Polysaccharide-water interactions

Hydrocolloidal water is an integral part of the dispersed phase and travels at the same velocity with it this is considered tightly bound water. Yakubu et al. (1990) identified three other forms of water in potato and com starch, viz., weakly bound, surface trapped, and bulk water. All forms were not present in potato starch containing less than 35% moisture, but were present in corn starch. Water, far removed from the solute surface (unbound or free water in the outer volume), travels at a different rate from hydrocolloidal water (Lechert et al., 1981). 

Most polysaccharides affect the mobility and structuring of water (Blanshard, 1970) beyond the immediate interface (Barfod, 1988) to a thickness of several molecular diameters (Rickayzen, 1989). The reciprocal effect on flowing polysaccharides of surface-water immobilization and structuring is a contribution to distortions from sphericity, and hence to flow birefringence. 

Where there is no solute-solute association, macromolecules may act simply as a viscosity enhancer of the continuous phase Barnes et al. (1989) call this phenomenon neutral interaction. Through what is called hydrodynamic interaction (Dautzenberg et al., 1994), the streamlines of hydrocolloidal particles flowing past each other affect each other. Tightly bound water apparently does not contribute much to aw (Yakubu et al., 1990). Free water is removable from a sol by freezing, while simultaneously, soluble trace components concentrate in the hydrocolloidally bound, unfrozen water, often to saturation. 

In a binary dispersion, there is usually one of five interfaces to consider, where a polysaccharide, for example, may act as a protective colloid. These interfaces are liquid-solid (sol), liquid-liquid (emulsion), solid-solid (mixed xerogel), liquid-air (foam), and solid-air (powder). In any of these systems at 

Handbook of Chemistry and Physics, 62nd ed., CRC Press, Boca Raton, FL, 1981-1982. 

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Four features of a polymer solute figure prominently in the polysaccharide-water interactions, viz., bonding, branching, ionization, and nonuniformity of the repeating structure (Glass, 1986). 

The effect of heat on the polysaccharide-water interaction in several dispersions and suspensions was studied by comparative viscometry and rheometry (Tables I-IV). The polysaccharides were the purest manufacturers grade laboratory washed and dried before dispersion. The dispersion concentrations were below c to accommodate capillary viscometry, and the suspension concentrations were above c to accommodate rheometry. It is seen in Tables I and II that the cellulose derivatives made the most stable dispersions and the propylene glycol alginate made the least. Dispersions of the neutral polysaccharides were more stable than those of the ionic polysaccharides. From Tables III and IV, it can be argued that suspensions benefit... 

Polysaccharide-Water Interactions. These polymers exhibit a range of hydrophilicity comparable to that of proteins and interact with water in many ways similar to those already noted for... 

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. 

Polysaccharides and water interaction are especially studied for their use in spray-dried products in food and in biotechnology. ... 

Excluded volume effects may increase the effective concentration of K-carrageenan and the reduction of available water for each macromolecule may lead to increased inter- and intra-helix interactions in the polysaccharide. In the presence of other proteins (i.e. milk proteins) K-carrageenan gel formation involved mainly carrageenan - carrageenan cross-linkages and not polysaccharide - protein interactions.5,9... 

Tsvetkov, V.G., Kaimin , I F., loelovich, M.Ya., and Rabinovich, I.B., Enthalpy of water interaction with cellulose of different degree of crystallinity, All-Russia Seminar Crystallization of polysaccharides and their interaction with water Proceedings, Riga Zinatne Publ., 1979, pp. 6-8 (in Latvian). 

It was also recognized that polysaccharides can interact at the interface with other polymers (nonproteins and other polysaccharides) as well as with groups residing at the protein/water, oil/water, or air/water interface, forming an aqueous structured material with useful viscoelastic mechanical properties under... 

Starches. Starch (qv) granules must be cooked before they wiU release their water-soluble molecules. It is common to speak of solutions of polysaccharides, but in general, they do not form tme solutions because of their molecular sizes and intermolecular interactions rather they form molecular dispersions. The general rheological properties of polysaccharides like the starch polysaccharides are described below under the discussion of polysaccharides as water-soluble gums. Starch use permeates the entire economy because it (com starch in particular) is abundantly available and inexpensive. Another key factor to its widespread use is the fact that it occurs in the form of granules. 

Lipoteichoic acids (from gram-positive bacteria) [56411-57-5J. Extracted by hot phenol/water from disrupted cells. Nucleic acids that were also extracted were removed by treatment with nucleases. Nucleic resistant acids, proteins, polysaccharides and teichoic acids were separated from lipoteichoic acids by anion-exchange chromatography on DEAE-Sephacel or by hydrophobic interaction on octyl-Sepharose [Fischer et al. Ear J Biochem 133 523 1983]. 

Two helices are packed antiparallel in the orthorhombic unit cell. Association of the helices occurs through a series of periodic carboxylate potassium water - carboxylate interactions. An axial projection of the unit-cell contents (Fig. 23b) shows that the helices and guest molecules are closely packed. This is the first crystal structure of a polysaccharide in which all the guest molecules in the unit cell, consistent with the measured fiber density, have been experimentally located from difference electron-density maps. The final / -value is 0.26 for 54 reflections, of which 43 are observed, and it is based on normal scattering factors.15... 

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