Alkaline hydrolysis, of glycerides

We have already seen how oils such as glyceryl trioleate form thin layers on water while soaps from the alkaline hydrolysis of glycerides form micelles. Phosphatidyl choline forms yet another structure—it spontaneously forms a membrane in water. The hydrophobic hydrocarbon chains line up together on the inside of the membrane with the hydrophilic choline residues on the outside. 

The acetone-soluble fraction was known to contain a large percentage of free fatty acids in addition to the fatty esters. Some of these fatty acids were found by Anderson to be of a type hitherto unknown. In common with the waxes, this fat did not contain any free glycerides. Alkaline hydrolysis of the fat derived from human strain bacilli yielded a water-soluble carbohydrate. This was identified as trehalose by isolation of the crystalline sugar. Corresponding fats isolated from the bovine and avian strains of bacilli were examined. The presence of glycerol could not be detected nor could the carbohydrate components be identified. 

BEC titration after alkaline hydrolysis gives glyceride sulphate Sulphate ion or liberated acidity after acid hydrolysis gives sum of ether sulphate and glyceride sulphate and hence ether sulphate (and hence sulphosuccinamate)... 

The glycerol may be united to three molecules of the same acid, or three molecules of different acids, the latter constituting a mixed glyceride. Hydrolysis may be accomplished by enzymes, such as the lipases of the alimentrary tract, by alkalies, or by superheated steam. Alkaline hydrolysis of a fat is termed saponification, because the alkali combines with the liberated aliphatic acid to form a soap. 

A third wax subfraction (soluble in both ether and alcohol) was shown to be a mixture of glycerides, carbohydrate esters of fatty acids, and true waxes. Alkaline hydrolysis gave glycerol and the carbohydrate as the water-soluble constituents. The carbohydrate yielded only inositol and D-mannose on hydrolysis with dilute mineral acid. 

Hot saponification [1,3,77—79] is the most effective tool for removing the majority of fatty material, hydrolyzing ester linkages of glycerides, phospholipids, esterified sterols, and carotenols. Moreover, alkaline hydrolysis frees boimd forms of vitamirrs (for instance, esterified and protein-bound forms) and degrades chlorophylls in water-soluble products. Also gelatine of the vitamin premix, added to supplemented... 

From the shell of A. crassipina has been isolated a sulfoquinovosylmono-glyceride, and its structure has been established by chemical splitting (alkaline methanolysis and acid hydrolysis), as well as by such physicochemical methods as H- and l3C-n.m.r. spectroscopy, g.l.c.-mass spectrometry, and field-desorption mass spectrometry.214 The major component was shown to be l-0-hexadecanoyl-3-0-(6-C-sulfo-a-D-quinovosyl)glycerol (96% of the mixture), and the minor one was its analog containing tetradecanoic acid. 

Enzymatic hydrolysis is a nondestructive alternative to saponification for removing triglycerides in vitamin K determinations. For the simultaneous determination of vitamins A, D, E, and K in milk- and soy-based infant formulas and dairy products fortified with these vitamins (81), an amount of sample containing approximately 3.5-4.0 g of fat was digested for 1 h with lipase at 37°C and at pH 7.7. This treatment effectively hydrolyzed the glycerides, but only partially converted retinyl palmitate and a-tocopheryl acetate to their alcohol forms vitamin D and phyllo-quinone were unaffected. The hydrolysate was made alkaline in order to precipitate the fatty acids as soaps and then diluted with ethanol and extracted with pentane. A final water wash yielded an organic phase containing primarily the fat-soluble vitamins and cholesterol. 

En2ymatic hydrolysis [81,82] with lipase (from Candida rugosa or from porcine pancrease) is an alternative procedure to remove glycerides in vitamin K determinations. Addition of papain (from Carica Papaya) aids the digestion of meat and foods of animal origin. The hydrolysate is first alkalinized (potassium carbonate in ethanol) to precipitate fatty acids as soaps then extracted with a water immiscible organic solvent (hexane or pentane). It has also been used in combination with supercritical fluid extraction (SEE) [83]. 

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