Effects of Freeze-thaw Treatment on Product Quality of Hot Air Drying for Sweet Potato

In order to explore the effects of freeze-thaw treatment on the qualities of sweet potato by hot air drying, the gelatinization properties of sweet potato, changes in conductivity and anthocyanins, and the apparent density, rehydration character, color and hardness of the dry products were investigated. The results show that the sweet potatoes at different freeze-thaw processing were different in gelatinization properties curve, conductivity and anthocyanin content. When treated by one time freeze-thaw cycle, the sweet potato conductivity was the minimum, and anthocyanin content was the highest. With the times of freeze-thaw cycles increasing, the rehydration character of dried products improved, apparent density decreased, and the better color was presented. The products presented the minimum hardness after two times freeze-thaw cycles. This research can provide a theoretical basis for elaborating the mechanism of the freeze-thaw processing to the hot air drying quality changes of the sweet potato.