Viscosity of guar gum and xanthan/guar gum mixture solutions

The viscosity of diluted guar gum solutions and the viscosity of xanthan an d guar gum mixture solutions have been studied. Guar gum solutions showed p seudoplastic behaviour. Apparent viscosity increased with gum concentration and decreased with the temperature at which viscosity was measured. A maxi mum in the plot of viscosity versus increasing dissolution temperature was observed at 60 degrees C. This behaviour was related to differences in mole cular structure of the polymers solved at different temperatures. Mixtures of xanthan and guar gum showed a higher combined viscosity than that occurr ing in each separate gum. This synergistic interaction was affected by the gum ratio in the mixture and dissolution temperature of both gums. The effe ct of polysaccharide concentration (1.0, 1.5 and 2.0 kg m(-3)), xanthan/gua r gum ratio (1/5, 4/2, 3/3, 4/2 and 5/1) and dissolution temperature (25, 4 0, 60 and 80 degrees C for both gums) on the viscosity of solutions of mixt ures were studied. The highest viscosities were observed when 2.0 kg m(-3) gum concentration was used together with a ratio of xanthan/guar gum of 3/3 (w/w) and dissolution temperature of 40 and 80 degrees C for xanthan and g uar gum, respectively. (C) 2000 Society of Chemical Industry.