Recent trends in the fatty acid composition of German sunflower margarines, shortenings and cooking fats with emphasis on individual C16:1, C18:1, C18:2, C18:3 and C20:1 trans isomers.

In some countries the content of trans fatty acids (TFA) in margarines has strongly decreased as a result of the continuous discussion on their disadvantages regarding aspects of nutritional physiology. However, still in 1994 almost 1/3 of total fatty acids in part of German sunflower margarines, shortenings and cooking fats comprised these unfavourable TFA. In the present study the main interest was laid on trans-C16:1, trans-C18:1, trans-C20:1, trans-C18:2 and trans-C18:3 fatty acids and particularly their individual isomers, as negative metabolic activity of TFA possibly might only be attributable to certain isomers. By combining argentation thin-layer chromatography with gas chromatography using a 100-m capillary column (CP-Sil 88) trans fatty acid contents were determined in nearly all German brands of sunflower margarines (SFM; n = 9) and of cooking fats and shortenings (CFS; n = 10). Concerning the above-mentioned groups of isomers mean TFA contents of 0.01, 4.88, 0.00, 0.45 and 0.03% for SFM as well as of 0.01, 5.02, 0.03, 0.70 and 0.17% for CFS were established, respectively. The re-evaluation of samples from 1994 and 1996 exhibited that the total TFA content (sum of all mentioned isomers) in SFM decreased from 21.77% (range: 13.78-26.29; n = 11) to 5.37% (1.98-6.15%; n = 9) between 1994 and 1999. Also the total TFA content in CFS on average strongly decreased from 11.77% (0.08-33.63; n = 16) in 1994 and 12.52% (1.61-26.79%; n = 7) in 1996 to 5.91% (0.43-19.72%; n = 10) in 1999. However, even the newest CFS samples partly exhibited relative high TFA contents. In addition to the total TFA contents all positional isomers of trans-C18:1, trans-C18:2 and trans-C18:3 in SFM and CFS were quantified and compared between different years. The conjugated linoleic acid (cis delta 9, trans delta 11) occurred only in small amounts of 0.03% and 0.02% in current SFM and CFS.