Steady and Dynamic Shear Rheology of Rice Starch‐Galactomannan Mixtures

TLDR: Rheological properties of rice starch-galactomannan mixtures at different concentrations of guar gum and locust bean gum (LBG) were investigated in steady and dynamic shear as mentioned in this paper.

Abstract: Rheological properties of rice starch-galactomannan mixtures (5%, w/w) at different concentrations (0, 0.2, 0.4, 0.6 and 0.8%, w/w) of guar gum and locust bean gum (LBG) were investigated in steady and dynamic shear. Rice starch-galactomannan mixtures showed high shear-thinning flow behaviors with high Casson yield stress. Consistency index (K), apparent viscosity (q a,100 ) and yield stress (σ OC ) increased with the increase in gum concentration. Over the temperature range of 20-65°C, the effect of temperature on apparent viscosity (η a,100 ) was described by the Arrhenius equation. The activation energy values (E a = 4.82-9.48 kJ/mol) of rice starch-galactomannan mixtures (0.2-0.8% gum concentration) were much lower than that (E a = 12.8 kJ/mol) of rice starch dispersion with no added gum. E a values of rice starch-LBG mixtures were lower in comparison to rice starch-guar gum mixtures. Storage (G') and loss (G) moduli of rice starch-galactomannan mixtures increased with the increase in frequency (ω), while complex viscosity (η*) decreased. The magnitudes of G' and G increased with the increase in gum concentration. Dynamic rheological data of In (G', G) versus In frequency (ω) of rice starch-galactomannan mixtures have positive slopes with G' greater than G over most of the frequency range, indicating that their dynamic rheological behavior seems to be a weak gel-like behavior.