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均化對稻榖薄層乾燥速率之影響
Tempering Effect on Drying Rate of Rough Rice
摘要
每樣品重50公克之中粒種稻穀放置在一有12乾燥筒之樣品乾燥機上作階段式乾燥，乾燥熱風溫度有50°，45°，40°和35℃四種，均化時間分350，75和0分鐘三種，每階段乾燥爲時10分鐘，風量2.32 cmm／kg，穀層厚度約1-2粒穀厚，共4×3處理，每處理3重複。 試驗結果顯示：所有處理之第一回乾燥之減乾率都很高，但如果沒有均化時間，穀粒內部水分移動之限制立刻反應在第二回乾燥上。 所有乾燥曲線在半對數座標上，除最初1-2點之外，均大致顯示直線之特性。 將稻穀用50℃熱風、自36％烘乾至17％(d.b)，扣除均化時間、就實際乾燥時間而言，三種不同均化時間處理之結果分別爲：150、80、和60分鐘；均化時間長，需時短。若均化時間計算在內，依0 min／75 min／350 min三個不同均化時間次序、每種均化處理內四種不同溫度處理之平均減乾率分別爲6.02，1.84和0.58％／hr。 均化時間之長短對乾燥後期之減乾率之影響顯而易見：三種不同均化時間處理(0 min, 75 min, 350 min)之最末一回之平均減乾率分別為：0.50％，0.95，和1.76％。 熱風溫度在乾燥初期對減乾率有決定性之影響，但在乾燥後期，同一均化時間之不同溫度處理之減乾率均趨向一致。
並列摘要
Medium rough rice of 50 grams lots were step-dried in a 12-drying-cell sample dryer, with drying-air temperatures of 50℃, 45℃, 40℃ and 35℃, and with 350 min, 75 min, and 0 min tempering periods between drying steps. The drying air flow rate was 2.32 cmm/kg. The grain layer was about 1-2 grains thick. There were 4×3 treatments with 3 replicates for each treatment. High drying rate were observed for the first 10 minute-round drying for every treatment, but the limitation of internal moisture movement within the grain imposed its influence immediately for the following rounds of drying in the non-tempering treatments. On semi-logarithm coordinates, the drying curves approach linear with exception for the first one to two rounds. If tempering time was not counted, the time periods required to remove rice moisture from 36%(d.b.) to 17%(d.b.), using 50℃ air, were 150, 80, and 60 minutes for the three tempering treatments, respectively. The longer the tempering, the less time was required. If the tempering periods were counted, the average drying rates for all temperature treatments were calculated to be 6.02, 1.84 and 0.58%/hr, for the three tempering of 0 min, 75 min, and 350min. The tempering effect on the drying rate at the final stages of the drying was evident. The amounts of drying at the last round drying were 0.50%, 0.95%, and 1.76% for 0 minute, 75 minutes, and 350 minutes, respectively.