Rheological Properties of Concentrated Xanthan Gum-Guar Gum Mixtures Iin Aqueous and Gum Arabic-Based Emulsion Systems

This study aimed to investigate and compare the viscoelastic synergism of xanthan gum (XG) and guar gum (GG) mixtures at different XG/GG mixing ratios (25/75, 50/50, and 75/25) in both aqueous and gum arabic-based emulsion systems. A total concentration of XG and GG was fixed at 1.0 wt.%. All mixtures exhibited pseudoplastic flow behavior. In the aqueous system, XG-GG mixtures exhibited higher consistency index (K) and apparent viscosity at 50 s⁻¹ (η_a,50) values compared to individual gums. Their relative K and η_a,50 values were higher than 1, indicating a synergistic interaction between the polymers. Conversely, in the emulsion system, the relative K and η_a,50 values were lower than 1. The XG50/GG50 mixture exhibited the lowest value, indicating no synergism. Both individual gums in the systems displayed nearly time-independent flow behavior, whereas all mixtures exhibited thixotropic behavior. Notably, a larger thixotropic area was observed in the XG50/GG50 and XG75/GG25 mixtures in the aqueous system compared to their counterparts in the emulsion system. In the aqueous system, the elastic modulus (G') of mixtures was higher than that of individual gums. The XG25/GG75 mixture exhibited higher relative G' and lower tan δ values than other mixtures. A similar trend was observed in the emulsion system, but the tan δ value of the mixtures in the aqueous system was lower than that in the emulsion system. These findings demonstrate that XG and GG exhibit different rheological synergies in aqueous and emulsion systems.