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

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 degreesC showed a high shear-thinning behavior (n = 0.23-0.28) with low magnitudes of Casson yield stresses (sigma(oc) = 4.1-20.1 Pa). The magnitudes of sigma(oc), consistency index (K) and apparent viscosity (eta(a,100)) increased with increase in concentration. The apparent viscosity over the temperature range of 25-70 degreesC 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 (eta(a)). Storage (G') and loss (G") moduli increased with increase in frequency (omega) while complex viscosity (eta*) decreased. Magnitudes of G' and G" moduli increased with increase in concentration. Cox-Merz rule was not applicable to rice flour dispersions. (C) 2004 Elsevier Ltd. All rights reserved.