Rheological properties of dilute aqueous solutions of cassava starch

The effects of starch concentration on the rheological properties of dilute aqueous solutions of cassava starch were investigated. Cassava starch suspensions at different starch concentrations (0.2, 0.4, 0.6, 0.8, and 1.0 wt. %) were heated at 90 °C for 1 h and then rapidly cooled to 25 °C. The apparent viscosities of starch solutions were measured as a function of starch concentration. The cassava starch solution with a concentration of 0.2% showed Newtonian behavior, and as the concentration was increased beyond 0.4%, the solutions showed shear-thinning behavior. The flow behavior (apparent viscosity against shear rate) of the solutions was well described using a power law model. The consistency indices increased and the flow behavior indices decreased with the increasing of starch concentration. After storing the solutions at 25 °C for 24 h, precipitation of starch took place instead of gelation. The volume of precipitation bed increased linearly with starch concentration.