Some Factors Involved in the Development of Oxidized Flavor in Milk

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Abstract
Spontaneous and susceptible milks were subjected to 3 treatments; raw, pasteurized (63 C for 30 minutes) and heated (76 C for 30 minutes). The factors considered were: the effect of heat, the effect of added copper, the effect of hydrogen peroxide, the effect of sulfhydryls and the role of oxidizing enzymes in flavor development. The results of the study indicate an enzyme mechanism is involved in spontaneously oxidized flavor; whereas, a chemical oxidation is involved in induced oxidized flavor. Spontaneously oxidized flavor was prevented either by the use of heat or an enzyme inhibitor (p-chloromercuribenzoate). In contrast, these treatments had no effect upon copper induced oxidized flavor. The copper induced flavor was inhibited by the use of a copper chelating agent (2,9-dimethyl-l,10-phenanthroline) and by cysteine. Cysteine was effective in reactivating the enzyme inhibited milk, thus giving rise to the belief that an enzyme is involved in spontaneous oxidized flavor and that a sulfhydryl group is essential at the active site of the enzyme for enzymic activity.