Starch electrolyte effects

Repulsive forces between Fe oxide particles can be established by adsorption of suitable polymers such as proteins (Johnson and Matijevic, 1992), starches, non-ionic detergents and polyelectrolytes. Adsorption of such polymers stabilizes the particles at electrolyte concentrations otherwise high enough for coagulation to occur. Such stabilization is termed protective action or steric stabilization. It arises when particles approach each other closely enough for repulsive forces to develop. This repulsion has two sources. 1) The volume restriction effect where the ends of the polymer chains interpenetrate as the particles approach and lose some of their available conformations. This leads to a decrease in the free energy of the system which may be sufficient to produce a large repulsive force between particles. 2) The osmotic effect where the polymer chains from two particles overlap and produce a repulsion which prevents closer approach of the particles. 

The effects of the electrolyte concentration on gel viscosity are typically insignificant. For example, it was reported543 that a 100-fold increase of the electrolyte concentration changes the viscosity by only 3%. Such a result suggests that, again, only interactions of ions with a phosphoric acid moiety are involved. However, the effect of salts on the specific rotation of starch gels points to interactions between ions, and the amylose helix and amylo-pectin.516... 

Thermal effects of electrolyte adsorption on potato starch have also been observed.476 For the alkali-metal salts, adsorption and accompanying... 

It is well known that starch-iron complexes are suitable for fortifying bread and flour with iron. The state of iron in flour, dough, and bread was investigated by Leichter and Joslyn.643 Iron salts influence the whiteness of sweet-potato starch, but this effect is variable.644 It was also reported645 that colloidal iron interacts with starch, a process which is used to fractionate starch into three portions The first portion (80% of the total amount) is formed by colloidal iron itself, the second (9% of the total) is formed by iron and electrolytes, and the third portion (11% of the total) is not precipitated at all. 

Clearly, the smaller is the gold or rubin number, the more effective is the biopolymer at shielding the dispersion from coagulation by electrolytes. To describe this shielding phenomenon, Zsigmondy coined the term protective colloid ( Schutzkolloide ), which functions by protective action. From the results recorded in Table 2.1, it can be inferr that sodium casemate is considerably more effective in its protective action than is, say, dextrin or potato starch. Note that both of these latter polymers are nonionic in character. 

Interest in the genetic engineering of both plants and micro-organisms for the production of tailor made amylose, amylopectin and/or starches has also been reported. Furthermore, investigations on the enzymatic modification of starch and its major components, for example the introduction of additional branches composed of glucose and/or other monosaccharides and/or uronic acids as well as amino acids or peptides, to produce carbohydrates of possibly comparable functionality to galactomannans, pectin, gum arable, etc., has been initiated. Also studies on the metabolic fate of carbohydrates in food, the biosynthesis of starch, the fine structure of starch from different sources, the effect of electrolytes on the gelatinization of starch and the development of enzymic methods for starch analyses are still active. 

In the case of finer suspensions such as wheat starch or quartz powder, the particles of which have a diameter of 0.001 to 0.005 mm., the effect of electrolytes is more marked. The particles flock together to form larger aggregates, and these aggregates precipitate more rapidly than do the individual particles. The much investigated turbid solutions of clay exhibit this to a marked degree, as shown by the work of Schlosing f and Bodlander.f These solutions behave in a manner very similar to that of irreversible hydrosols such as colloidal metals, which are also very sensitive to the action of electrolytes. 

It has been reported previously that coagulation and flocculation have been employed with various degree of success in treating slimes or slurries left behind by mining activities 11,2). Both inorganic electrolyte and synthetic polymer are used Jointly to effect destabilization of these slurries. Natural products such as corn starch and hydrolysed Cassava have also been successfully empolyed in the flocculation of tar sand tailings [31. However in our search for an effective flocculant for tin tailings sluny, essentially a stable dispersion of clay minerals, we have not had much success with any of the commercial... 

Perfluorochemical oxygen earners are not soluble in water. Therefore, perfluori-nated chemicals cannot be administered in the pure form but have to be converted to an aqueous emulsion. A surfactant, selected for its effectiveness and biochemical compatibility, serves as an emulsifier. Osmolarity and oncotic pressures are adjusted by adding electrolytes and oncotic agents, such as hydroxyethyl starch. Nutrients, thrombolytic agents, therapeutic agents, and other additives may be included in the emulsion, depending on the particular clinical application of the emulsion. 

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