Influence of Biopolymer–Biopolymer Interactions on Selected Rheological Properties of Aqueous Ionic Hydrocolloid Solutions

The influence of biopolymer-biopolymer chain interactions on selected rheological properties of aqueous solutions from konjac (KG), xanthan gum (XG), and carboxymethyl cellulose (CMC) was investigated using viscosity measurements in extensional and shear flow, as well as normal force (FN) measurements generated in shear flow. It was found that a KG solution of 0.05% behaves as a Newtonian fluid. Other solutions of KG (0.1, 0.2%), XG, and CMC revealed a non-linear dependence of viscosity on the shear rate. The extensional viscosity dependence on the elongation rate was non-linear and indicated shear-thinning over the entire KG concentration range, with the lowest values noted at 0.05% (0.5-0.8 Pas) and the highest at 0.2% (1.0-1.3 Pas). Similar observations were obtained with 0.1% XG and CMC solutions. Analysis regarding the shear rate dependence of the FN showed that hysteresis was observed for all KG concentrations tested. Only for the 0.2% KG solution were the FN values negative over the entire range of shear rates estimated, as in the case of the XG and CMC solutions. The obtained time constants from the DeKee model indicate the dominance of elastic contributions for the XG and CMC solutions and viscous contributions for the CMC solutions in the case of an extensional flow.