Rheological behavior of cooked rice flour dispersions in steady and dynamic shear

Abstract

The steady and dynamic rheological properties of Korean rice flour dispersions were evaluated at different concentrations (4%, 5%, 6%, 7%, and 8%). Rice flour dispersions at 25 °C showed a high shear-thinning behavior ( n=0.23–0.28) with low magnitudes of Casson yield stresses ( σ oc=4.1–20.1 Pa). The magnitudes of σ oc, consistency index ( K) and apparent viscosity ( η a,100) increased with increase in concentration. The apparent viscosity over the temperature range of 25–70 °C obeyed the Arrhenius temperature relationship, indicating that the magnitudes of activation energies ( E a) were in the range of 0.21–0.27 KJ/mol. The power law model was found to be more suitable than the exponential model in expressing the relationship between concentration and apparent viscosity ( η a). Storage ( G ′) and loss ( G ″) moduli increased with increase in frequency ( ω) while complex viscosity ( η ∗ ) decreased. Magnitudes of G ′ and G ″ moduli increased with increase in concentration. Cox–Merz rule was not applicable to rice flour dispersions.