Polysaccharides volume fraction

Figure 2 Typical phase diagram of an aqueous polysaccharide (l)-protein (2) dispersion showing the Gibbs free energy as a function of the volume fraction () of each, at different temperatures from Tx, where the dispersion is metastable, to the critical solution temperature (Tc), where the two components are miscible in all proportions. ABC is the spinodal curve DBE (not connected) is the binodal curve.

In particular with respect to the fact that H2O is an integral component of the morphology and functionality of polysaccharide-containing compartments, the dependence of material characteristics on the de facto concentration or volume fraction of polysaccharides... 

In the regime exceeding c (c - (j) = 1), concentration (c) is typically replaced by volume fraction (cj)), and the polysaccharide fraction becomes equivalent... 

Finally, for volume fractions of 4> close to 1.0, polysaccharides typically form coexisting amorphous and crystalline phases, always containing several percent H2O. Hence, tj) = I is practically never observed under natural conditions, and if H2O content is reduced too much by technological processes, the system collapses and becomes insoluble forever. 

Fluid gels consist of anisometric gel particles in a continuous liquid, made, e.g., by cooling a suitable polysaccharide solution while agitating it. The modulus increases with increasing volume fraction, anisometry, and modulus of the particles. The systems generally have a yield stress. Several kinds of pastes are similar to fluid gels. 

Polysaccharides increase the viscosity of the continuous phase of the emulsion. One of the main functions of polysaccharides in emulsions is to thicken the continuous hquid. The intended effect is usually to impart a desired texture (increase viscosity or stiffness to the system and reduce buoyancy-driven creaming or sedimentation of the emulsion droplets and other particles in the system). Because of their highly swollen molecular structure in solutions, leading to a high effective volume fraction at low concentrations, most polysaccharides are very effective in providing a high viscosity at low concentration. 

Some polysaccharides, such as starch granule and inulin, are in particulate form and increase the viscosity of the emulsion by increasing the total volume fraction of dispersed material. 

Traube [80] showed that adding plant and seaweed polysaccharides led to a phase separation between an extremely dilute and a very concentrated phase. Since the particles are lighter than the solvent the concentrated phase, with volume fraction 0.5 < < 0.8, floats on top. The Iowct phase is clear and hardly contains particles. Baker [81] and Vester [82] systematically investigated the mechanism that leads to what they called (enhanced) creaming. 

Since the proteins are eluted according to the available pore volume fraction, the total separation volume cannot be larger than the total volume of the liquid in the gel phase. The relative pore volumes vary between approximately 52<7b and 97% for different SEC media, with the lower value being typical for porous glass and some silica materials and the higher for certain polysaccharide-based media. The restricted separation volume in SEC reduees the maximum number of components that can be separated to (adapted from [7]) ... 

Interactions with xanthan were investigated for some GAX fractions of wheat bran [109]. Whereas, for lowly substituted GaMs a synergy in viscosity was observed at low total polymer concentrations, yielding a maximum of the relative viscosity at nearly equal proportions of both polysaccharides [124], the xanthan/xylan mixtures at the same experimental conditions showed no synergy. The observed decrease in the relative viscosity values upon addition of the xylan indicates that a certain interaction with xanthan takes place, but that it leads to a contraction in the hydrodynamic volume. The authors suggested that structural and conformational differences between GaM and GAX might be the reason for this observation. 

Chromatorapf c methods For gel filtration of polysaccharide fraction PI, a Sephacryl S-300 chromatographyc column (1,1 X 46,7 cm) was calibrated with standard dextrans (molecular mass range 266, 72, 40, and 17 KDa Sigma Chemicals), and the void volume determined with blue dextran. Polysaccharide sample (0.5 mL 2 mg/mL) was applied and eluted with 50 mM NaOH, fractions 1 mL being collected and carbohydrate absorbance (phenol-H2S04) being monitored. 

Eor obtaining neutral fraction the column was eluted with water firstly. The acidic fractions were obtained by elution of linear NaCI gradient (0-1.4 M) in water. The carbohydrate elution profile was determined using the phenol-sulphiric acid method, finally two column volumes of a 2 M sodium chloride solution in water were eluted to obtain the most acidic polysaccharide fraction. The relevant fractions based on the carbohydrate profile were collected, dialysed and lyophilized. 

Belkin et al. 29> were first to examine various polysaccharide fractions from higher plants for their antitumor activity. They could demonstrate that many of these fractions produced haemorrhagic necrosis in different tumor types. In most cases, the polysaccharides were injected intraperitoneally into mice carrying Sarkoma 37 ascites tumor. The result was a progressive increase in cell volume and in cytoplasmic vacuolization. Osswald 30) found that tragacanth, gum arabic, and CMC reduced tumor cells in Ehrlich ascites carcinoma in female NMRE mice. The effect depended upon the dose, the route of injection, and the molecular size of the polysaccharides administered. 

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