Modeling drying kinetics of dominga grapes

Abstract

Air drying kinetics of grapes (Dominga variety) were determined at 30, 40 and 50°C and velocities of 0.45 and 0.60 m/s, using a pilot tunnel tray drier. The air relative humidity ranged from 3 to 35%. The characteristic drying curves presented a single falling-rate behavior. Several models were attempted to fit the drying data. The effect of temperature on grape drying kinetics was also quantified. Air velocity had no significant effect on drying rates, in the tested range. The exponential model presented the best fit, and a drying rate and equilibrium moisture content were obtained for each isothermal experiment Temperature influence on drying rate followed an Arrhenius type behavior. A one-step non-linear regression to all the data allowed to obtain an activation energy of 31.8 :!:0.3 kJ/mol and a mean equilibrium moisture content of 0.338 :!:0.007 kg water/kg d.m. The developed model is crucial for simulating drying times of Dominga grapes.