Evaluation of retrogradation in microwave cooked rice using X-ray diffraction method.

Abstract

Progress of retrogradation of rice grain which was cooked by microwave heating was evaluated using X-ray diffraction (XRD) method. Cooked rice grains were not powdered but made to paste and measured directly, A lot of samples were able to be measured by this convenient method. The polarization microscopy was also conducted for visualization of retrogradation. The differences in retrogradation observed by XRD were found between rice grains in the cooking container like differences in cooking properties such as moisture content and degree of gelatinization. Progress of retrogradation was observed after 12 hours from beginning of storage at 5°C. Using Avrami equation, kinetic parameters of retrogradation were calculated. Rate constant of retrogradation was greatly affected by moisture content of cooked rice grain. In the case of low moisture content gave a high rate constant for retrogradation.