E-supplemented cattle compared to their SBM coun terparts. Vitamin E supplementation increased endogenous alpha-tocophe rol concentrations and color stability in LL and PM muscles compared w ith controls from either diet (P < .05). In the aerobic metmyoglobin r educing ability study, LL and PM muscles were stored in 1%O-2:99%N-2 ( a pigment-oxidizing atmosphere) for 48 h and subsequently stored aerob ically for an additional 48 h. Within the LL, a-tocopherol supplementa tion delayed metmyoglobin formation in LL exposed to 1%O-2 (P < .05). Within the PM, no differences in metmyoglobin formation were found bet ween controls and vitamin E treatments in SBM or CSM diets. Relative a erobic metmyoglobin reduction was the same (P > .05) in LL and PM musc les within SBM or CSM diets for control and vitamin E treatments. alph a-Tocopherol did not seem to affect metmyoglobin aerobic reducing abil ity in LL and PM muscles.