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

Abstract

Investigation was made of the composition of milk fatty acid methyl esters (C4-C18) by means of gas chromatography employing an ionization detection system. The positions of the various methyl esters on the chromato-grams were established by using reference compounds on a nonpolar (Apiezon-L) capillary column and a relatively polar (diethylene glycoJ succinate polyester) packed column. By this means, the presence of C4, C6, and C8 through Cl8 n-alkanoic acids, the Cl6 and cis and trans C18 n-alkenoic acids, and the C18 n-alkadienoic and trienoic 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 trans-octade-cenoic acid, which progressively declined through fall and early winter. A comparison of summer and winter fat showed the entire Cl8 fraction to be increased, mainly at the expense of palmitate, 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 manufactured milk products, and its nutritional value.