Glycerol oxidation process

A large number of products can be obtained from glycerol oxidation processes (Scheme 3.7). If the secondary hydroxy group of glycerol is oxidized selectively, dihydroxyacetone (DHA) is formed. DHA has been used for years as an active... 

Commercial kits are based on the Upase-catalyzed total hydrolysis of the triglyceride, followed by glycerol kinase-catalyzed synthesis of 1-glyceryl phosphate (67) and GPO-catalyzed oxidation of the latter, as shown in equation 17. The end analysis is by a chromogenic oxidation process catalyzed by peroxidase, similar to equation 27, involving 4-aminoantipyrine (81) and 3,5-dichloro-2-hydroxybenzenesulfonate (88) or iV-ethyl-iV-(3-sulfopropyl)-m-anisidine (94)28. 290... 

Oxidative stability of edible oils depends primarily on their fatty acid composition and, to a lesser extent, in the stereospecific distribution of fatty acids in the triacyl-glycerol molecules. The presence of minor components in the oils also affects their oxidative stability. A detailed discussion of oxidative processes in fats and oils is provided elsewhere in this series. Oxidation may occur via different routes and includes autoxidation, photo-oxidation, thermal oxidation, and hydrolytic processes, all of which lead to production of undesirable flavor and products harmful to health. Flavor and odor defects may be detected by sensory analysis or by chemical and instrumental methods. However, chemical and instrumental procedures are often employed in the processing and during usage of edible oils. Indicators of oxidation are those that measure the primary or secondary products of oxidation as well as those from hydrolytic processes or from thermal oxidation, including polymers and polar components (15). 

It is to be noted that in vapor phase processes such as those described by James the acids produced are aldehydic in nature and may depend upon this aldehydic character for utilization in the form of condensed products such as low grade resins, etc. Attempts to recover these acids in the form of sodium soaps usually leads to the formation of resins due to the resinify-ing action of the caustic. On the other hand, the numerous claims for the liquid phase oxidation process usually mention the formation of simple carboxylic acids or hydroxy-carboxylic acids which may be used to form edible fats by esterification with glycerol. This seems to indicate the somewhat milder oxidation possible in the liquid phase process. 

While we have not completed any bulk electro-synthetic reactions to ascertain what comprises the products of the oxidative process, we have arrived at some conclusions regarding the requisite structural features for electroactivity. Although the carbohydrates will exist in their open form under the basic conditions of the analysis, we could eliminate the requirement of a carbonyl function due to the activity of some of the alcohols such as glycerol and inositol. The requirement for a polyhydroxy functionality is evident form the inactivity of methanol and the 1,2-dihydroxy pentanes, hexanes and cis- and trans-cyclohexanes. The exception here would appear to be 2-deoxyribose, which is inactive, albite a polyhydroxy compound. Indeed, it would appear that regardless of what oxidative process is occuring, there is a requirement for three hydroxy groups in a 1,2,3-trihydroxy configuration. This is consistent... 

Considerable literature has been published on the determination of glycerol oxidation methods are the most satisfactory but obviously they depend upon its separation in a fair state of purity. Any process which involves evaporation of aqueous or alcoholic solutions to low bulk gives rise to inaccuracies as concentration is difficult and glycerol is sensibly volatile at 100, the amount of loss varying with the conditions and the apparatus used. The volatilisation may be prevented by the presence of an excess of lime with which glycerol forms a compound. 

The main route for glycerol conversion is based on the oxidation and dehydration/rehydration steps. Usually, the oxidation process is performed by a dehydrogenation or an oxidation step with oxidants. On the other hand, a dehydration reaction occurred xmder acidic conditions however, most of the reported reactions are in alkaline media. 

The nature of the diet sets the basic pattern of metabohsm. There is a need to process the products of digestion of dietary carbohydrate, lipid, and protein. These are mainly glucose, fatty acids and glycerol, and amino acids, respectively. In ruminants (and to a lesser extent in other herbivores), dietary cellulose is fermented by symbiotic microorganisms to short-chain fatty acids (acetic, propionic, butyric), and metabohsm in these animals is adapted to use these fatty acids as major substrates. All the products of digestion are metabohzed to a common product, acetyl-CoA, which is then oxidized by the citric acid cycle (Figure 15-1). 

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