Recrystallization Kinetics and Glass Transition of Rice Starch Gel System

The effect of storage temperature on recrystallization and glass transition temperature (Tg) of nonwaxy and waxy rice starch gel systems containing 60% moisture content was investigated by differential scanning calorimetry to understand the relationship between them. The nucleation and propagation for the recrystallization process were determined by recrystallization degree obtained from crystallite melting enthalpy changes during storage. The recrystallization rate for both rice starch gels within 3 days of storage and its temperature dependence were analyzed by Avrami and Arrhenius equations. The maximum nucleation and propagation for recrystallization of both rice starch gel systems occurred at 4 °C and 30 °C, respectively. The Tg slightly increased with increasing recrystallization degree, and the highest Tg was observed in the maximum recrystallization temperature ranges. The Tg and recrystallization rate of nonwaxy rice starch gel were changed more than those of the waxy one, while the higher activation energy and Q10 value were shown in waxy rice starch gel. Keywords: Recrystallization; glass transition; rice starch gel; nucleation; propagation; Avrami equation; Arrhenius equation