Pasting properties of non-waxy rice starch-hydrocolloid mixtures

The swelling and pasting properties of non-waxy rice starch-hydrocolloid mixtures were investigated using commercial and laboratory-generated hydrocolloids. The swelling power of the rice starch-hydrocolloid mixtures was generally depressed at low concentration of hydrocolloids (0-0.05%), but increased directly with increasing hydrocolloid concentrations (0.05-0.1%). In gellan gum dispersion, the swelling power at 100 degrees C was higher than that of control. The rice starch-hydrocolloids mixtures showed shear-thinning flow behavior (n = 0.26-0.49). Hydrocolloids except the exopolysaccharide from S. chungbukensis (EPS-CB) increased apparent viscosity and consistency index (K) of rice starch dispersions, but decreased the n value. Hydrocolloids enhanced the trough and final viscosity of rice starch dispersions but EPS-CB reduced the viscosity of rice starch pastes. Hydrocolloids lowered peak viscosity but addition of guar gum resulted in high peak viscosity, apparent viscosity, and consistency index of rice starch dispersions. Total setback viscosity appeared to be not affected by hydrocolloids at low concentration (0.05%). The hot and cold paste of the starch-gellan gum mixture exhibited the highest viscosity values in the Brookfield viscometer.