2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

Previous research has shown that high drying and tempering temperatures (60 C) and high moisture removal rates (up to 5 to 6 percentage points moisture content removed per drying pass) can be used without reducing head rice yield, as long as sufficient tempering above the glass transition temperature of the rice is allowed. This previous research, incorporating the glass transition temperature concept, provided insight in rice kernel fissuring during the drying and tempering processes. The next steps in applying this glass transition temperature concept in rice drying and tempering is to 1. Determine the lowest tempering temperature that can be used while maintaining high head rice yields and 2. Determine the tempering durations required for various tempering temperatures. Medium- and long-grain rice was dried under various drying air temperatures (45, 50, 55, and 60 C) for various durations (the durations were aiming at removing 3, 4.5, and 6 percentage points moisture content). After drying, the samples were tempered at various temperatures for various durations. Head rice yield was then determined and plotted against tempering duration. Results show that lower tempering temperatures are feasible, as long as the tempering temperature remains above the glass transition temperature. The results also show that the required tempering duration increases with decreasing tempering temperature.