Effects of various drying conditions and methods on drying kinetics and retention of bioactive compounds in sliced persimmon

Abstract To obtain the predominant drying speed period of sliced persimmon during hot air drying, the aim of this study was to evaluate drying kinetics, effective diffusivity and its activation energy under different drying temperatures (50, 60 and 70°C). Besides, the bioactive compounds, antioxidant activity and microstructure after drying were also compared with those of freeze-dried persimmon. Results showed that water loss of persimmon slices during hot air drying followed the second-order kinetic model. The effective diffusivities of sliced persimmon at 50, 60 and 70°C were 6.45×10-7, 7.48×10-7, and 9.08×10-7 m2 s-1, respectively. No significant (p>0.05) differences in the drying rate at different drying temperatures (50, 60 and 70°C) after 180 min of drying were observed. Contrarily, increase of hot air drying temperature resulted in a significant decreases in majority of bioactive compounds. While, considering the high price and time consumption of freeze-drying technique, as well as the fact that higher drying temperatures did not further affect the drying rate after a certain drying time, controlling the temperature gradient during hot air drying processing might be useful in minimizing energy input and improving the retention of bioactive compounds during the processing of dried persimmon in food industry.