Determination of thermodynamic properties for vacuum drying of apple slices

The aims of this work were to evaluate the thermodynamic properties of the drying process under different air conditions. The Golden delicious cultivar apples, with an initial moisture content on a dry basis of 0.56 (d.b., decimal), were dried at pressures of 0.2 bar with thicknesses of 5 and 7 mm at three temperatures (50, 60, 70°C) until reaching a moisture content of 0.12 (d.b.). The enthalpy and entropy decreased with increasing temperature, while the Gibbs free energy increased with increasing drying temperature.

Keywords:

liquid diffusivity , enthalpy , entropy , Gibbs free energy