Modeling of desorption isotherms and isosteric heat of sorption in wet parchment coffee beans (Coffee arabica L.)

Abstract

Drying is one of the essential operations to guarantee the stability and quality of parchment coffee beans. The objective of the present work was to model the desorption isotherms of the wet parchment coffee beans by means of a prototype of convective drying at laboratory scale and the estimation of the energy requirement of the process. The experimental data were modeled with three empirical expressions that link the dependence of equilibrium moisture content and water activity with temperature. The net isosteric heat of sorption was estimated by the Clausius-Clapeyron equation. The Iglesias and Chirife model satisfactorily modeled representing the effect of temperature on the isotherms of the wet parchment coffee beans; presented a determination coefficient higher than 0.97 and a root mean square error lower than 0.1 kg kg−1 dry basis, all of which indicate a good fit for practical purposes. The net isothermal heat of sorption decreased with increases in moisture content indicating the net energy expenditure of the drying process.