Rheological Properties of Deacetylated Xanthan in Aqueous Media

Abstract

Flow properties of aqueous deacetylated xanthan solutions could be approximated to pseudoplastic behavior at concentrations below 0.1% but to plastic behavior above 0.3%. The flow indices in the power law for the deacetylated xanthan were somewhat different at various concentrations. The apparent viscosity of deacetylated xanthan decreased with increasing temperature at relatively low concentrations from 0.1 to 0.5%, however, it increased with increasing temperature, showed a maximum value at 40°C and decreased gradually at 1.0%. Compared with native xanthan, deacetylated material showed higher dynamic viscoelasticity at high concentrations. The dynamic viscoelasticity of deacetylated xanthan decreased with increasing temperature at various concentrations. The dynamic viscoelasticity of deacetylated xanthan was decreased by addition of urea (4.0M).
This suggests that acetate residues, which are attached to the inner mannose residues of the side chains, contribute to the intramolecular association, and that the side chains of xanthan become more flexible after deacetylation.