Predictive model for viscosity development of modified rice starch suspension under unsteady temperature change

This study aimed to establish a predictive model that takes into account the effect of thermal history on the viscosity development of modified rice starch dispersions subject to unsteady temperature change. Experiments were conducted in a modified rheometer allowing fast heating/cooling similar to an industrial heat exchanger. The model was developed on two assumptions: (1) starch granule growth is responsible for the viscosity evolution and (2) thermal history controls the gelatinization and the granule growth of the starch dispersion. To identify the rheological parameters, modified rice starch dispersions (3%-5%) were heated from 20 degrees C to temperatures normally used in heat exchangers (105-120 degrees C) in a Couette rheometer under high heating rates (0.5-2.0 degrees C s(-1)) and shear rates (400 and 800 s(-1)). The predictive model was successfully employed to predict the viscosity of modified rice starch dispersion gelatinized under vigorous conditions