Drying Kinetics and Quality Attributes of White Radish in Low Pressure Superheated Steam

In this paper, white radish discs were dried in superheated steam at absolute pressure 95 mbar at four levels of drying temperature from 75 degrees C to 90 degrees C. The drying kinetics and various quality attributes of white radish were investigated, compared with the results by vacuum drying. By kinetic modeling of drying processes with Fick's second law, low pressure superheated steam drying (LPSSD) had slightly lower value of effective moisture diffusivity but higher activation energy than vacuum drying. In comparison with vacuum drying, the rehydration capability of dried samples by LPSSD was better due to porous microstructure. Only 25 % or more the total amount of Vitamin C was preserved after drying to the ultimate moisture content, but it was found that some amount of Vitamin C was taken with the exhaust steam and preserved in the condensate.