Non-Newtonian Flow and Dynamic Viscoelasticity of Xanthan Gum

Abstract

Non-Newtonian flow and dynamic viscoelasticity of xanthan gum (D-glucose : D-man-nose : D-glucuronic acid; acetate : pyruvic acid=3. 8 : 3. 7 : 2. 0 : 1. 7 : 0. 51~0. 63) produced commercially by Xanthomonas campestris NRRL B-1459 were investigated. The flow curves of xanthan gum were approximated to plastic flow. The flow behavior indices of xanthan gum were constant at each before and after refraction points at various concentrations. The viscosity of xanthan gum decreased lineally with the increase in shear rate and the slope did not change with concentration. The plot of logarithm of viscosity of xanthan gum against the reciprocal of absolute temperature showed sigmoid curve which disappeared by addition of salts. Dependence of dynamic viscoelasticity of xanthan gum on frequency did not vary with concentration. Dynamic viscoelasticity of xanthan gum was constant with the increase in temperature at lower concentration and showed sigmoid curves at higher concentrations. It seemed that molecular chains of xanthan gum associated in aqueous solution and dissociated by addition of salts. It was assumed that side chains of xanthan gum mainly participated in association of molecular chains of it. © 1977, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.