Pentosan structure

Inasmuch as the pentosan structure represents a polyacetal, the acid hydrolysis of pentosan corresponds to the hydrolysis of acetals [3]. 

Rye Proteins. While rye is the only European cereal able to completely replace wheat in bread, rye protein is not as effective as wheat protein. One reason for this is that as much as 80% of the protein in a rye sour dough is soluble compared with 10% of soluble protein in a wheat dough. One factor that inhibits the formation of a gluten-like complex is the 4-7% of pentosans present, which bind water and raise the viscosity of the dough. The crumb structure is then formed from the pentosans in combination with the starch. 

Both D-glucuronic acid and/or its 4-O-methyl ether and arabinose are also present in cereal xylans (4). Endospermic arabinoxylans of annual plants, often referred to as pentosans, are because of their branched structures more soluble in water and dilute alkali than xylans of lignocellulosic materials. They also have at least one, or even two, substituents per xylose residue (5). 

Fig. 3 Structures of acharan sulfate, dextran sulfate, suramin, pentosan polysulfate, and phosphomannopentaose sulfate (PI-88). Representative saccharide units comprising each of these polymers are shown, where n is the degree of polymerization.

M Degenhardt, P Ghosh, H Watzig. Studies on the structural variation of pentosan polysulfate sodium (NaPPS) from different sources by capillary electrophoresis. Archiv der Pharmazie 334 27-29, 2001. 

The determination of the structure of a plant gum involves the establishment of its homogeneity, its equivalent weight, and rotation and its uronic acid and pentosan content by the well-known methods. The nature of the constituent sugars and the uronic acid are then determined, after hydrolysis of the gums, by ciystallization or by conversion into characteristic crystalline derivatives. As an example the hexose mannose may be identified as the free sugar or in the form of its anilide, methyl glycoside or phenylhydrazone. Autohydrolysis of the acid... 

Contraindications Hypersensitivity to pentosan polysulfate sodium or structurally related compounds... 

In certain examples where the Smith-degradation fragments have been separated more conveniently by paper chromatography, the structure of these fragments has been demonstrated by examining their methylation products by gas-liquid chromatography. This approach has been used in studying the fine structure of lichenan,644 isolichenan,645 and wheat pentosan.848... 

A pentosanase that works on the gluten—pentosan fraction of flour results in easier dough-handling and improved cmmb structure. Pentosanases... 

The other carbohydrates in cane juice are the soluble polysaccharides vaguely classified under the terms "hemi-celluloses, soluble gums and pectins. It is possible that some of these polysaccharides may enter the juice during the milling of the cane as the plant cell structure is destroyed. A gummy product has been isolated from cane fiber by alkali extraction followed by alcohol precipitation. Acid hydrolysis of this substance yielded crystalline D-xylose and L-arabinose.10 Such gums in Trinidad cane juices were isolated by alcohol precipitation at suitable hydrogen ion concentration and assayed for pentose content by the Tollens 2-fural-dehyde assay the results showed an apparent pentosan content of 0.04-0.07%u of the Brix solids. 

Apart from their intrinsic interest the methyl ethers of certain of the pentoses, especially those of L-arabinose and D-xylose, are of great importance in structural studies of the naturally occurring pentosans, and of plant gums and mucilages.1 This also applies to the methyl ethers of L-rhamnose and L-fucose. 

The only pentosans which have been studied to any great extent are the xylans. These can be obtained from all lignified cell membranes by extraction with 5% sodium hydroxide solution after lipids, pectic materials etc. have been removed. The conditions necessary to avoid degradation during isolation have been outlined.2 Early structural determinations indicated that arabinose was present as a non-reducing end-group in a branched molecule which had a chain-length of 18-20 D-xylo-furanose residues.27 It has been shown recently, however, that the xylan from esparto holocellulose can be purified free of arabinose after several re-precipitations of the copper-complex.28... 

The existence of the mixture of polysaccharides was confirmed by Hirst and co-workers, 3 who obtained two fractions from the methylated t-galactan, one containing only a trace of pentose, whilst the other was rich in pentosan. The structure of the arabogalactan portion which was investigated was found to be highly branched. 

Interactions of aqueous electrolytes with nonionic polysaccharides play an essential role in Investigations of plant cell wall polysaccharides, where Isolation and fractionation procedures are commonly based on different degrees of solubility in particular electrolytes. This is especially true of the beta-1,4-linked pentosans and hexosans which are the primary backbone structures of most of the cell wall polysaccharides not Infrequently solubility is the basis of identification as well. The beta-1,4-linked hexosans are a special subset which, because of constraints on the freedom of rotation about the bonds of the glycosidic linkage, tend to be less soluble than the pentosans or the hexosans with less constrained linkages. 

Hemicelluloses have relatively low molar mass compared with other wood polymers. The degree of polymerization of hemicelluloses is around 80-200. The general units of hemicelluloses are pentosans and hexosans. Their general formulas are (CsHgOJn and [CgHioOsin, respectively. Hemicellulose does not have a repeated structure. There are many variations in the structure that are not well known. The detailed structure of the hemicelluloses and their abundance vary. 

Xylan, one of the better known hemicelluloses, is a component of plant cell membranes. This pentosan occurs in association with cellulose. The structure of xylan was shown to be 1,4-polyxylose ... 

The total A-starch is separated as a concentrate, while the gluten obtains its typical structure and is discharged with the B-starch via the medium fraction. The %htweight constituents of flour such as pentosane form the third phase. Following on from fine fiber screening, three-phase nozzle separators perform the task of separating the A-starch and recovering the A-starch left in the B-starch. The A-starch is washed by hydrocyclones. Two-phase decanters ensure that the two starch fractions are dewatered and process water is treated in a clarifier. 

Furan resin is a generic term for a thermoset resinous product that contains a heterocyclic unsaturated furan ring in its molecular structures. Pentosans from com cobs and rice hulls are the main sources for the key ingredient, furfural. Commercially, the furfural alcohol polymer is the most important. All furan resins are dark in color and have a reddish-black appearance when catalyzed to cure they become black. 

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