ISOTHERME D’ADSORPTION D’EAU DES FEVES DE CACAO (THEOBROMA CACAO L.) MARCHAND

Abstract

This study presents the water adsorption isotherms of fermented cocoa beans obtained by drying natural sun. They were determined at 20, 30 and 40 ° C by the static gravimetric method. Equilibrium is obtained after 33 days for the final point. Mathematical models commonly used in the literature to describe the food products have helped explain the hygroscopic behavior during conservation. The regression analysis was performed under the Excel 2013 software, using the non-linear solver GRG algorithm in order to determine the coefficients models. The Guggenheim-Anderson-de Boer model (GAB) of three parameters showed good agreement with the experimental data (r = 0.995, 0.998 and 0.999 respectively for 20, 30 and 40 ° C). The water content of the monomolecular layer is 2.42 and 2.28% at 20 ° C, 2.19 and 2.12% at 30 ° C, 1.99 and 1.90% at 40 ° C for BET and GAB models, respectively. The isosteric heat of net adsorption tends to zero for higher water content (0.053 KJ / mol to 9.28% water). The linearity between enthalpy (net isosteric heat) and differential adsorption entropy shows them compensation.