Moisture sorption isotherms of dehydrated (African oil bean) Pentaclethra macrophylla benth. cotyledons

Abstract

Sorption isotherms of (African oil bean) Pentaclethra macrophylla benth. cotyledons were determined by static gravimetric method at different temperatures, in the range from 28 and 48 ^oC. Equilibrium moisture content (EMC) data were analysed using various sorption models usually applied to dried food materials. Experimental data were analysed by a thermodynamic approach to obtain such properties as net isosteric heat, net equilibrium heat, differential and  integral entropy that provide a deeper understanding of the properties of water and energy requirements associated with sorption process. Sorption isotherms of dried African oil bean cotyledons showed type II isotherm. Adsorption and desorption isotherms were best described by Guggenheim–Anderson-DeBoer (R² = 0.98). Monolayer moisture ranged between 0.09 and 0.99 gH₂O/100gDM. The monolayer moisture content decreased as temperature increased. Isosteric heat and entropy of sorption value decreased with increase in moisture content of the oil bean cotyledons.