Further Studies on the Determination of the 2‐Isomers of Triglycerides from Natural Fats

A method of determination of the 2‐isomers of mixtures of triglycerides is proposed in this paper. This method has been applied to one class of triglycerides of peanut oil, fractionated by Argentation Thin‐Layer Chromatography (Ag+‐TLC), namely the class 012 (one saturated, one mono‐ and one diunsaturated fatty acid in the molecule), The calculation takes into account as experimental data, besides the fatty acid composition of monoglycerides issued from lipolysis by pancreatic lipase, the fatty acid composition of one class of diglycerides, fractionated by Ag+‐TLC, either 01 or 02. It is shown that this method can be utilized even when the total diglycerides, issued from lipolysis, are not completely representative of the original triglycerides, due to preferential hydrolysis of unsaturated fatty acids at external positions of glycerol. As a matter of fact, the fatty acid composition of the different classes of diglycerides is not modified by this specific hydrolysis. Only is altered the relative proportion of the various classes of diglycerides. But the calculation utilized the proportion the class should have in the case of a non‐preferential hydrolysis. It is easily calculated from the fatty acid composition of the mono‐glycerides. Thus only the monoglycerides formed during lipolysis have to be representative of the original triglycerides. Resolution of a system of equations derived from the composition of monoglycerides and of one class of diglycerides (01) or the other one (02) has permitted the nature and the proportion of eighteen 2‐isomers of the triglycerides 012 from peanut oil, to be precisely determined. The results show that the 2‐position of glycerol is, in all cases, preferentially occupied by linoleic acid, and then by oleic acid. In this class of tri glycerides (012) palmito‐linoleo‐olein (16:0 ‐ 18:2 ‐ 18:1) re presents 37.2%, that is 5.2% of total peanut oil triglycerides.