Rheology of Xanthan Gum

Rheology of aqueous solutions of xanthan gum was studied over a wide range of shear rate and concentration. At sufficient dilution and low shear rates xanthan solutions show a region of Newtonian viscosity behavior. More concentrated solutions appear to show a yield stress. These results with preliminary normal stress data and effects of salt concentration are discussed in terms of the structure of this polysaccharide in solution. Intrinsic viscosity data are modeled as a suspension of rods and found to be in agreement with existing theory. We speculate the conformation of xanthan in solution is rodlike, having some flexibility. A hydrodynamic length near 1.5 μm is estimated, assuming a diameter of 19 A.