Xanthan polymer, gelation

Cheetham, N. W. H. and Mashimba, E. N. M. Comfomiational aspects of xanthan-galactomannan gelation-Fuither evidence from optical-rotation studies. Carbohydr. Polym., 14,17-21 (1990). 

Nolle, H., John, S., Smidsrod, O., and Stokke, B. T. 1992. Gelation of xanthan with trivalent metal ions. Carbohydr. Polym. 18 243-251. 

The viscosities of solutions of xanthan, unlike those of all other water-soluble polymers, do not decrease as the temperature is raised. They are unaffected by temperature between 0 °C and 100 °C. And even though it is an anionic polymer, its solution viscosity is not affected by pH or most salts, i. e., although ionic, it behaves as if it were a neutral gum. Xanthan interacts synergistically with guar gum and locust bean gum (both galactomannans) (O Sect. 4.2). An increase in solution viscosity results from its interaction with guar gum. Heat-reversible gelation results from its interaction with locust bean gum. 

Zhan D. F., Ridout M. J., Brownsey G. J., Morris V. J. 1993. Xanthan-locust bean gum interactions and gelation. Carbohvdr. Polymers. 21, 53-58. 

M. lijima, M. Shinozaki, T. Hatakeyama, M. Takahashi, H. Hatakeyama, AFM studies on gelation mechanism of xanthan gum hydrogels, Carbohydr. Polym., 68,701-707,2007. 

The behavior is attributed to the filtration of gel particles that formed during the gelation reaction. Adsorption of polymer and reaction between adsorbed polymer andCr(II])/polymer in the flowing stream also contributed to the development of the resistance. The location of the point of buildup of resistance has been shown to be a fimetion of flow rate and shear in the porous medium. Similar behavior was observed for xanthan/Cr(III) gels. dlS... 

Galactomannans, xanthan and chitosans are thickening linear polysaccharides the first one is neutral, xanthan is an anionic polysaccharide and chitosan is a cationic polymer in acidic conditions. The main physical properties of these different polysaccharides in dependence with the experimental conditions (temperature, ionic concentrations, nature of counterions...) are described. Considering alginates and gellan, a specific behaviour is observed physical gelation for which the mechanisms of gelation are discussed in relation with thermodynamic conditions. 

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