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Major Free Fatty Acids in Milk

1965; Elsevier BV; Volume: 48; Issue: 12 Linguagem: Inglês

10.3168/jds.s0022-0302(65)88529-0

1529-9066

Judith Ann Bailey Kintner, E.A. Day,

Protein Hydrolysis and Bioactive Peptides

Milk and fractions therefrom were lyophilized and the powder was mixed with silicic acid, acidified, and extracted with ethyl ether in a Soxhlet extractor.The free fatty acids (FFA) extracted in this manner were isolated on an anionic exchange resin, converted to methyl esters, and analyzed by gas-liquid chromatography.The data were quantitated by use of internal standards.Most of the FFA of milk were distributed in the fat and the fat globule merebrane fraction.Milk sermn free of lipid material contained less than 10% of the FFA.Hence, milks with higher fat content contain more FFA, and milks standardized with skimmilk contain less than the original.Heating of milk had a pronounced effect upon the quantity of FFA; as heat treatments increased, the FFA decreased.Induced lipolysis caused a marked increase in FFA.In general, the FFA composition of milk, regardless of treatment, was comparable to the fatty acid composition of milk glyeerides.The free fatty acids (FFA) long have been recognized as important contributors to rancid flavor defects in dairy products.Many workers have reported measurable quantities of YEA in fresh milk, but as yet their importance in normal milk flavor is unknown.In most cases the FFA have been measured as a mixture by titration with base (6,11,12,13).Information obtained in this manner has been valuable in studying hydrolytic rancidity, but it is of limited value in assessing the importance of individual FFA in milk flavor.Progress in obtaining information about the significance of individual acids has been hindered by lack of suitable methods for isolation, separation, and quantitation.Several workers have measured individual short-chain acids (3,7,8,16), but a complete analysis of the major FFA has not been reported.The method for milk fat recently reported by Bills et ah (2) appeared applicable to milk, provided the FFA could be isolated in a solvent suitable for the ion exchange and esterifieation steps.The findings reported herein deal with adaption of the procedure of Bills et al. to FFA analysis of milk and application of the me~hod in determining the effect of various