Steady and dynamic shear rheology of glutinous rice flour dispersions

The steady and dynamic shear rheological properties of Korean glutinous rice flour dispersions were evaluated at different concentrations (4, 5, 6, 7 and 8%). Glutinous rice flour dispersions at 25°C showed a shear-thinning behaviour (n = 0.487-0.522) with low magnitudes of Casson yield stresses (σ_oc = 0.056-0.339 Pa). The magnitudes of σ_oc, consistency index (K) and apparent viscosity (η_a,100) increased with the increase in concentration. The power law model was found to be more suitable than the exponential model in expressing the relationship between concentration and apparent viscosity. The apparent viscosity over the temperature range of 25-70°C obeyed the Arrhenius temperature relationship, with high determination coefficients (R² = 0.982-0.998), indicating that the magnitudes of activation energies (E_a) were in the range of 9.05-11.89 kJ mol^-1. A single equation, combining the effects of temperature and concentration on η_a,100, was used to describe the flow behaviour of glutinous rice flour dispersions. Magnitudes of storage (G′) and loss (G″) moduli increased with the increase in concentration and frequency. Magnitudes of G′ were higher than those of G″ over most of the frequency range.