Determination of trans fatty acids and fatty acid profiles in margarines marketed in Spain

Two gas chromatography (GC) procedures were compared for routine analysis of trans fatty acids (TFA) of vegetable margarines, one direct with a 100-m high-polarity column and the other using argentation thin-layer chromatography and GC. There was no difference (P > 0.05) in the total trans 18:1 percentage of margarines with a medium level of TFA (similar to 18%) made using either of the procedures. Both methods offer good repeatability for determination of total trans 18:1 percentage. The recoveries of total trans isomers of 18:1 were not influenced (P > 0.1) by the method used. Fatty acid composition of 12 Spanish margarines was determined by the direct GC method. The total contents of trans isomers of oleic, linoleic, and linolenic acids ranged from 0.15 to 20.21, from 0.24 to 0.99, and from 0 to 0.47%, respectively, and the mean values were 8.18, 0.49, and 0.21%. The mean values for the ratios [cis-polyunsaturated/(saturated + TFA)] and [(cis-polyunsaturated + cis-monounsaturated)/(saturated + TFA)] were 1.25 +/- 0.39 and 1.92 +/- 0.43, respectively. Taking into account the annual per capita consumption of vegetable margarine, the mean fat content of the margarines (63.5%), and the mean total TFA content (8.87%), the daily per capita consumption of TFA from vegetable margarines by Spaniards was estimated at about 0.2 g/person/d.