Glycerides hydrolysis

The making of soap is one of the oldest of chemical syntheses. (It is not nearly so old, of course, as the production of ethyl alcohol man s desire for cleanliness is much newer than his desire for intoxication.) When the German tribesmen of Caesar s time boiled goat tallow with potash leached from the ashes of wood fires, they were carrying out the same chemical reaction as the one carried out on a tremendous scale by modern soap manufacturers hydrolysis of glycerides. Hydrolysis yields salts of the carboxylic acids, and glycerol, CH2OHCHOHCH2OH. 

The lipase-catalysed reactions of glyceride hydrolysis and synthesis are reversible. Thus, if the water content of the reaction system is limited, the non-specific enzyme results in random interesterification but the 1,3-specific enzyme and the fatty acid-specific enzyme can be used to introduce desirable fatty acids into the triglyceride molecule and to produce preferred positional fatty acid arrangements in the triglyceride molecule. 

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. 

The term fat is applied to solid esters of fatty acids with glycerol (glycerides) if the fat is liquid at the ordinary temperature, it is conventionally called a fatty oil, vegetable oil or animal oil. The acids which occur most abundantly are palmitic ticid CH3(CHj),4COOH, stearic acid CH3(CH2)isCOOH and oleic acid CH3(CH2),CH=CH(CH2),C00H. Upon hydrolysis, fats yield glycerol and the alkali salts of these acids (soaps) ... 

Sulfated Natural Oils and Fats. Sulfated natural triglycerides were the first nonsoap commercial surfactants introduced in the middle of the nineteenth century. Since then sulfates of many vegetable, animal, and fish oils have been investigated (see also Fats AND FATTY oils). With its hydroxyl group and a double bond, ricinoleic acid (12-hydroxy-9,10-octadecenoic acid) is an oil constituent particularly suited for sulfation. Its sulfate is known as turkey-red oil. Oleic acid is also suited for sulfation. Esters of these acids can be sulfated with a minimum of hydrolysis of the glyceride group. Polyunsaturated acids, with several double bonds, lead to dark-colored sulfation products. The reaction with sulfuric acid proceeds through either the hydroxyl or the double bond. The sulfuric acid half ester thus formed is neutralized with caustic soda ... 

Discussion. For oils and fats, which are esters of long-chain fatty acids, the saponification value (or number) is defined as the number of milligrams of potassium hydroxide which will neutralise the free fatty acids obtained from the hydrolysis of 1 g of the oil or fat. This means that the saponification number is inversely proportional to the relative molecular masses of the fatty acids obtained from the esters. A typical reaction from the hydrolysis of a glyceride is ... 

S (2)-hydroxy-3-butenenitrile from acrolein and HCN trans hydrocyanation using, for instance, acetone cyanohydrin Hydrolysis of nitriles to amides, e.g. acrylonitrile to acrylamide Isomerization of glucose to fructose Esterifications and transesterifications Interesterify positions 1 and 3 of natural glycerides Oxidation of glucose to gluconic acid, glycolic acid to glyoxalic acid... 

The soaps are in all probability not produced during emulsification by hydrolysis of the glycerides but from impurities present in the oils, since olive oil may be prepared in sufficient purity as not to be affected by the addition of caustic soda the following figures being obtained by Donnan (Zeit. Phys. Ghem. XXXI. 42,1899) for the drop numbers of purified and ordinary olive oil in water and caustic soda. 

Butyric acid is a carboxylic acid also classified as a fatty acid. It exists in two isomeric forms as shown previously, but this entry focuses on n-butyric acid or butanoic acid. It is a colorless, viscous, rancid-smelling liquid that is present as esters in animal fats and plant oils. Butyric acid exists as a glyceride in butter, with a concentration of about 4% dairy and egg products are a primary source of butyric acid. When butter or other food products go rancid, free butyric acid is liberated by hydrolysis, producing the rancid smell. It also occurs in animal fat and plant oils. Butyric acid gets its name from the Latin butyrum, or butter. It was discovered by Adolf Lieben (1836—1914) and Antonio Rossi in 1869. 

However, for some specific reactions, solvent-free systems are preferred because of their higher yields. The main area of development should be related to the hydrolysis of glycerides, transesterification, esterification and inter-esterification reactions. As lipases have high and stable activity in SC CO2 (even at the high temperature) an intensive development is expected. 

Luhtala, A., Korhonen, H., Koskinen, E. H. and Antila, M. 1970A. Glyceride synthesis and hydrolysis caused by cells in milk. 18th Int. Dairy Congr. Proc. IE., 80. 

The phosphoric acid esters of diacyl glycerides, phospholipids, are important constituents of cellular membranes. Lecithins (phosphatidyl cholines) from egg white or soybeans are often added to foods as emulsifying agents or to modify flow characteristics and viscosity. Phospholipids have very low vapor pressures and decompose at elevated temperatures. The strategy for analysis involves preliminary isolation of the class, for example by TLC, followed by enzymatic hydrolysis, derivatization of the hydrolysis products, and then GC of the volatile derivatives. A number of phospholipases are known which are highly specific for particular positions on phospholipids. Phospholipase A2, usually isolated from snake venom, selectively hydrolyzes the 2-acyl ester linkage. The positions of attack for phospholipases A, C, and D are summarized on Figure 9.7 (24). Appropriate use of phospholipases followed by GC can thus be used to determine the composition of phospholipids. 

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. 

Rancidity, due to free volatile latty acids liberated froni the glycerides by enzymic (lipasei hydrolysis. Lipases are normal components of raw milk, and are inactivated by the heat of pasteurization. 

The dedd cells of the mycelium of Rhizopus arrhizus constitute d naturally immobilized lipdse very active in organic solvents. This immobilized enzyme was used for hydrolysis and synthesis of ester bonds triglycerides hydrolysis, and interesterification, esters and glycerides synthesis. More recently, the catalytic system has been applied in drug synthesis to the resolution of racemic esters with a good enantioselectivity. 

Rhizopus arrhizus dead mycelium was found to be very active in organic solvents as a naturally immobilized lipase. Triglycerides hydrolysis and interesterification, esters and glycerides synthesis, natural flavour esters preparation and racemic mixtures resolution in pharmaceutical drugs synthesis are among the successfully designed processes, each of one with a specific reactional medium. 

Most of the fatty acids in fats are esterified with glycerol to form glycerides. However, in some fats, particularly where abuse of the raw material has occurred leading to enzymatic activity, considerable (>5%) free fatty acid (FFA) is found. Hydrolysis occurs in the presence of moisture. This reaction is catalyzed by some enzymes, acids, bases, and heat. Most producers of fats attempt to prevent the formation of free fatty acid because certain penalties are assessed if they are present in the trading of crude and refined fats. 

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. 

Hydrolysis is the other important mechanism for some lipids (glycerides and phosphoglycerides) to degrade. Lowering of pH can arise from both hydrolysis and lipid peroxidation (Arakane et al., 1995), as both processes can give acid products. It has also been reported that hydrolysis and peroxidation can act in synergy with one another in liposome bilayers (Swern, 1995), but it is uncertain whether this can happen for other structures since different mechanisms are operative for... 

As mentioned, hydrolysis is the other important mechanism by which some lipids (glycerides and phosphoglycerides) degrade and can lead to a reduction in pH due to liberation of free fatty acids this was discussed in Chapter 10 (Part I Parenteral Application). This phenomenon is less important for oral formulations when compared to parenteral products, since the former generally have low amounts of water in the formulation. Hydrolysis could occur on storage if water is absorbed from or through the gelatin shell. 

Glowacz et al. (1996) Batch Hydrolysis of triolein and its partial glycerides Porcine pancreatic lipase... 

There are many pharmaceutical applications for the modification of one enantiomer over another, and to this end, many have studied these selective reactions in carbon dioxide. Glowacz et al. (1996) studied the enzymatic hydrolysis of triolein and its partial glycerides and found that stereoselectivity depends on reaction time and enzyme water content. They suggest that the water content varies the local environment of the enzyme in carbon dioxide and changes the local pH value. Rantakyla et al. (1996) also found that the hydrolysis of one stereoisomer over another was water-dependent. They studied the hydrolysis of 3-(4-methoxyphenyl)glycidic acid methylester and found that the 2S,3R enantiomer hydrolyzed more than fivefold faster than the 2R3S form. 

Glowacz, G. Bariszlovich, M. Linke, M. Richter, P. Fuchs, C. Morsel, J. T. Stereoselectivity of Lipases in Supercritical Carbon Dioxide. I. Dependence of the Regio- and Enantioselectivity of Porcine Pancrease Lipase on the Water Content During the Hydrolysis of Triolein and its Partial Glycerides. Chem. Phys. Lipids 1996, 79, 101-106. 

Several processes for the production of biodiesel fuel have been developed by acid-, alkali-, and enzyme-catalyzed transesterification reactions (7-10). Transesterification, called alcoholysis, is the displacement of alcohol from an ester by another alcohol in a process similar to hydrolysis. Transesterification is represented by a number of consecutive and reversible reactions. The reaction step is the conversion of triglycerides to diglycerides, followed by the conversion of diglycerides to monoglycerides and of monoglycerides to glyceride at each step (11,12). 

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