Polysaccharide thickeners

Synthetic products, e.g., polyethylene oxides(104), polyacrylates, polyacrylamides, and polyetherglycols were in competition with natural polymers like starch, guar, cellulose derivatives, alignates, carrageenan, and locust bean gum. The basic physical and structural properties of the various polysaccharide thickeners have been compiled and reviewed by numerous authors and editors(105-109). 

U.S. 5336430 (1994)[123] Bahary et al. (Lever Bros.) Polysaccharide thickener encapsulated bleach and chlorine scavenger Biodegradable structurant... 

Mono- and disaccharides, alduronic acids, methylated sugars, polysaccharides (thickening agents) Silanized glass fiber paper 0.05 mol Sodium tetraborate, pH 9.0, 0.1 moll barium acetate, 0.1 moir zinc acetate, 0.1 moll calcium acetate 1,3-Dihydroxynaphthalene (naphthoresorcinol)-H2S04... 

The above chemicals can be obtained by fermentation (qv) of other sugars. However, some compounds require sucrose as a unique feedstock. Examples are the polysaccharides dextran, alteman, andlevan, which are produced by specific strains of bacteria (48,54—56). Dextrans are used to make chromatographic separation media, and sulfated dextran derivatives are used as plasma extenders (41). Levans show promise as sweetness potentiators and, along with alteman, have potential as food thickeners and bulking agents in reduced-caloric foods (55,56) (see Carbohydrates). 

CS derivatives/salts have found limited use as detergents (25), antistatic coatings for photographic film (26), oil drilling fluids (25), thickeners in food, cosmetics, and pharmaceuticals (27). They have been recommended for use as cation exchangers (28,29). Also, sulfated polysaccharides have recendy shown interesting antiviral activity (30). 

Many microbial polysaccharides show pseudoplastic flow, also known as shear thinning. When solutions of these polysaccharides are sheared, the molecules align in the shear field and the effective viscosity is reduced. This reduction of viscosity is not a consequence of degradation (unless the shear rate exceeds 105 s 1) since the viscosity recovers immediately when die shear rate is decreased. This combination of viscous and elastic behaviour, known as viscoelasticity, distinguishes microbial viscosifiers from solutions of other thickeners. Examples of microbial viscosifiers are ... 

Changes in wall architecture occur during isodiametric cell expansion, cell elongation, and the thickening of a growing wall to its mature thickness, and so it is important to define whether the synthesis and secretion of particular cell-wall molecules correlates with differentiation events or with general cell expansion. Ceils are stimulated into producing wall polysaccharides upon subculture, so we used a non-inductive medium, in which the cells only expand, for comparison with inductive medium at all times. 

Some by-products from the food industry contain high proportions of plant cell walls which can be used in human nutrition to produce "dietary fibre" or "functional fibre", i.e. compounds which can be used for their water-holding/binding properties, oil-binding capacity,... or as a source of polysaccharides such as pectins which are suitable after extraction, as gelling or thickening agents. 

Naturally occurring polysaccharides and their derivatives form the predominant group of water-soluble species generally used as thickeners to impart viscosity to treating fluids [1092]. Other synthetic polymers and biopolymers have found ancillary applications. Polymers increase the viscosity of the fi ac-turing fluid in comparatively small amounts. The increase in fluid viscosity of hydraulic fracturing fluids serves for improved proppant placement and fluid loss control. Table 17 summarizes polymers suitable for fracturing fluids. 

Natural thickeners are derived from plants by extraction from part of the plant itself or from a plant secretion their biosynthesis is now a possibility. These products are generally polysaccharides and are thus closely related to cellulose. They consist of homo- or... 

Other natural polysaccharides used as thickening agents include gum arabic, gum tragacanth and xanthan gum, but these are of diminishing significance nowadays. 

The main function of the foam stabilising agent is to reinforce the intercellular film wall by contributing rheological characteristics of viscoelasticity. The increased viscosity may also assist handling. The aim, as so often with auxiliaries, is to achieve an optimum balance. If the bubbles are too thin and wet too quickly they will collapse prematurely, whilst too stable a film could hinder uniform application. Examples of products used as foam stabilisers include thickening agents such as the polysaccharides, hydroxyethylcellulose, methylcellulose,... 

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