The chemical constitution of natural fats.

The purpose of this communication is to give a brief summary of the composition of the natural fats which come within the scope of a discussion upon the subject of triglyceride fats in human nutrition. This will be done by considering, first, typical compositions of human and other ,mammalian fats (depot, liver and milk) and, subsequently, the compositions of the vegetable and marine animal fats which are most commonly utilized as sources of human dietary fat. To describe these fats in terms of their constituent mixed glycerides would be too complex and lengthy; fortunately this is unnecessary for the present purpose. All natural fats are complicated mixtures of mixed glycerides, but each individual mixed triglyceride is, in nearly all instances, elaborated according to the operation of a simple principle, often referred to as ‘even’ or ‘widest’ distribution of the fatty acid groups between the glycerol molecules. This prevailing type of glyceride structure may be briefly described (Hilditch, 1947, p. 16) by saying that as soon as a given fatty acid forms about 35% of the total fatty acids in a fat it will occur at least once in every triglyceride molecule of the fat, and that no simple triglycerides containing three groups of the same fatty acid will occur until such acid forms nearly two-thirds, or more than two-thirds, of the total fatty acids. Each fatty acid, moreover, acts independently of the rest in competing for union with glycerol according to this general plan. This general rule, most clearly recognizable in the comparatively few natural fats which contain only two or three major component acids, has been found, with very few exceptions, to hold throughout the vegetable and animal kingdoms. In two classes of animal fats only does it fail accurately to describe the general glyceride structure of natural fats : animal depot fats which are unusually rich in mixed glycerides containing stearic groups, and milk fats in which the lower saturated acids from butyric to lauric are markedly prominent. In these classes it has been suggested (Hilditch, 1947, pp. 302, 304) that the specific glyceride types present are the result of biochemical modification of an original preformed mixture of glycerides (chiefly palmito-oleins) assembled on the usual ‘evenly distributed’ basis.

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Spectrophotometric methods of analysis for the polyunsaturated constituents of oils and fats have been carefully restandardized for several conditions of alkali-isomerization, using purified methyl esters of linoleic, linolenic, and arachidonic acids prepared by physical rather than by chemical means A number of vegetable oil and animal fat samples were subjected to spectrophotometric analysis, and the results based on natural and on bromination-debromination fatty acid standards were compared The natural fatty acid standards lead to significantly higher accuracy and their use in the spectrophotometric analysis of natural fatty materials is strongly recommended Results obtained under different conditions of isomerization were in satisfactory agreement An isomerization time of 45 minutes is recommended rather than 25 or 30 minutes The glycerol-air technique is preferred for general use because of its simplicity and high precision The ethylene-glycol-nitrogen technique is a close second choice because of the greater transparency of reagent blanks

Standardization of spectrophotometric methods for determination of polyunsaturated fatty acids using pure natural acids

The component fatty acids of the seed fats of Moringa pterygosperma and Moringa concanensis have been investigated by using the techniques of urea-adduct segregation and quantitative paper chromatography. The present analysis indicates the percentage composition of the mixed fatty acids to be: palmitic 3.1, 11.7; stearic 8.0, 3.8; arachidic 7.8, 2.4; behenic 3.5, 4.1; lignoceric 5.8, 0.6; oleic 71.0, 75.5 and linoleic 0.8, 0.9% respectively.



Untersuchungen uber die Zusammensetzung des Fettes der Moringaceae Samen



Die Fettsaure-Zusammensetzung des Samenfettes von Moringa pterygosperma und Moringa concanensis wurde nach der Harnstoff-Addukt-Fraktionierung und quantitativen Papier-Chromatographie untersucht. Die Gesamtfettsauren der M. pterygosperma bzw. M. concanensis enthielten 3.1 bzw. 11.7% Palmitin-, 8.0 bzw. 3.8% Stearin-, 7.8 bzw. 2.4% Arachin-, 3.5 bzw. 4.1% Behen-, 5.8 bzw. 0.6% Lignocerin-, 71.0 bzw. 75.5% Ol- sowie 0.8 bzw. 0.9% Linolsaure.

Studies on the Seed Fat Composition of Moringaceae family

Existing ultraviolet spectrophotometric methods have been modified for application primarily to the detection and estimation of low proportions of conjugated and nonconjugated unsaturated constituents in fats, oils, and soaps The method is applicable also to fatty materials having high proportions of these constituents Modifications include corrections for absorption by interfering substances, use of alkaline glycerol as an isomerization medium in the analytical procedure, and correction of absorption data on the isomerized product for absorption by conjugated constituents in the material before isomerization The presence of small proportions of highly unsaturated conjugated and nonconjugated compounds is established in lards, tallows, tallow soaps, and highly purified esters and acids Tall oil fatty acids are shown to contain approximately 10% of conjugated diene acids and a small amount of linolenic acid

T. P. Hilditch

Papers

The spectrographic determination of linoleic, linolenic and elaeostearic acids