Evaluation and modelling of rheological properties of microwave treated xanthan gum solution

The aqueous solution of xanthan gum has high viscosity and pseudoplastic behavior. This research aimed to analyze the effect of microwave pretreatment at different time intervals (0, 1, 2, and 3 min) on the viscosity and rheological behavior of xanthan gum solution. The results showed that the apparent viscosity of xanthan gum solution (untreated solution) reduced from 0.177 Pa.s to 0.036 Pa.s with increasing shear-rate from 12.2 s-1 to 171.2 s-1. Also, the apparent viscosity of xanthan gum solution reduced from 0.070 Pa.s to 0.046 Pa.s with increasing the microwave pretreatment time from 0 to 3 min (shear-rate=61.2 s-1). The flow behavior of all samples was successfully modeled with Power law, Bingham, Herschel-Bulkley, and Casson models, and the Herschel-Bulkley model was selected as the better model to describe the flow behavior of xanthan gum solutions. The Herschel-Bulkley model had an acceptable performance with the maximum correlation coefficient (r) (higher than 0.9032) and the minimum sum of squared error (SSE) (lower than 0.7165) and root mean square error (RMSE) (lower than 0.2552). The yield stress and consistency coefficient (Herschel-Bulkley model) of xanthan gum solution increased from 0.095 Pa to 0.450 Pa, and from 0.659 Pa.sn to 0.811 Pa.sn, with increasing microwave pretreatment time from 0 to 3 min, respectively. The flow behavior index (Herschel-Bulkley model) of xanthan gum solutions decreased from 0.440 to 0.328 while the duration of microwave treatment increased.