Mechanism of oxymyoglobin oxidation in the presence of oxidizing lipids in bovine muscle

Lipid oxidation and oxymyoglobin oxidation were measured in bovine muscle homogenates. M. longissimus dorsi homogenates (25% w/w, pH 5.7) were prepared, held at 4 degrees C, and subjected to one of the following treatments: (i) stirred and bubbled with oxygen, (ii) stirred with no oxygen, or (iii) neither stirred nor bubbled with oxygen (control). Lipid oxidation was initiated with 45 microM ferric chloride/sodium ascorbate. Lipid oxidation was highest and oxymyoglobin oxidation lowest in the homogenate bubbled with oxygen while lipid oxidation was lowest and oxymyoglobin oxidation highest in the control homogenate. Dissolved oxygen became depleted over time in the control homogenate, remained high in the homogenate bubbled with oxygen, but decreased and then increased in the homogenate stirred with no oxygen. Free radical formation was lower in the control homogenate than in the stirred homogenates as determined by spin trapping and electron spin resonance detection. The data indicated that lipid oxidation-induced oxygen depletion, as opposed to primary or secondary lipid oxidation products, is a likely cause of oxymyoglobin oxidation in muscle systems.