Trans-geometrical and positional isomers of linoleic acid including conjugated linoleic acid (CLA) in German milk and vegetable fats

A representative number of different milk fats based on a wide range of feeding and lactation conditions as well as 123 German margarines, shortenings, cooking and dietetic fats were analyzed for a variety of trans-C18:2 isomers (exhibiting at least one trans double bond) by means of gas chromatography on a 100 m Sil 88 capillary column. In milk fats contents of trans Delta 9,trans Delta 12, cis Delta 9,trans Delta 13 (+ trans Delta 8,cis Delta 12), trans Delta 8,cis Delta 13, cis Delta 9,trans Delta 12, trans Delta 9,cis Delta 12 and trans Delta 11,cis Delta 15 amounted to 0.09%, 0.11%, 0.11%, 0.10%, 0.07% and 0.33% on average and the content of total trans-C18:2 isomers (without cia Delta 9,trans Delta 11) was 0.99% in the mean. The content of conjugated linoleic acid cis Delta 9,trans Delta 11 amounted to 0.81% on average in 238 milk fats. In margarine among others the isomers trans Delta 9,trans Delta 12, cis Delta 9,trans Delta 13 (+ trans Delta 8,cis Delta 12), cis Delta 9, trans Delta 12 and trans Delta 9,cis Delta 12 were determined and quantified to 0.03%, 0.04%, 0.29% and 0.23% an average. The mean total content of trans-C18 :2 isomers in margarines was 0.61%. Moreover, for all trans-C18:2 isomers the frequency distributions as well as the correlation coefficients towards the trans-C18:1 isomers trans Delta 6 to trans Delta 16 were derived.