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Evaluation of thermodynamic properties using GAB model to describe the desorption process of cocoa beans

2011; Wiley; Volume: 46; Issue: 10 Linguagem: Inglês

10.1111/j.1365-2621.2011.02719.x

1365-2621

Gabriel Henrique Horta de Oliveira, Paulo César Corrêa, Emílio de Souza Santos, Pedro Casanova Treto, Mayra Darliane Martins Silva Diniz,

Crystallization and Solubility Studies

Summary The desorption isotherms and thermodynamic properties of cocoa beans were obtained during the drying process of this product. The isotherms were determined by dynamic method for various temperature (25, 35, 45 and 55 °C) and relative humidity (RH) conditions (30, 40, 50, 60, 70 and 80%). Equilibrium moisture content data were correlated by the Guggenheim–Anderson–de Boer (GAB) model, which presented good fit to the data, according to statistical procedures. Equilibrium moisture content ranged from 5.90 to 16.67 d.b.; it increased with an increment in the RH and decreased with increased temperature at a constant RH. Enthalpy values for each model coefficient were encountered, ranging from −90.05 to 545.96 kJ kg −1 . The integral isosteric heat of desorption and differential entropy increased with decreased equilibrium moisture content, a tendency also found for Gibbs free energy.