Ascorbic Acid Oxidation and Lipid Peroxidation in Milk

SUMMARY Ascorbic acid oxidation was studied in relation to the natural copper level and to lipid peroxidation in milks produced by cows receiving alfalfa bay or pasture. Correlations were highly significant (r = 0.79**) between ascorbic acid oxidation rate and natural copper for both alfalfa and pasture milks. The correlation between lipid peroxidation (by the TBA test) and ascorbic acid oxidation rate was very highly significant (r = 0.87***) in alfalfa milks but nonsignificant in pasture milks. Some postulated mechanisms for the action of copper and ascorbic acid in producing oxidized flavor were studied. The results do not support the theories of the role of the ascorbic acid radical, or of hydrogen peroxide, in the initiation of oxidized flavor. The kinetics of ascorbic acid oxidation by light, hydrogen peroxide, and ascorbic acid oxidase were examined. Zero‐order kinetics was found for light, and first‐order for the other agents.