Effects of postharvest operations on the gelatinization and retrogradationproperties of long-grain rice

The effects of rough rice pre-drying, drying, and storage treatments on the gelatinization and retrogradation properties of long-grain rice (cv. Cypre ss) were studied via differential scanning calorimetry (DSC). The experimen tal variables included two pre-drying conditions (immediate and delayed dry ing), two drying conditions thigh and low air temperatures), and four stora ge treatments (no storage, and storage at 4, 21, and 38 degrees C for 20 wk ). Gelatinization of the rice flour in water occurred at temperatures from 73 to 86 degrees C, with an enthalpy of 8.3 to 9.7 J/g. Storage temperature had a significant effect on the gelatinization characteristics. Rice store d at 38 degrees C exhibited higher (p < 0.0005) gelatinization enthalpy and peak temperature than did rice stored at 4 and 21 degrees C. Pre-drying tr eatments had no significant effect on the gelatinization enthalpy and peak temperature, but did on the onset temperature (p < 0.05). The pre-drying an d/or drying treatments had significant (p < 0.05) effects on the retrograda tion onset and conclusion temperatures of gelatinized rice. Storage of roug h rice significantly (p < 0.0001) increased retrogradation enthalpy, but di d not affect the peak temperature of the retrogradation endotherm.