Effects of particle properties, intermolecular forces, and molecular structure on the shear-thickening behavior of waxy starch dispersions

The shear-thickening phenomenon in waxy starch dispersions has been reported; however, the influence of starch properties on it remains unclear. Herein, the shear-thickening behavior of five waxy starch dispersions at different concentrations is investigated, and two shear-thickening areas are identified for the first time. Waxy potato and cassava starch dispersions present two shear-thickening areas, waxy maize and wheat starch dispersions exhibit one shear-thickening area, and waxy rice starch dispersion exhibits no shear-thickening behavior. Starches with high degree of polymerization (DP > 12 and > 37 chains), short-range order, relative crystallinity, melting enthalpy (ΔH), and low molecular weight easily form large particle fragments and strong intermolecular forces, thereby resulting in double shear-thickening areas. Starches with relatively high DP > 12 chains, short-range order, relative crystallinity, and ΔH form one shear-thickening area. Starches with no shear-thickening area have high molecular weight, degree of branching, and DP < 12 chains, and low short-range order, relative crystallinity, and ΔH. It can be speculated that the first shear-thickening area (2–5 s−1) is due to the presence of large particle fragments, whereas the second (10–15 s−1) is due to the interaction between the side chains of the starch molecule.