Rheological properties of rice starch dispersions in dimethyl sulfoxide

The steady and dynamic shear rheological properties of rice starches dispersed in dimethyl sulfoxide (DMSO) solution (90% DMSO-10% water) were evaluated at various concentrations (7, 8, 9 and 10%, w/w). Rice starch dispersions in DMSO solution at 25 degrees C showed a shear-thinning flow behavior (n=0.44-0.60) and their consistency index (K) and apparent Viscosity (eta a,100) increased with the increase in concentration. The apparent viscosity over the temperature range of 25-70 degrees C obeyed the Arrhenius temperature relationship, indicating that the magnitudes of activation energy (E-a) were in the range of 11.7-12.7 kJ/mol. The Carreau model provided better fit on the shear rate-apparent viscosity data than the Cross model. Dynamic frequency sweep test showed that both storage modulus (G) and loss modulus (G") of rice starch dispersions increased with the increase in concentration. G" showed a higher dependence on frequency (omega) compared to G' due to the higher G" slopes. All rice starch dispersions showed the plateau of G' at high frequencies. Intrinsic viscosity of rice starch dispersions in DMSO was 104.1 mL/g.