Effect of intermittent microwave convective drying on quality characteristics of persimmon fruit

Abstract

The present study investigates the quality parameters of dried persimmon (Diospyros kaki) fruit slice by the application of intermittent microwave convective drying (IMCD) method. For the experiment four microwave power 200, 300, 400 and 500 W and three pulse ratio cycle (PR) 1:5, 1:10 and 1:15 were used. Total of 12 experimental runs were conducted with different combinations of selected microwave power and PR to reduce the moisture content of persimmons fruit slice from 90±2% (w.b.) to a safer limit of around 9.86±1.62% (w.b.). Out of all the experimental runs the sample dried at microwave power of 500 W and PR of 1:5 found to have shorter drying time of 66 min and the longer drying time of 208 min was observed for the sample dried at 200 W and PR of 1:15. The functional properties such as total phenolic content (TPC), antioxidant activity and total flavonoid content (TFC) decreased as drying progressed whereas the physical quality parameter change in color was increased with increase in drying time. The functional properties were fitted with first and second order kinetic model, and second order kinetic model found to predict the data with higher accuracy when compared with first order kinetic model. The change in color followed zero order kinetic model with parameter ranging from 0.105 to 0.323min−1. Overall, persimmon fruit slice dried at IMCD condition with power 500 W and PR 1:5 had the highest functional property with lower change in color.