Kiyokazu Goto

Effects of Heat Shock Treatment on Rice Quality during Storage (Part 2)- Nutritional and Pasting Properties Changes -

Abstract Heat shock treatments (HSTs) using microwave radiation were performed on harvested rice (cv. Koshihikari) up to 60, 70 and 80°C, and kept additionally for 0, 1 and 3 min, following drying and storage at 40°C for 6 months. For control rice, during storage there was a decrease in protein and starch digestibility, increase in setback viscosity (SV), final viscosity (FV) and pasting temperature (PT), while peak viscosity (PV) increased rapidly for the first 2 months then decreased. The HSTs at 70 and 80°C were effective in maintaining a high value of starch digestibility and low value of PV during storage, while the HSTs at 60°C retarded changes of PV and FV values. The results showed that HST would benefit quality maintenance of stored rice.

Effects of Heat Shock Treatment on Rice Quality during Storage (Part 1)- Changes in Starch Components and Fat Acidity -

Abstract Harvested rice (cv. Koshihikari) was microwave-radiated up to 60, 70 and 80°C and kept heat-treated for 0, 1 and 3 min, dried and then stored at 40°C for 6 months. A pronounced change in chemical properties of control rice during storage was observed such as increase in fat acidity, soluble sugars, total amylose and insoluble amylose content, while a decrease was founded in total starch content, and soluble amylose content. The above changes also occurred in heat shock treated rice, but with certain extent of delay. The heat shock treatment (HST) delayed the increasing rate of fat acidity. The HSTs at 60 and 70°C were effective in keeping the values of total amylose and insoluble amylose content low. The results showed that HST would benefit rice quality maintenance during storage.