Thermodynamic properties of moisture sorption of soybean (Glycine max L.) grains

This study investigated the thermodynamic properties of water sorption in soybean using the DM 68I69 Ipro variety from Campo Verde, Mato Grosso, Brazil. Grains with initial moisture contents of 21.95% (w.b.) and 3.50% (w.b.) were used for desorption and adsorption analyses, respectively. The static-gravimetric method determined equilibrium moisture content at various temperatures (10, 20, 30, 40, and 50°C) and relative humidity (between 0.11 and 0.92 ± 2%). The Modified Halsey model quantified the hygroscopicity of soybean. Key findings include: (a) desorption equilibrium moisture content exceeded adsorption values, demonstrating hysteresis; (b) decreasing equilibrium moisture content increased the energy required for water removal and its release during adsorption; (c) differential entropy of desorption and adsorption increased with decreasing equilibrium moisture content; (d) Gibbs free energy decreased with increasing temperature for both desorption and adsorption. The enthalpy-entropy compensation theory effectively described the observed phenomena.