Effects of a-Tocopherol on Metmyoglobin Formation and Reduction in Beef from Cattle Fed Soybean or Cottonseed Meal Diets1

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 a-tocopherolsupplemented diets (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 evaluated. The CSM containing gossypol did not affect a-tocopherol concentration, a* value, or hue angle value of beef muscles obtained from control or vitamin E-supplemented cattle compared to their SBM counterparts. Vitamin E supplementation increased endogenous a-tocopherol concentrations and color stability in LL and PM muscles compared with controls from either diet ( P < .05). In the aerobic metmyoglobin reducing ability study, LL and PM muscles were stored in 1%O2:99%N2 (a pigment-oxidizing atmosphere) for 48 h and subsequently stored aerobically for an additional 48 h. Within the LL, a-tocopherol supplementation delayed metmyoglobin formation in LL exposed to 1%O2 ( P < .05). Within the PM, no differences in metmyoglobin formation were found between controls and vitamin E treatments in SBM or CSM diets. Relative aerobic metmyoglobin reduction was the same ( P > .05) in LL and PM muscles within SBM or CSM diets for control and vitamin E treatments. a-Tocopherol did not seem to affect metmyoglobin aerobic reducing ability in LL and PM muscles.