青蔥低溫低濕乾燥之研究

Study of Low Temperature Low Humidity Drying for Scallion

林佳穎(Chia-Ying Lin) ； 李紘宥(Hung-Yu Lee) ； 吳柏青(Po-Ching Wu)

《宜蘭大學生物資源學刊》 6卷1期 (2010/12) Pp. 9-15

https://doi.org/10.6175/job.2010.61.12

摘要

青蔥是國人料理中不可或缺的重要食材，然而其栽種易受天候災變影響，造成供貨不穩、價格波動不定。因此利用乾燥加工方式處理，以穩定供應並維持青蔥價格。由於冷凍乾燥作業成本較高，本實驗採用低溫低濕乾燥技術，分別以25°C、35°C、45°C低溫低濕空氣進行乾燥試驗。實驗採用宜蘭縣三星地區生產之小憨種青蔥，針對低溫低濕乾燥青蔥樣品之含水率、顏色及復水性質進行檢測，並與熱風乾燥及冷凍乾燥青蔥樣品進行比較，以瞭解其產品品質。結果顯示25°C低溫低濕乾燥之時間最長，且不同的乾燥方法對蔥白之白度及蔥綠之Hunter-a值有顯著的影響。將不同乾燥法處理後之乾燥產品及復水後之青蔥與生鮮青蔥產品進行比較a值及白度，結果顯示以35°C低溫低濕乾燥為最接近生鮮青蔥品質之最佳條件。此外，低溫低濕乾燥機內部風場及溫度分佈不均勻，造成各層的合水率不均勻，建議針對機體內部風場及溫度分佈進一步改善。計算不同乾燥方式之乾燥成本（元/kg），結果顯示冷凍乾燥、50°C熱風乾燥、25°C低溫低濕乾燥、35°C低溫低濕乾燥及45°C低溫低濕乾燥之乾燥成本分別為2675.66元/kg、55.14元/kg、141.20元/kg、164.10元/kg及113.54元/kg。冷凍乾燥雖然有最佳品質，但其成本過高，不符合經濟效益，而若欲達到兼顧品質（顏色接近生鮮青蔥）與成本（低成本高效率）之最佳狀態，則以35°C低溫低濕乾燥為乾燥條件最佳。

關鍵字

青蔥 ； 低溫低濕乾燥 ； 復水

並列摘要

The scallion is an important food material for people cooking in Taiwan, nevertheless the weather conditions will affect the scallion growing. This will cause the supply of scallion and the stability of prices. In order to stabilize the scallion supply and price, drying processes were used. This study was to study the low temperature low humidity drying technique, low temperature (25°C, 35°C, 45°C) low humidity air were used for drying experiments. The Xiao-Han variety scallion samples which grown in the Ilan county Sunshin area were used in the drying experiment. Comparing with the hot air and freeze dried samples, the moisture content, color and rehydration character of low temperature low humidity dried scallion samples were determined to evaluate the quality of dried products. The experiment results indicated that 25°C-LTLR (low temperature low humidity drying) took the longest drying time. The drying methods significantly affect the whiteness index of white leaf portion and the Hunter-a value of green leaf portion. The whiteness index and Hunter - a value of rehydrated samples were compared with the fresh scallion sample. The experiment results indicated that the sample dried with 35°C-LTLR had the best quality comparing with the fresh scallion sample. Besides, the wind field and temperature distribution inside the LTLR dryer were quite uneven, and these would cause uneven moisture content at each layers. Therefore, the internal wind field and temperature distribution should be improved in the further study. The drying costs for various drying methods were evaluated. The drying cost for freeze drying, 50°C-hot air drying, 35°C-LTLR, 45°C-LTLR, and 25°C-LTLR were 1,376.4 NTD/kg, 55.1 NTD/kg, 35.2 NTD/kg, 33.5 NTD/kg, and 28.0 NTD/kg, respectively. Although the freeze dried samples had the best quality, its drying was too high to use. Considering both the drying quality and cost, 35°C-LTLR was the optimal condition to used.

並列關鍵字

Scallion ； Low temperature low humidity drying ； Rehydration