The structure of synthetic mixed triglycerides

Abstract

A study has been made of the distribution of saturated and unsaturated fatty acids in triglycerides produced synthetically by esterification of selected mixtures of saturated and unsaturated higher fatty acids with glycerol, in order to compare the general structure of these synthetic products with that of a number of natural fats. The component glycerides of many natural fats have recently been investigated in these laboratories, by converting all unsaturated groupings into acidic products by oxidation of the glycerides with anhydrous potassium permanganate in acetone solution ; only fully-saturated triglycerides present in the original fat are then left in the form of neutral compounds. This mode of attack leads primarily to a quantitative statement of the relative distribution of saturated and unsaturated acids in the glyceride molecules of a fat, but, if the combined fatty acids in the whole fat and in the fully-saturated portion are analysed in detail, and if oleic and linoleic acids (as is frequently the case) are the only unsaturated derivatives present, additional information as to the relative distribution of individual fatty acids can frequently be given. The general results of the observations on natural fats have been summed up in a recent communication in which it was shown that the glyceride structure varies with the biological type of the fat. In vegetable seed fats there is a pronounced tendency to even distribution of fatty acids throughout the glycerides ; an acid ( e. g ., oleic acid), when present in subordinate amounts, tends to become linked with about 1.3 to 1.5 molecules of an acid which is present in larger proportions and, in consequence, as between saturated and unsaturated groups, the amount of fully-saturated glyceride present in a seed fat is, broadly, determined by the amount linked with unsaturated acids in the above favoured ratio. Thus in seed fats fully-saturated glycerides do not appear in appreciable quantity until the molecular proportion of saturated fatty acids in the total fatty acid mixture reaches about 60 per cent. In contrast to seed fats, the glycerides of vegetable pericarp fats and of animal fats such as various depot fats and milks fats are constituted on more heterogeneous lines, albeit in a manner which at first sight is more akin to that which would be anticipated if the laws ordinarily operative in esterification were followed.