Note the structural similarity between O -acetyl- and methyl ester groups that decorate carboxylic acid residues in polygalacturonic acid. B Occurrence of O -acetyl groups in cell wall matrix polysaccharides. Adopted from Pawar et al. It has been reported that the totally acetylated xylan DA 2. Similar conclusion has also been drawn from acetylated glucomannan. One example is polysaccharides from Dendrobium officinale traditional Chinese herbs , which belong to glucomannan family but highly acetylated, as shown in Figure This polysaccharide is readily dissolved in water.
The solubility, however, is significantly decreased if the acetyl group was either removed through alkaline treatment or increased through acetylation reaction.
It has also been reported that the immunomodulating effect of this polysaccharide was also affected by the acetyl group [ 21 ]. Proposed structure of polysaccharides from Dendrobium officinale. Adopted from Xing et al. The conformation can be simply regarded as the way that polymer chains align themselves in solution to adopt an orientation with lower energies.
Two general types of conformation for polysaccharides can be simply divided—ordered conformation and disordered conformation—which is decided by the regularity of the molecular structure. In aqueous solution, most of non-starch polysaccharides with heterogeneous structure demonstrated disordered conformation, including random coil, rigid, and spherical conformation.
High-performance size exclusion chromatography HPSEC could be used to study the conformational properties of polysaccharides in aqueous solution. The double logarithmic plot of the molecular weight vs. The logarithmic plot of the molecular weight versus intrinsic viscosity of heteropolysaccharide isolated from seeds of Artemisia sphaerocephala Krasch is shown in Figure 12 , from which a random coil conformation of this polysaccharide was determined.
However, the curve in Figure 12 is not exact linear, a slightly decreased slope was observed with the increase of Mw, which was attributed to the increased percentage of side chains in the high Mw fraction by the authors [ 3 ]. Logarithmic plot of the molecular weight vs. If the values of the torsion angles are fixed by cooperative interactions between residues, such as in solid or gel states, an ordered conformation can be adopted. Two general ordered conformations are ribbon-like and helix conformations Figure Polysaccharide with ribbon-like conformation is most easily aligned and closely packed through numerous hydrogen bonds and van der waals forces.
The resultant compact structures essentially prevent solvent penetration and retain insolubility in water. Polysaccharides such as cellulose, xylan, and mannan, which contained the zig-zag type linkages, all belong to this type.
Compared to ribbon-like conformation, the hollow helix conformation showed a relative better solubility, but still not comparable with disordered conformation random coil , e. Linkage patterns and conformation types of polysaccharides: a ribbon-like and b hollow helix.
Adopted from Cui and Wang [ 23 ]. Polysaccharides with the same monosaccharides but different linkage patterns solubility also showed varied solubility. It can be seen that polysaccharides have very complex structural features regarding monosaccharide composition, glycosidic bonds linkage patterns , the degree of branching, molecular weight distribution, and the presence of special groups.
These structural features highly affected the solubility of polysaccharides, in either positive or negative way. All in all, any structure that hinders the intermolecular association usually leads to a higher solubility, such as branching structure, charged group carboxylate group, sulfate, or phosphate groups ; on the opposite, structural characters that promote the intermolecular association result in the poor solubility, such as linear chain, large molecular weight, and other regular structural characters.
It should be noted that these structural features are not isolated but intercorrelated with each other to decide the solubility of any specific polysaccharide. For example, the excellent solubility of gum arabic is not only contributed by its highly branched character but also affected by the charged group as well as the 1—6 linkage bonds.
Therefore, it is wise to consider the relationships of solubility with overall polysaccharide structure features. Some examples of polysaccharides with different solubility groups have been previously summarized [ 7 ], while some modification has been made Table 1. Understanding the relationships between solubility and structural features of polysaccharides could better facilitate the food and nonfood applications.
The solubility of some originally insoluble or poor soluble polysaccharides such as cellulose and starch can be increased through basic structural modification. Take starch for example; starch can be physically or chemically modified to improve water solubility. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.
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Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Abstract Understanding the solubility of polysaccharides is extremely important for their food applications as most functions of polysaccharides including stability, emulsifying property, drug delivery, membrane forming properties, etc. Keywords polysaccharides structure solubility conformation solution behavior. Towards efficient binders for silicon based lithium-ion battery anodes.
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RSC Advances , 6 28 , Research on Chemical Intermediates , 41 10 , Nkosi , R. Meeske , T. Langa , M. If held in excess of water, some limited swelling will occur in a small fraction but pure starch is not soluble.
Starch becomes soluble in water when heated. Granular cold-water-soluble GCWS starches were prepared by alcoholic-alkaline treatments. The method was carried out by treating starches with mixtures of ethanol and alkali, primarily NaOH solution 3M , to swell starch granules. The study showed that atrazine was physically embedded in starch matrices. Starch is a soft, white, tasteless powder that is insoluble in cold water, alcohol, or other solvents.
The simplest form of starch is the linear polymer amylose; amylopectin is the branched form. Starch granules are insoluble in cold water but disrupt if heated to form a gelatinous solution.
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