Distribution of Isometric Octadecenoic Fatty Acids in Milk Fat

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Abstract
Milk fat octadecenoic acids were isolated by preparative GLC of their methyl esters and separated into cis and trans isomers by argentation TLC. The distribution of the double bonds in the 2 fractions was determined by reductive ozonolysis. cis Octadecenoic acids had double bonds in positions 6-14. The cis-9 isomer was the most abundant isomer representing .apprx. 95% of the total. trans Octadecenoic acids had double bonds in positions 6-16, the predominant isomer being trans-11 octadecenoic acid. Data illustrating the range of variation in the distribution of positional isomers of octadecenoic acid for herd milk fat and butter are presented. There was no obvious seasonal variation in the distribution pattern. Fat from perirenal and subcutaneous adipose tissue of a dairy cow had composition similar to that of butter samples.