Xanthan improvement

Welan has similar properties to xanthan gum except that it has increased viscosity at low shear rates and improved thermal stabiUty and compatibihty with calcium at alkaline pH (90). The increased thermal stabiUty has led to its use as a drilling mud viscosifter especially for high temperature weUs. The excellent compatibihty with calcium at high pH has resulted in its use in a variety of specialized cement and concrete appHcations. 

In addition to the normal problems of completely dissolving particles of water-thickening polymers, xanthan gum contains insoluble residues which decrease polymer injectivity. Various methods of reducing insolubles content and improving xanthan solution injectivity are available (80—87). None appears economically viable. Oxygen scavengers (88) and bactericides (77,89) are commonly used to stabili2e injected polyacrylamide and xanthan gum solutions (90—102). 

Different polysaccharides change the perception of flavour, thus xanthan is superior to gum guar in the perception of sweetness. Mixtures of xanthan and locust bean gum have improved flavour release and texture when used in pies and pat s compared to starch. Many foods are emulsions, examples being soups, sauces and spreads. Exopolysaccharides are used to stabilise these emulsions and prevent the phases from... 

The higher elastic modulus (a measure of structure in solution) of rhamsan suggests that it should be superior to xanthan as a stabiliser. Rhamsan also has improved salt compatibility and is used in fertiliser suspension (high polyphosphates) and explosives (high ammonium nitrate). 

Both nonionic and anionic surfactants have been evaluated in this application (488,489) including internal olefin sulfonates (487, 490), linear alkylxylene sulfonates (490), petroleum sulfonates (491), alcohol ethoxysulfates (487,489,492). Ethoxylated alcohols have been added to some anionic surfactant formulations to improve interfacial properties (486). The use of water thickening polymers, either xanthan or polyacrylamide to reduce injected fluid mobility mobility has been proposed for both alkaline flooding (493) and surfactant enhanced alkaline flooding (492). Crosslinked polymers have been used to increase volumetric sweep efficiency of surfactant - polymer - alkaline agent formulations (493). 

Xanthan, used in EOR trials in the USA, and still being considered elsewhere, has found a niche in drilling fluids, which, together with other oilfield uses, accounts for some 2000 tons per year. Xanthan solutions have several useful properties they display a highly pseudoplastic rheology, are tolerant to salt, and have good thermal stability. There was we felt, however, some scope for improvement. 

Benichou, A., Aserin, A., Lutz, R., Garti, N. (2007). Formation and characterization of amphiphilic conjugates of whey protein isolate (WPI) / xanthan to improve surface activity. Food Hydrocolloids, 21, 379-391. 

Increasing knowledge of the biosynthesis and nutritional requirements that affect the yield and acyl composition of xanthan gum should allow production of an improved and unvarying product 96,198,277... 

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