Polysaccharides water solubility

A traditional system for the preparation of table olives, involves a treatment of the fresh fruit with a solution of NaOH to hydrolised the bitter glycoside oleuropein, followed by a lactic fermentation in brine. The modifications that take place on pectic polysaccharides of olives (Manzanilla variety) during this process was smdied. Processing induced a net loss of polysaccharides soluble in sodium carbonate and a paralel accumulation of water and Imidazole/HCl soluble polysaccharides. A general decrease of the apparent molecular weight of water and carbonate soluble polysaccharides was also detected. 

Polysaccharide solubility in aqueous solutions usually is dependent on polymer size and its allied three-dimensional structure. Even water-insoluble carbohydrates may be solubilized by controlled hydrolysis of o-glycosidic linkages to create smaller polysaccharide molecules. Thus, cellulose may be solubilized by heating in an alkaline solution until the polymers are broken up sufficiently to reduce their average molecular weight. Many such soluble forms of common polysaccharides are available commercially. 

Polysaccharides Natural Enzymatic reactions Pullulans (soluble in water), dextrans (soluble in water)... 

Some of the most important water-soluble polymers belong to the family of polysaccharides. Soluble polysaccharides were discussed in a review by Franz on polysaccharides in pharmaceutical formulations. Due to their industrial importance, key characteristics and typical applications of those polysaccharides are listed in Table 3. In addition to those noted in Table 3, the oxidation of cellulose (to convert 16-24% of its primary hydroxyl groups to carboxyl groups) produces oxidized cellulose, a fibrous white powder. It is used as a bioabsorbable hemostatic agent. The bioabsorption may be partly attributed to solubilization through the carboxylate moieties. 

Hemicelluloses high molecular mass polysaccharides of p-l,4-linked hexose and pentose residues, often also containing uronic acid. H. occur in woody parts of plants together with cellulose, serving as structural compounds and sometimes as reserve substances. They are insoluble in water, but soluble in dilute alkali. Humans and animals cannot digest them. Important H. are arabans, xylans, glucans, galactans, fructans and mannans. 

The solubility of polysaccharides and other functional properties depend on their structure. Linear polysaccharides dissolve with difficulty or they are completely insoluble. Such polymers are usually homoglycans with strong intra- and intermolecular non-bonding interactions. As a result of highly organised structures, some parts of the molecules even have crystalline structure and polar groups capable of interaction with water are not available. An example of a polysaccharide insoluble in cold water and soluble in hot water is amylose. Cellulose is insoluble even in hot water, but it is soluble in alkaline solvents. 

High stereoregularities are also confirmed from specific rotation of the polysaccharides. 3-0-Methyl [P3] and 3-deoxy [P6] homopolymers were soluble in water and dimethyl sulfoxide. 3-C-methyl-3-0-methyl [P5] and dideoxygenated polymers [P7], [P8], and [P9] were partially soluble in water and soluble in dimethyl sulfoxide. 3-0-octadecyl polysaccharide [P4] was insoluble in water and soluble in chloroform and benzene. 

Ethers can be formed with the alcohol groups of polysaccharides by reacting an alkaline solution or suspension of the polysaccharide with alkyl halides or epoxides [8]. The ethers produce polysaccharide derivatives that are usually soluble in water. This is in contrast to polysaccharide esters, which are usually insoluble in water and soluble in organic solvents. 

Mono- and di saccharides are colourless solids or sjrrupy liquids, which are freely soluble in water, practically insoluble in ether and other organic solvents, and neutral in reaction. Polysaccharides possess similar properties, but are generally insoluble in water because of their high molecular weights. Both poly- and di-saccharides are converted into monosaccharides upon hydrolysis. 

Most polysaccharides are insoluble or sparingly soluble in cold water, insoluble in cold alcohol and ether, and rarely possess melting points. Only inuUn melts at about 178° (dec.) after drying at 130°. 

Arabinan. This highly soluble polymer is found in the extracts of many fmits and seeds, in the boiling water extracts of pine wood (127), in the extracts of marshmallow roots (A/t/jaea officina/is) (128), and aspen (63) and willow (Sa/ix a/ba F) (129) bark. Because arabinan can be isolated from mildly degraded pectin fractions, it is often difficult to determine whether it is a hemiceUulose or a labile fragment of a larger polysaccharide and/or lignin complex. Arabinans have a complex stmcture composed almost entirely of 5-linked a-L-arabinofuranosyl units with similar residues linked to them at C-2 and/or C-3 and is soluble in 70% aqueous methanol solution. 

The significance of phenoxy anions is well recognized in the isolation of kraft and other water-insoluble technical lignins by acid precipitation. The ioniza tion of phenoHc hydroxyl groups coupled with the reduction of molecular size renders native lignin soluble in the aqueous pulping solution, thus enabling its separation from the polysaccharide components of wood. 

Catalytic oxidation ia the presence of metals is claimed as both nonspecific and specific for the 6-hydoxyl depending on the metals used and the conditions employed for the oxidation. Nonspecific oxidation is achieved with silver or copper and oxygen (243), and noble metals with bismuth and oxygen (244). Specific oxidation is claimed with platinum at pH 6—10 ia water ia the presence of oxygen (245). Related patents to water-soluble carboxylated derivatives of starch are Hoechst s on the oxidation of ethoxylated starch and another on the oxidation of sucrose to a tricarboxyhc acid. AH the oxidations are specific to primary hydroxyls and are with a platinum catalyst at pH near neutraUty ia the presence of oxygen (246,247). Polysaccharides as raw materials ia the detergent iadustry have been reviewed (248). 

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