Carbonyl Compounds Associated with the Off-Flavor in Spontaneously Oxidized Milk

SUIVH~ARYStudies on the carbonyl compounds in the butteroil of spontaneously oxidized whole milk indicate that the mechanism involved is typical of classic lipid autoxidation.The C~ through C~, saturated aldehydes, Co to C~ alk-2-enals, and C8 to C~ alk~2,4-dienals were tentatively identified in this product as their 2,4dinitrophenylhydrazones, on the basis of their behavior on magnesia, ultraviolet spectra, column partition chromatographic retention volumes, paper chromatographic properties, or gas chromatographic characteristics of the regenerated compounds.Flavor studies in conjunction with quantitative carbonyl analyses of 14 samples of butteroil from nonoxidized and spontaneously oxidized milks indicate that the alk-2,4-dienals, especially 2,4-decadienal, play a significant role in the off-flavor of this product, whereas the saturated aldehydes are of little significance in this respect.It is suggested that the C~ to C~ saturated aldehydes are present in fluid milk not as products of autoxidation, but rather as the result of either milk lipid synthesis or hydrolysis of plasmalogens or neutral plasn~alogens during pasteurization.