Effect of degree of gelatinisation on the rheology and rehydration kinetics of instant rice produced by freeze drying

The effect of degree of gelatinisation on the rheology and rehydration kinetics of instant rice produced by freeze-drying was studied. A Rapid Visco Analyser (RVA) was used to analyse the pasting properties of mixtures of ungelatinized and completely gelatinized dried rice starch at varying ratios in order to develop a standard curve between degree of gelatinization and peak viscosity. The degree of gelatinization of instant rice starch prepared by precooking (gelatinization) for varying times was determined using the calibration curve. It was found that 30 minutes or more of precooking produced completely gelatinized rice. The (RVA) pasting profiles for instant rice precooked for varying times showed that the higher the degree of gelatinization, the lower the viscosity peak, and their decrease was proportional to the degree of gelatinisation. The degree of gelatinisation increased with increase in precooking time. A study of rehydration kinetics showed than an increase in pre-gelatinization time increased the rehydration speed. The kinetics data was analysed using the Peleg's model.