Structure and Synthesis of Milk Fat. X. Characterization of the Major Hydroxy Compounds in Milk Lipids

Lipids of fresh raw bovine and eaprine milks were extracted under mild conditions and immediately reacted with pyruvyl chloride 2,6-dinitrophenylhydrazone. The resulting derivatives were separated and isolated by column and thinlayer ehomatography. Quantification was spectrophotometrically at 402 m/x. The 1,2-diglyceride and hydroxytriglyceride fatty acids were characterized as thehmethyl esters utilizing gas-liquid chromatography. Concentrations in weight per cent of the major classes of hydroxy compomads ia the lipids of bovine herd milk were: 1,2-diglycerides 1.43 ~ .11, hydroxytriglycerides .61 ~ .05, and sterols .35 ~ .03. Lipids of individual eaprine milks yielded similar values. Following lipolytic treatment of milks from individual animals, 1,2-diglycerides tripled, whereas h~cdroxytriglycerides decreased slightly and sterols remained unchanged. During early lactation 1,fi-diglycerides and hydroxytriglycerides increased slightly whereas sterols, composed primarily of cholesterol, decreased from a high of 1.1 to 1.fl~; to a normal of .3~ in the bovine. Bovine mammary tissue Iipids were characterized by much higher levels of sterols and slightly higher levels of 1,2-diglycerides when compared with milk lipids from the same tissue. Fatty acid composition of the 1,2-diglyeerides lacked short chain fatty acids, namely butyric and eaproic acids. HydroxTtriglycerides were composed of the normal complement of fatty acids, however fewer short chain acids were evident when compared with triglycerides from the same milk.