The Unsaturated Fatty Acids of Milk Fat I. Methyl Ester Fractionation and Isolation of Monoethenoid Constituents
1954; Elsevier BV; Volume: 37; Issue: 4 Linguagem: Inglês
10.3168/jds.s0022-0302(54)91270-9
ISSN1529-9066
Autores Tópico(s)Food Chemistry and Fat Analysis
ResumoKnowledge of the component unsaturated fatty acids of milk fat is relatively meager.With the exception of oleic acid, which is a major constituent, the monoethenoid and polyethenoid z fatty acids occur in comparatively small amounts in milk fat (10,14).Nevertheless, because of their reactivity, they may be of considerable importance in the synthesis, nutritional value, physical and chemical properties, and deterioration of this complex fat.The present study was initiated to obtain further information concerning the isolation, identification, and configuration of the unsaturated fatty acids of milk fat.This paper describes experiments on the fractionation of methyl ester mixtures and the isolation of monoethenoid fatty acids as their methyl esters.Jack and Henderson (10) reviewed the literature on ester fractionation analysis of milk fat.Analytical data for methyl ester fractions (6, 7, 9, 10) confirm the presence of unsaturated fatty acids of lower molecular weight than oleic.Bosworth and Brown (2) isolated decenoic acid and methyl tetradecenoate from milk fat by bromination and subsequent fractional distillation of fractions containing saturated and unsaturated esters of the Same molecular weight.Brown and 0rians (4) resolved the C1_~, C14, and C16 methyl ester fractions of human milk fat by low temperature crystallization, but the application of this technique to similar methyl ester fractions prepared from milk fat of the cow has not been reported.The conventional method of preparing milk fat methyl esters for distillation requires the use of strong alkali, strong acid, and steam distillation (8, 10).Subsequent fractional distillation of the esters exposes the higher molecular weight fractions in the still pot to heating for several hours.Such treatments may change the polyunsaturated constituents originally present in the milk fat (15).Markley (12) has discussed the advantages of alkali-catalyzed methanolysis of fats over the conventional method of saponification and reesterification for the preparation of methyl esters because of the milder reaction conditions involved.Fractionation of mixtures of fatty acids or their derivatives by the formation of crystalline complexes with urea has been studied by Schlenk and Holman
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