Fatty acid analysis, TAG equivalents as net fat value, and nutritional attributes of commercial fats and oils

The fatty acid quantities of 24 commercial fat and oil products in Finland were analyzed by capillary gas chromatography applying relative retention times of fatty acid methyl esters on two channels for identification of fatty acids. An internal standard method (C19:0 methyl ester) with methyl group and empirical fatty acid response corrections was used for quantitation of the fatty acids. GLC on a CP Sil 88 column permitted the determination of trans C16:1, C18:1, C20:1, and C22:1 positional isomers as groups. The net fat contents of fats and oils were calculated as triacylglycerol (TAG) equivalents derived from the fatty acid quantities. Ten nutritional attributes of the fats and oils based on quantitative fatty acid analysis are also presented. A recommendation is given for the use of the 10 fatty acid variables (saturated: total, C < 12, C12-C16, C18; cis-monoenes; all cis-di- and polyenes: total, n-3, n-6; other fatty acids (FAs): total, C18:1t) as nutritional attributes in evaluation of fats in foods and diets. The fatty acid composition of spreads varied significantly: total saturated from 21 to 69 wt%, cis-monoenes from 17 to 41 wt%, n-6 di- and polyenes from 1.6 to 58 wt%, and n-3 di- and polyenes from 0.3 to 5.2 wt%. The high fraction of saturated C < 12 and C12-C16 is characteristic of butter and coconut fat. The stearic acid content was rather constant. In vegetable oils total saturated varied from 5.9 to 15 wt%, cis-monoenes from 23 to 73 wt%, n-6 di- and polyenes from 11 to 65 wt%, and n-3 di- and polyenes from 0.5 to 11 wt%. There were no saturated C < 12 fatty acids or trans fatty acids. In margarines made only of vegetable oils, other FAs consisted of C18:1t isomers. When fish oil was utilized, C16:1t, C20:1t, and C22:1t isomers were also present. Butter fat containing spreads also had C18:2-conjugated and C18:2ct,tc in addition to C18:1t isomers. In spreads, the content of C18:1t isomers varied from 0 to 17 wt%. Soft margarines had a higher C18:1t content than hard margarines.