Trans-isomeric fatty acids present in West German margarines, shortenings, frying and cooking fats.

Fatty acid patterns were determined in 83 brands of margarine, 9 brands of low-calorie margarine and 18 brands of shortening, frying and cooking fat purchased at random from the retail marker in the Federal Republic of Germany in 1973/1974, and a second time in 1976. As a result of gas-liquid chromatographic analyses on a Silar 10 C coated packed column, complemented in some cases by the values recorded on a highly selective SP 2340 capillary column, trans-octadecenoic acids ranging from 53.2 to 0.1% were measured. None of the products examined was completely free of trans-fatty acids. High values of trans-octadecenoate were always accompanied by positional isomers of cis-octadecenoate, by 9trans,12trans-octadecadienoate and by 9cis,12trans-octadecadienoate and 9trans,12cis-octadecadienoate. Furthermore, two mixed geometric isomers derived from linolenic acid (probably 9cis,12cis,15trans-octadecatrienoate and 9trans,12cis,15cis-octadecatrienoate) could be identified, provided that the individual brand contained sufficient linolenic acid. Following partial hydrogenation, transhexadecenoate, 0.1 to 0.2%, was detected in some of the edible fats.