GAB model and the thermodynamic properties of moisture sorption in soursop fruit powder

Abstract

The aim of this study was to model and determine the thermodynamic properties of moisture sorption in soursop
fruit powder. The isotherms were determined by the static method at temperatures of 10, 20, 30, 40 and 50 °C, and a water
activity of between 0.113 and 0.868 (decimal). The GAB model effectively described the moisture sorption phenomenon of
soursop powder. The monolayer moisture content ranged from 12.589 to 9.109% db. The enthalpy values related to the GAB
model were negative, with -2581.035 kJ kg-1 for C0
and -107,758 kJ kg-1 for K0
. The isosteric heat of sorption, entropy and
Gibbs free energy had a high correlation with the equilibrium moisture content, and the correlation between enthalpy and
entropy was confirmed for moisture sorption in soursop powder.