Relationships between phase transition and quality characteristics of cooked rice during storage

The objective of this study was to determine crystalline structures, phase transitions, textural properties, and morphological characteristics of cooked rice with different amylose contents during storage at 4 °C for 14 days. Moisture content of cooked rice decreased from 64.8% to 60.2% during storage. Relative crystallinity increased during storage, indicating an increase in ordered structure by starch recrystallization. During the storage, ice freezing and ice melting enthalpies of cooked rice decreased and glass transition temperature (T_g′) increased. Inner structure of cooked rice showed smaller holes and a thicker surrounding matrix in waxy or non-waxy rice varieties and polyhedral structure in high-amylose variety. Ice melting enthalpy of cooked rice was positively and negatively correlated with hardness and adhesiveness, respectively. T_g′ was positively correlated with adhesiveness. These results indicate that phase transitions of cooked rice with different amylose contents were significantly related to their crystalline structures, morphologies, and textures during storage.