龍眼干燥特性之研究

Fundamental Studies on Longan Drying

洪滉祐(Huaang-Youh Hurng)

《農業機械學刊》 6卷1期 (1997/03) Pp. 71-84

https://doi.org/10.30062/JAM.199703.0006

摘要

乾燥是龍眼鮮食以外主要加工處理製程（林，1989），乾燥作業與前處理、風溫、風速、風量及濕度均息息相關。本研究藉由龍眼鮮果乾燥前的殺菁處理、冷卻方式及熱風溫度的控制，探討基礎乾燥特性；並進而由改善傳統製程劣點的品質指標，擇優條件進行控制濕度之乾燥作業。
乾燥倉內濕度以除濕輪配合冰水機加以控制，藉矽膠的吸附及脫附作用產生極低濕乾空氣（約RH2.5%）進行乾燥。由試驗結果顯示，殺菁前處理提高龍眼於乾燥製程凹陷度及乾減率，但降低果殼抗壓强度。殺菁條件中以100℃熱水殺菁30秒後冷水冷卻使果殼白度值(W.I.)最高。乾燥初溫高於80℃時，凹陷度顯著提高。同溫下固體除濕法乾燥可得較大之乾減率，乾燥時間縮短且品質指標顯示其乾燥品優於電熱烘箱乾燥品。

關鍵字

龍眼 ； 殺菁處理 ； 熱風干燥 ； 固體除濕乾燥

並列摘要

Drying is the main processing of fresh Longan fruit. The drying operation relates to the pre-processing, air velocity, air volume and environment humidity closely. This study is to investigate the fundamental drying property of fresh Longan fruit before drying under the control of blanching processing, cooling method and hot-air temperature. It can improve the quality index of traditional drying processing and offer the optimal conditions to control humidity for drying processing.
The humidity of drying cabin was controlled by dehumidified wheel and ice water machine. The lowest humidity dry-air (about RH 2.5%) was produced by the sucking and escaping functions of silicon gum. From experimental results, the blanching preprocessing during Longan drying induced the increase of concavity and drying rate. But the compression resistance of fruit shell decreased. The blanching condition was blanched by 100℃ hot water, after that30 seconds the cold water cooled continuously to increase the white intensity of fruit shell. The concavity degree was increased as the drying temperature greater than 80℃. The solid desiccant dehumidification drying method can obtain larger drying rate at same temperature and reduce the drying time. The quality index of drying product on solid desiccant dehumidification drying was better than that on electric heating oven drying.

並列關鍵字

Longan ； Blanching ； Hot-air drying ； Desiccant-dehumidification drying