| Budget Amount *help |
¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2000: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1999: ¥500,000 (Direct Cost: ¥500,000)
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| Research Abstract |
To elucidate the relation between drying rate and fissure occurrence in vacuum drying of raw rough rice with high moisture, studies have been done for three years. The experiments were carried out using suitable combinatiouts : three parameters of vacuum pressure, temperature and relative humidity. Also the raw rough rice was partially used to relate the results of brown rice to rough rice. The results were as follows :
1. With absolute pressures of 5, 40, 75 and 101 kPa (gauge pressure : -96, -61, -26 and 0 kPa) fixed in a vacuum container, drying rates at 5 kPa were remarkably higher than those at weaker set pressures.
2. When the vacuum container was subjected to temperatures of 25, 35 and 45℃ in the air-oven, the effect on drying rate was a notable increase at 45℃ despite lower rates at 25 and 35℃. Thus it is necessary to apply heat together with vacuum pressure.
3. Relative humidity inside the vacuum container dropped due to the evacuation of the humid air. Drying rate then increased a little with the lowering of the surrounding humidity and with increasing vacuum pressure.
4. Whole fissture occurrence, which included surface cracks typically caused in brown rice, increased with the rise in drying rate. However, only a slight degree of internal fissuring occurred. The use of rough rice resulted in conversely less surface crack but higher internal fissure occurrence.
5. Brown rice was easily considered to be injured with air pressure changes because of the rupture of the thin skin film on the grain surface. Nevertheless, the time required for relieving the vacuum was not closely related to surface cracking.
6. Varietal differences in drying rate and fissure occurrence were recognized to be of the same degree as that of heated air drying under normal pressure.
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