Structure and Synthesis of Milk Fat. I. Gas Chromatographic Analysis

Abstract

Investigation was made of the composition of milk fatty acid methyl esters (C4-C~) by means of gas chromatography employing an ionization detection system. The positions of the various methyl esters on the chromatograms were established by using reference compounds on a nonpolar (Apiezon-L) capillary column and a relatively polar (diethylene glycol succinate polyester) packed column. By this means, the presence of C~, C~, and C~ through Cls n-alkanoic acids, the C,, and cis and trans C,s n-alkenoie acids, and the C~ n-alkadienoie and trlcnoic acids was confirmed. By selection of suitable operating conditions, it was possible to make quantitative analyses. Such analyses of milk fats collected at various seasons showed high summer levels of transoctadecenoie acid, which progressively declined through fall and early winter. A comparison of summer and winter fat showed the entire C,8 fraction to be increased, mainly at the expense of pahnitate, in the summer sample. It is felt that gas chromatography can be of much value in solving problems concerning the composition of milk fat as related to its synthesis, its properties in nmnufactured milk products, and its nutritionaI value.