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Evaluation of thermodynamic properties using GAB model to describe the desorption process of cocoa beans
Author(s) -
de Oliveira Gabriel Henrique Horta,
Corrêa Paulo Cesar,
de Souza Santos Emílio,
Treto Pedro Casanova,
Diniz Mayra Darliane Martins Silva
Publication year - 2011
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1111/j.1365-2621.2011.02719.x
Subject(s) - equilibrium moisture content , desorption , thermodynamics , enthalpy , gibbs free energy , chemistry , relative humidity , water content , humidity , entropy (arrow of time) , moisture , sorption , physics , organic chemistry , adsorption , geotechnical engineering , engineering
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.