ABSTRACT: An oscillating capillary rheometer was used to investigate the effects of xanthan deacetylation on the viscoelastic properties and intrinsic viscosity of xanthan and guar mixtures in dilute aqueous solutions. Deacetylated xanthan exhibited a stronger synergistic interaction with guar than native xanthan did due to the destabilized helical structure and increased chain flexibility of the deacetylated xanthan. No gels were observed for all xanthan–guar mixtures. Native xanthan–guar mixtures exhibited a liquid-like behavior, whereas deacetylated xanthan–guar mixtures exhibited a gel-like behavior. The relative viscosity and elasticity of deacetylated xanthan–guar mixtures were much stronger than those for native xanthan–guar mixtures. The intrinsic viscosities of deacetylated xanthan–guar mixtures were higher than the calculated values assuming no interaction, whereas the intrinsic viscosities of native xanthan–guar mixtures were lower than the calculated values assuming no interaction, demonstrating that intermolecular binding occurred between the disordered segments of xanthan and guar gum in dilute aqueous solutions.