Thermodynamic analysis for the hygroscopic behavior of barley seeds (Hordeum vulgare L.)

Abstract

Sorption isotherms aid the analysis of different classes of water to determine the energy required to remove this moisture from seeds. The goal of the present study was to determine and analyze the sorption isotherms for barley seeds. Qualitative and quantitative thermodynamic analysis was performed by GAB model parameters and by calculating the net isosteric heat and differential entropy of sorption. The GAB model successfully described the experimental data. The monolayer equilibrium moisture decreased from 0.092 kg・kg-1 to 0.057 kg・kg-1 as the temperature increased from 15 to 50°C. The net isosteric heat of sorption for the monolayer calculated by the GAB equation parameters exhibited good agreement with that calculated by the Clausius-Clapeyron equation, with values of 2433.0 and 2233.7 kJ・kg-1, respectively. Environmental conditions may have affected the formation of the adsorption sites within the seeds endosperm when compared with literature data. The use of empirical models to fit sorption isotherms may mischaracterize the thermodynamic analysis of the monolayer.