Oxymyoglobin in bovine muscle systems as affected by oxidizing lipids, vitamin E and metmyoglobin reductase activity

Oxymyoglobin and lipid oxidation were examined in low and high vitamin E (α-tocopherol) bovine M. longissimus thoracis et lumborum (LD) homogenates and in subcellular fractions of LD. Investigation of the effects of temperature (4, 22, 37C) and pH (5.5, 6.4, 7.2) on lipid and oxymyoglobin oxidation indicated that oxymyoglobin oxidation increased with increasing temperature (P ≤ 0.05) and was higher at the low pH (P ≤ 0.05). Lipid oxidation increased with temperature (P ≤ 0.05) only at pH 5.5. The inclusion of 45 μM FeCl ₃/ascorbate (1:1), at pH 5.5 and 4C, led to significant increases (P ≤ 0.05) in lipid oxidation but significant oxymyoglobin oxidation occurred only when the extent of lipid oxidation exceeded a threshold level. Oxymyoglobin and lipid oxidation were significantly lower in LD fractions derived from high vitamin E muscle compared to low vitamin E muscle. α-Tocopherol did not interact directly with oxymyoglobin to suppress oxymyoglobin oxidation but a positive unit effect of muscle α-tocopherol on metmyoglobin reductase activity was observed.