Determination of triglyceride composition of fats

T HE PHYSICAL PROPERTIES and performances of fats are directly related to their glyceride composition and structure. Hence knowledge of these compositional factors is important in connection with research aimed at improvement of fat-products for specific uses. Sufficient qualitative evidence was obtained by early investigators pr ior to 1900 to conelude that fats and oils in general were composed of mixtures of mixed glycerides ra ther than mixtures of simple glycerides. The first comprehensive invest igation in which chemical me thods and t e chn iques were applied in at tempts to obtain q u a n t i t a t i v e information on glyceride compos i t ion of fa t s and oils was i n i t i a t e d abou t 1927 by Hildi tch and his collaborators (13, 4, 5). Their studies have continued up to the present and have inR. W, Riemenschneider eluded numreous fats and oils of vegetable and animal origin. An extensive review of work in this field up to 1947, much of which has been done by Hildi tch and coworkers, has been published (10). The scope of this paper is restricted to a discussion of methods and techniques which are being used to determine glyceride composition. An at tempt was made to outline several concepts on glyceride distribution in na tura l fats in relation to experimental data. Tri-saturated glycerides. Probably the first method for determining tr i-saturated glycerides in fats is that of Hildi tch and Lea (13). They showed that glycerides containing unsatura ted acid radicals are oxidized to azelao-glyeerides when treated in acetone solution with excess of powdered potassium permanganate. The saturated acid radicals are not affected. Thus the oxidation of a fa t containing GS3, = GS~U, GSU=, and GU 3 would result in a product containing unchanged GS~, and GS:A, 2 GSAf, and GA3. By careful t reatment of the oxidation product with aqueous alkali the acidic azelao-glycerides can be extracted f rom the GSs, the lat ter determined simply by weight. I f any unsaturat ion remains with the GS3 portion, the fract ion is again subjected to the oxidation and extraction. The method is tedious and time-consuming, and troublesome emulsions are often encountered. Another method, based on crystallization of fats f rom acetone and application of appropria te calculations, has also been employed to advantage for determining GS3 (32, 33, 14). In this method the fract ion containing the GS3 also contains significant amounts of the most insoluble members of the GSfU. Correction for the amount of the lat ter can be made af ter