Abstract: In order to improve the freeze-drying efficiency and quality of kiwifruit slices, the effect of slice thickness, pre-freezing method and drying time on the drying rate and quality of kiwifruit slices during freeze-drying process was studied by single factor experiment. The interaction between various factors was analyzed and the regression model of the drying rate of kiwifruit slices is obtained by the response surface method. The results show that the influencing order on the drying rate is drying time, slice thickness, and pre-freezing method. Among them, there was significant interaction between slice thickness and drying time, while there was no significant interaction between slice thickness and freezing mode, freezing mode and drying time. When the traditional single side drying method is used in the experimental freeze-drying equipment, the freeze-drying process of kiwifruit slices is as follows: slice thickness of 5mm, pre-freezing at -20℃, drying for 10h. After the optimization of double-sided drying, the slice thickness can be increased to 7mm, and the drying efficiency can be increased by about 11% at most.

Key words: kiwi slice, vacuum freeze drying, processing parameter, optimization