Currently in Taiwan the traditional method of open sun drying is still practiced and many agricultural and food products, e.g. persimmons, Hsin-Chu rice noodles, Guan-Miao noodles, and other preserved foods are processed using this method. For these products, exposure to sunlight is required so that a characteristic flavor can be achieved. However, the process is complex and poses problems of hygiene; also, a very humid climate causes product quality to fluctuate. In the drying process, the agri-food product undergoes continuous, volumetric, physical and chemical changes. It was noted by
Hatamipour and Mowla (2002), that humidity has a decisive influence on drying rate. Besides, a relatively high temperature at the beginning will cause ‘‘case hardening.’’