Molecular Origin for the Thermal Stability of Waxy‐rice (Kogane) Starch

The non‐Newtonian behavior and dynamic viscoelasticity of waxyrice starch (Kogane) in aqueous solution were investigated. The flow curves, at 25°C, of starch showed plastic behavior at various concentrations. The viscosity increased a little with increase in temperature up to 5 or 10°C, then it stayed at a constant value with further increase of the temperature. The dynamic viscoelasticity showed very large values and stayed constant during increase of the temperature at various concentrations. The dynamic modulus decreased a little upon addition of urea (4.0M) and in 85% DMSO during increase in the temperature. The dynamic modulus, however, showed very low value in 0.10N NaOH solution. Intramolecular associations of waxy‐rice starch molecules might play a dominant role in the thermal stability for viscosity and dynamic viscoelasticity in aqueous solution.