A Study of the Volatile Fraction Isolated from Oxidized Milk Fat. II. Further Characterization of Compounds Responsible for the Oxidized Flavor

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Abstract
Carbonyl compounds present in the volatile fraction from milk fat oxidized at 100[degree] C were hydrogenated and reacted with semicarbazide. Three classes of ketonic character were found, (1) unconjugated unsaturated (may also include saturated), (2) conjugated monene, (3) conjugated diene carbonyl compounds. Class (1) was responsible for oxidized flavor, carbonyl group and unsaturation both were essential. "Tautomers" without carbonyl absorption in the UV were indicated for classes (1) and (2). A semicarbazone of specific extinction 142.6 and melting point of 160-161[degree] C was isolated from class (2), this carbonyl compound did not contribute to the oxidized flavor. Class (3) was present in minor quantities.