Dispersibility of xanthan gum

In orifice blending, the viscosity increases as the solution passes through the orifice as shown on Figure 2. The viscosity loss upon filtration is small in this case, indicating that this high shear field device is required for the dispersion of xanthan gum. 

Borate also forms complexes with xanthan gum under alkaline conditions and cillows the design of a system for increasing the dispersibility of xanthan gum in alkaline waters. More details on this process are presented later. 

The dispersibility of xanthan gum can be improved most readily by treatment with glyoxal or alkaline borate. 

Kennedya JRM, Kent KE, Brown JR. Rheology of dispersions of xanthan gum, locust bean gum and mixed biopolymer gel with silicon dioxide nanoparticles. Mater Sci Eng C. 2015 48 347-53. 

For high-methoxylpectin dispersions, magnitudes of r) a ) were almost always lower than those of r]a(y), only converging at higher values of frequency and shear rate (Figure 4-10). Such behavior is not very common in biopolymeric systems and was reported for semidilute solutions of xanthan gum in 0.5% NaCl (Rochefort and Middleman, 1987) and aqueous solutions of hydroxyethyl guar gum... 

Figure 4-42 Values of Yield Stress of Starch-Xanthan Dispersions Relative to those of the Starch-Water Dispersions (YSA SO) and Relative Mean Granule Diameters (D/DO) Plotted against Values of c[j) of Xanthan Gum waxy maize (WXM), cross-linked waxy maize (CWM), and cold water swelling (CWS).

Achayuthakan et al. (2006) studied vane yield stress of Xanthan gum-stareh dispersions. The intrinsic viscosity of Xanthan gum was determined to be 112.3 dl/g in distilled water at 25°C. In addition, the size of the granules in the dispersions of the studied starches waxy maize (WXM), cross-linked waxy maize (CWM), and cold water swelling (CWS) were determined. The values of yield stress of the starch-xanthan dispersions relative to those of the starch-water dispersions (YSA"S0) and relative mean granule diameters (D/DO) plotted against values of c[ ] of xanthan gum are shown in Figure 4-42. With the values of YS/YSO being less than 1.0, there was no synergism between CLWM starch and xanthan gum. 

The number of passes required through an orifice to form a well-dispersed solution depends on the polymer concentration. The reservoir characteristics are needed for the final design of the orifice mixing system. Details of mixing of xanthan gum solutions were presented in an earlier study (7). ... 

Other chemical derivatives of xanthan gum would be expected to have altered dispersibility and hydration behavior. 

Add immediately after dispersing the xanthan gum it must allow proper hydration of the milk proteins to which an agitation of at least 15 min is recommended. 

Even smaller, nanometer size particles, can be prepared Irom cyclodextrin. These particles are useful as a carrier for pharmaceuticals and cosmetics. First, a solution of cyclodextrin in an organic solvent mixture is prepared, followed by the preparation of a water dispersion of surfactant. When the two components are mixed together a colloidal dispersion of microspheres is produced. Particles sizes range Irom 90 to 900 nm. Typical solvents are methanol, ethanol, isopropanol, and acetone. Solvents are used in the purification of xanthan gum to lower ash and to obtain a product with no traces of solvents. Lower alcohol is used as the solvent. Solvents have also been used to decolor fatty acid esters. Crude oils extracted by pressing or with solvents cannot be used in cosmetic products. Re-... 

The viscosity of xanthan gum dispersions is not very sensitive to ionic strength and pH (pH 3-12). Xanthan gum is incompatible with cationic surfactants because it is an anionic polymer. It is used as a thickener in toothpastes [15], shampoos, liquid soaps, food applications, creams, and lotions. Examples of the use of xanthan gum as a thickener in dentifrice formulations are the patent applications WO 9725019 A1 [41] and JP 08295637 A2 [42]. Xanthan gum is available from suppliers such as Calgon, Rhone-Poulenc, and TIC Gum under the trade names Keltrol, Rhodicare, and Ticaxan, respectively. 

Low molecular weight (1000—5000) polyacrylates and copolymers of acryflc acid and AMPS are used as dispersants for weighted water-base muds (64). These materials, 40—50% of which is the active polymer, are usually provided in a Hquid form. They are particularly useful where high temperatures are encountered or in muds, which derive most of their viscosity from fine drill soHds, and polymers such as xanthan gum and polyacrylamide. Another high temperature polymer, a sulfonated styrene maleic—anhydride copolymer, is provided in powdered form (65,66). AH of these materials are used in relatively low (ca 0.2—0.7 kg/m (0.5—2 lb /bbl)) concentrations in the mud. 

For products intended to remain stable dispersions for an extended period, a particle size of 2 p.m or less is desirable. A thickening agent is usuaUy added after the reaction has been completed and the mixture is cooled in order to prevent settling and agglomeration. Examples of thickeners are guar gum, xanthan gum, and hydroxyethylceUulose. The final products are generaUy between 40 and 50% soUds, with a viscosity of 1500 5000 mPa-s(=cP). 

For suspensions primarily stabilized by a polymeric material, it is important to carefully consider the optimal pH value of the product since certain polymer properties, especially the rheological behavior, can strongly depend on the pH of the system. For example, the viscosity of hydrophilic colloids, such as xanthan gums and colloidal microcrystalline cellulose, is known to be somewhat pH- dependent. Most disperse systems are stable over a pH range of 4-10 but may flocculate under extreme pH conditions. Therefore, each dispersion should be examined for pH stability over an adequate storage period. Any... 

Add, in small quantities, the remaining half of magaldrate cake or powder and disperse well. Mix for 1 hour and then remove heat. (Adjust the speed of the agitator and of the homogenizer to maintain the mobility of suspension.) Separately blend silicon dioxide colloidal with xanthan gum and disperse the blend in glycerin, with constant mixing. 

When a liquid dispersion contains non-adsorbing polymers there will be a layer of liquid surrounding each dispersed species that is depleted in polymer, compared with the concentration in bulk, solution. This causes an increase in osmotic pressure in the system compared with what it would be were the dispersed species absent. If the dispersed species move dose to each other then the volume of solvent depleted is reduced, reducing the overall osmotic pressure, which provides a driving force for flocculation. Xanthan gum, added in low concentrations, can cause depletion flocculation [291]. 

Xanthan gum was shown to be stiffer than CMC and alginate all three are ionic polysaccharides, with CMC having slightly more flexibility than alginate under identical conditions (R. C. Clark, 1992). The invariant nature of xanthan dispersion properties is attributed to the stability of the tertiary structure. The indifference of this gum to salt is explained by its already rigid conformation (Morris, 1976). 

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