Evaluation of shear yield stress and apparent viscosity of xanthan gum solutions: application of rheological models and analytical study

The use of xanthan gum (XG) in various fields is of significant interest due to its exceptional rheological properties, including viscosity, yield stress, and thixotropy. This article reports on the dependencies of steady shear stress and apparent viscosity on both shear rate and XG concentration based on experimentally obtained data using continuous shear. Three plastic models are used to analyze steady shear flow behavior and estimate yield stress. Additionally, the apparent viscosity is thoroughly discussed using the Ostwald-de Waele model. The results indicate that the aqueous XG solutions showed viscoplastic behavior. It was found that the experimental data fit better with the Herschel-Bulkley model, with high correlation coefficient (R2 > 0.909). XG concentration did not have a significant effect on apparent viscosity at high shear rates, ranging from 300 to 700 1/s. A mathematical model was developed to assess yield stress across a wide range of XG concentrations, from 0.01 to 4 wt%. Furthermore, a multiple regression model was created to evaluate the apparent viscosity as a function of XG concentration (ranging from 0.025 to 3 wt%) and shear rate.Graphic AbstractThe apparent viscosity and yield stress of xanthan gum solutions were deeply investigated.