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Muscles of beef, pork and chicken purchased in two seasons were analyzed for lipid oxidation potential, concentrations of total pigments, myoglobin and nonheme iron, and microsomal enzymic lipid peroxidation activity. To determine lipid oxidation potential, thiobarbituric acid (TBA) assays with antioxidant protection were conducted on raw and cooked comminuted muscles stored at 4°C. TBA values of raw chicken muscles (white and dark) and pork muscles were low and changed little during 2–6 days of storage, whereas the values of raw beef muscles were higher and increased progressively. However, TBA values of cooked muscles of all three species increased during 2–4 days of storage with no marked differences among the species. Total pigment and mycglobin concentrations best explained the differences in TBA values of stored, raw muscles among the three species.

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A calorimetric nonheme iron assay procedure for meat was modified to avoid pigment effects in determining the nonheme iron content of red meats. The modification consisted of mixing the red meat sample with NaNO* before incubation with an acid mixture to minimize the breakdown of heme pigments into nonheme iron, and inclusion of a second blank for the brownish color of the incubated liquid phase, in addition to the reagent blank.

The effects of addition of metmyoglobin (MetMb)-H202, nonheme iron (Fe2+), and the components of microsomal (or mitochondrial) enzymic lipid peroxidation system on lipid oxidation in water-extracted beef muscle residues stored at 4 °C were studied. Metmyoglobin-H202 at molar ratios ranging from 1:0.1 to 1:2 (0.26 mM MetMb with 0.026-0.52 mM H202) catalyzed the oxidation of beef muscle lipids in both raw and cooked systems. Metmyoglobin alone had little or extremely low catalytic activity. The catalytic activity of MetMb-H202 was highest at the molar ratio of approximately 1:0.25 in the raw residue system and at the molar ratio of 1:1.5 or 1:2 in the cooked system. The catalytic effect of MetMb-H202 was ascribed to "activated MetMb" and the nonheme iron released from MetMb. Activated MetMb, nonheme iron, and enzyme systems all played a major role in the catalysis of lipid oxidation in beef.