Viscoelastic properties of konjac glucomannan in the presence of salts

Viscoelastic properties of konjac glucomannan (KGM) were studied in the entanglement region using steady and small-amplitude oscillatory rheological measurements in order to probe the role of salts on gel–sol transition temperature. It was found that gel–sol transition temperature, Theat (G′=G″\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$G^{\prime } = G^{\prime \prime }$$\end{document}), as a function of KGM concentration increased linearly with increasing salt concentration and independent of salt type. However, at higher KGM concentration, in the presence of CaCl2, the gel–sol transition temperature is higher than that of native KGM, NaCl, and KCl due to the effect of bivalent salt (Ca2+) of CaCl2 compared to the univalent salts of NaCl and KCl. The zero shear viscosity (η0) and specific viscosity are scaled as C4.0 with concentration and are also independent of the type of salt used, which confirms that KGM and salt have very minimal interaction and the viscoelastic properties are mainly due to the salting-out effect.