Polysaccharides dispersibility

Chan, P.K. Chan, T.-W.D. Effect of Sample Preparation Methods on the Analysis of Dispersed Polysaccharides by MALDl-TOF-MS. Rapid Commun. Mass Spectrom. 2000,14, 1841-1847. 

Electrolytes affect dispersed polysaccharides through water inactivation, specific ion binding, and polyanion neutralization. Each effect is valence-dependent, but is less on neutral polysaccharides than on ionic polysaccharides. Di- and polyvalent cations gel or precipitate a constant amount of polysacchride at much lower concentrations than do monovalent cations. The precipitation reaction is used to advantage in isolating pectin with alkaline Al3+, because this cation and polymeric forms of Al(OH)3 readily precipitate and entrain pectinic acid from apple tissue homogenates. Other di- and polyvalent cation effects are crosslinking (Prud homme et al., 1989) and an increased rate of (3 elimination over monovalent cations (Sajjaanan-... 

Three polysaccharide-water interfaces are shown in Fig. 1. The agarose interface is observed to be indifferent to water (Hayashi and Kanzaki, 1987), judging from its distinctly sharp, hydrophobic boundary. The methylcellu-lose and pectin boundaries are diffuse and clearly hydrophilic. The air bubbles on methylcellulose attest to its efficacy as a foam stabilizer. The interfaces depicted in Fig. 1 can be visualized on a macromolecular scale as the interfaces between dispersed polysaccharide molecules and water. 

For polysaccharide dispersions, SV is exceedingly small relative to Vi. Equations (3.11) and (3.12) are mathematical propositions that the exchangeable energy stored in a dispersed polysaccharide solute is equal to the energy absorbed from an external source and any increase in surface area of the solute is consequently a repository of +A . Conversely, aggregation and desorption correspond to a loss of energy, felt as heat in the latter occurrence ( —A ) when a dry polyaccharide powder is wetted (positive adsorption). 

The solute-water interaction extends 1-3 nm (Israelachvili, 1992) and decays exponentially with distance (Van de Ven, 1989). Non-free-draining water is water within this distance traveling with the same velocity as the particle nucleus. At the interface between the non-free-draining (bound) water and the outer volume of free-draining water traveling at a different velocity, an fc [Eq. (3.27)] is generated. In this sense, hydration and the imaginary shear plane have enormous ramifications for human oral sensations elicited by dispersed polysaccharides. 

Mark-Houwink Constants for Some Dispersed Polysaccharides... 

Using the density equation of dispersed polysaccharides at concentrations obeying Raoult s law, , may be obtained from Vt vs ct (Walter and Matias, 1989). When V vs ci is not linear, < >, must be stated at a given c,. Subsequent to 4>, determinations, configurational AS [Eq. (3.22)] were calculated for low-and high-methoxyl pectin. Low-methoxyl pectins were discovered to be less inclined to order themselves in an aqueous medium than high-methoxyl pectins (Walter, 1991). 

Next, with another of his students, he turned to editing the book Industrial Gums. Now in its third edition, Industrial Gums is a praetieal book that deseribes the chemistry, properties, and applications of water-soluble or water-dispersible polysaccharides and polysaccharide derivatives with commereial value or potential. In the introductory chapter of this book, Professor Whistler presented important concepts about the relationships of structure to properties of polysaeeharides, an area he championed after it had been introduced by D. A. Rees. 

In some cases, solvents do remain in the final product One sueh example oeeurs in the preparation of liquid vanillin composition used in food and cosmetics production. The preparation of such a solution is complex. The solution must be pourable at room temperature, have high solids concentration (50-70%), be mechanically and chemically stable, be easy to dilute, be transparent, be stable to bacteria, and inexpensive. The solvents include water, ethanol, and propylene glycol. Polymeric liquid crystals are prepared by dispersing polysaccharide in water. These liquid crystals arc used for perfumes. Xanthan gum is also in use for thickening cosmetics. ... 

A. Preparation of Water-Soluble Polymer Solutions. Aqueous W-SP solutions were prepared by adding the required weight of polymer to 300cc of deionized water under vigorous agitation (Waring blendor) for approximately 20 seconds. The dispersed polysaccharide slurries were immediately added to 700cc of water and stirred by blade impellers until dissolution occurred. 

Water evaporation performed above the glass transition temperature of the polymer. During water evaporation, the solid content in the medium increases and the latex particles get closer, adopting a polyhedral form. In this way, a continuous polymeric film is created, containing the dispersed polysaccharide nanoparticles. 

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