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

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Abstract
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 100m Sil 88 capillary column. In milk fats contents of trans Δ9,trans Δ12,cis Δ9,trans Δ13 (+ trans Δ8,cis Δ12),trans Δ8,cis Δ13,cis Δ9,trans Δ12,trans Δ9,cis Δ12 and trans Δ11,cis Δ15 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 cis Δ9, trans Δ11) was 0.99% in the mean. The content of conjugated linoleic acid cis Δ9,trans Δ11 amounted to 0.81% on average in 238 milk fats. In margarine among others the isomers trans Δ9,trans Δ12,cis Δ9,trans Δ13 (+ trans Δ8,cis Δ12), cis Δ9,trans Δ12 and trans Δ9,cis Δ12 were determined and quantified to 0.03%, 0.04%, 0.29% and 0.23% on 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 Δ6 to trans Δ16 were derived.