Quality Evaluation of Long-Term Stored Rice by Pasting Properties

Abstract

Rough rice (cv. Hatsushimo) was stored at four moisture contents (MCs) of 11.1, 12.8, 14.7, 17.6% and three temperatures of 4, 20 and 35°C for up to 17 months. During storage, the overall pasting properties of the rice flour changed depending on storage conditions. For the rice stored at 4°C, the peak viscosity was almost constant during the first storage period after which it increased slightly, but setback viscosity and final viscosity remained constant. Increases in the peak viscosity, setback viscosity and final viscosity were observed in the rice stored at 20°C. The rapid changes in these parameters were observed particularly in the rice stored at 35°C. The MC also affected the rate of change. The pasting temperature did not change in the rice stored at 4 and 20°C for all MC levels, but started to increase rapidly after 3 to 9 months at 35°C. A statistical analysis showed a complicated influence of storage period, temperature, MC and their interaction to the pasting properties of long-term stored rice.