Study of Persimmon Dehydration Using Dehumidification Method

Abstract

本省柿餅製造多在陽光下吹風晾乾，其製程曠廢時日，若受陰雨氣候影響，常有30至70％腐爛率，對果農損失極大，以烘乾機製造柿餅，則有厚皮且脫澀不完全現象。為解決柿餅製造過程中因雨導致之大量腐敗，並製造出優良品質之柿餅，本研究將總量935公斤之柿青，分四批先後逐日置於控制溫濕度之乾燥室中（28-30.5℃、RH 48.3-69.8%)，約經過5個單元循環操作（每個循環為除濕18小時，停機6小時）可以製成柿餅，其較自然日曬法約快兩天。除濕乾燥室中之除濕機除濕能力不足時，會導致乾燥室中濕度上升，隨後發生腐爛，此現象出現在柿青進行乾燥之第三或第四天，即柿子果實開始成熟軟化時。以除濕乾燥法製造柿餅，可以得到與日曬乾燥法所製相同之柿餅色澤，且其色澤呈現均一誘人之金黃色。果糖、葡萄糖為柿餅中主要之糖類，其在乾燥過程中因水分份蒸發而濃度增加，其中又以自然日曬法者較高。柿餅之硬度在除濕乾燥四天後達到最高之530克，自然日曬法製得之柿餅則在乾燥約七天後才達到相同之硬度。柿餅乾燥過程中水活性持續下降，但仍未達常溫下可以保存之程度。 Dehydration of persimmons (Diospyros kaki L.) using dehumidification method at the range from 30℃ to 35℃ and 50 to 65% relative humidity environment resulted in the highest yield and the best quality of dehydrated persimmons, as compared to the products made from conventional sun drying method. Dehumidification of persimmons at above conditions for 18 hours and then turn off the dehumidifier for six hours was the best operation condition for persimmon moisture balance and case hardening prevention. The dehumidification process took five days to remove about 61.3 % moisture of the persimmon. It is two days shorter as compared to sun drying method. Texture of the persimmon decreased to the lowest strength within two days due to fruit softening, and then gradually increased due to water removal and skin formation of dehumidified persimmon. The dehumidified persimmon showed golden color appearance as that by sun drying. Glucose and fructose were the main sugars of persimmon, both of those sugars increased during the drying process. Sun drying persimmon showed a higher amounts of glucose and fructose than the dehumidified persimmon