Rheology of rice starch-sucrose composites

The effect of sucrose at different concentrations (0, 10, 20 and 30%) on Rheological properties of rice starch pastes (5% w/w) was investigated in steady and dynamic shear. The steady shear properties of rice starch-sucrose composites were determined from rheological parameters for power law and Casson flow models. At 25°C all the starch-sucrose composites exhibited a shear-thinning flow behavior (n=0.25-0.44). The presence of sucrose resulted In the decrease in consistency index (K), apparent viscosity (η _a,100) and yield stress (σ_oc). Dynamic frequency sweeps at 25°C indicated that starch-sucrose composites exhibited weak gel-like behavior with storage moduli (G′) higher than loss moduli (G″). G′ and G″ values decreased with the increase in sucrose concentration. The dynamic (η*) and steady-shear (η_a) viscosities at various sucrose concentrations did not follow the Cox-Merz superposition rule. G′ values as a function of aging time (10 h) at 4°C showed a pseudoplateau region at long aging times. In general, the values of G′ and G″ in rice starch-sucrose composites were reduced in the presence of sucrose and depended on sucrose concentration.