Stabilizing effect of acacia gum on the xanthan helical conformation in aqueous solution

The present study focuses on the thermal stability and helical conformation of xanthan molecules (GX) in the presence of acacia gum (GA). The viscoelastic measurements of GX–GA mixtures at different gum ratio and concentrations in a large range of temperatures, below and above GX conformational transition temperature (Tm) evidenced that the presence of GA shifts the GX Tm to higher temperature, therefore illustrating a stabilizing effect of xanthan helical conformation in the presence of GA. In addition, the impact of GA on the GX order-to-disorder transition temperature remains the same whatever the pH and ionic strength values. Furthermore, Circular dichroism measurements point out an increase of ordering of the xanthan molecule which is proportional to the logarithm of the GA concentration. We conclude that the xanthan ordering is caused by an enhancement of the screening effect of the electrostatic repulsions between its carboxylate functions due to a counter ions exchange between both gums.