Hot-air drying of whole fruit Chinese jujube (Zizyphus jujuba Miller): physicochemical properties of dried products

Drying characteristics of whole fruit was studied as distinct from fruit slices. Taking Chinese jujube as an example, shrinkage, density, vitamin C, colour and rehydration of whole fruit were measured in hot-air drying at 50, 60 and 70 degrees C. Unlike fruit slices or lumps where shrinkage volume typically equals the volume of removed water, volumetric shrinkage of Chinese jujube was much more than the volume of removed water. Change in shrinkage with moisture content was described using three linear regions. Increased drying temperature increases the retention of vitamin C and the extent of browning, while decreasing shrinkage and the density. The findings are useful for industrial drying of whole fruit of Chinese jujube but also possibly extend to drying of other drupes.