Optimization of drying condition for brown rice with low moisture content
2007
Genkawa, T.(Kyushu Univ., Fukuoka (Japan)) | Inoue, A. | Uchino, T. | Tanaka, F. | Hamanaka, D.
Optimal drying condition of brown rice was discussed for the low-moisture-content storage. A 100g 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 deg C by thin-layer drying. The germination rate of the brown rice dried at 70 deg C decreased, and drying operation did not affect the germination rate of the rice dried at 40-60 deg 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 deg C has less than l% of cracking rate after 72 hours, the cracking rate of the rice dried at 50 and 60 deg C increased until after 48 hours, and that of the rice dried at 70 deg 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 deg 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 deg C and 5-20% RH from the viewing point of keeping rice quality and decreasing drying time.
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