Micro-rheological and micro-heterogeneity properties of soluble glutinous rice starch (SGRS) solutions studied by diffusing wave spectroscopy (DWS)

As a natural biopolymer, soluble glutinous rice starch (SGRS) is widely used in the food industry; and has better binding characteristics than dextrin. The micro-structural heterogeneity and micro-rheology of SGRS solutions were investigated by the novel technique diffusion wave spectroscopy (DWS). By comparing the mean-square displacement (MSD) of the microbeads imbedded in six concentrations of SGRS solutions, we found that the solutions exhibited nearly homogeneous behavior at ≤ 0.5%, but the material displayed a clear degree of heterogeneity at > 1%. Micro-rheology investigation revealed that SGRS solutions showed nearly perfect viscous behavior at ≤ 0.5%, but the property changed into viscoelastic one at > 1%. The magnitude of high-frequency viscoelastic moduli for the 3–5% SGRS solutions can be characterized by G∗\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left| {{\text{G}}^{ * } } \right|$$\end{document} ∝ ω3/4, which is the semi-flexible polymer behavior. However, the magnitude of high-frequency viscoelastic moduli (G∗\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left| {{\text{G}}^{ * } } \right|$$\end{document}) for the 7–10% SGRS solutions is proportional to ω1/2, which is the flexible polymer behavior. All micro-structural heterogeneity and micro-rheological property shifts occurred in relatively small concentration ranges.