Effects of D-psicose on gelatinization and retrogradation of rice flour

The rare sugar D-psicose was shown to have an ability to promote gelatinization of rice flour and to retard its retrogradation. The force at fracture of rice cake samples containing sucrose but no D-psicose increased after refrigerated storage, while that of the samples containing D-psicose or trehalose remained largely unchanged. Both the gelatinization temperature and enthalpy determined using differential scanning calorimetry were lower in the presence of D-psicose than sucrose or trehalose. X-ray diffraction peaks arising from crystalline structures in starch disappeared upon heating up to 68 degrees C in the presence of D-psicose and 75 degrees C in the presence of sucrose or trehalose. The reduction in the dielectric relaxation strength due to starch retrogradation was more pronounced in the presence of sucrose or trehalose than D-psicose. The present results suggest that D-psicose facilitates melting of the crystalline structure in rice flour upon heating and inhibit re-crystallization during storage.