Optimization of drying condition for brown rice with low moisture content

Optimal drying condition of brown rice was discussed for the low-moisture-content storage. A 100 g of brown rice samples with 15.5% moisture content wet basis (m.c.) was dried to 10.0% m.c. at 40, 50, 60, and 70 degrees C by thin-layer drying. The germination rate of the brown rice dried at 70 degrees C decreased, and drying operation did not affect the germination rate of the rice dried at 40-60 degrees C. In addition, we discussed changes in cracking rate of brown rice after drying. Regardless of drying temperature, the cracking rate was less than 1% soon after drying. The cracking rate, however, changed with the passage of time, and depends on drying temperature; the rice dried at 30 degrees C has less than 1% of cracking rate after 72 hours, the cracking rate of the rice dried at 50 and 60 degrees C increased until after 48 hours, and that of the rice dried at 70 degrees C continued to increase for 72 hours. Finally, the Effect of drying condition on cracking rate was researched by drying samples at a combination of 30, 40, 50 degrees C and 5-10, 15-20, 25-30% of relative humidity (RH). From the results, it was suggested that drying temperature more affected the cracking rate than relative humidity in drying brown rice with 15.5% m.c. This suggestion was confirmed by multiple linear regression analysis. The optimal condition for drying brown rice from 15 to 10% m.c. was 40 degrees C and 5-20% RH from the viewing point of keeping rice quality and decreasing drying time.