Sorption isotherms and isosteric heats of sorption of whole yellow dent corn

Abstract

The adsorption and desorption isotherms of yellow dent corn were determined at 25, 30 and 37 °C by the gravimetric method. The GAB, Oswin, Halsey, Henderson, Chung-Pfost and polynomial models were fitted to the experimental sorption data. The isotherms exhibited Type II behaviour and were temperature dependent as the equilibrium moisture content decreased with increase in temperature. Hysteresis was also observed at all temperatures investigated. According to the goodness of fit test applied, the GAB model best described the experimental data followed by the Oswin, Chung-Pfost, polynomial and Henderson models. The Halsey model was the least adequate. The monolayer moisture content was found to decrease with increasing temperature, and was higher for desorption than adsorption. The isosteric heat of sorption was determined using the Claussius–Clapeyron equation, and it was found to markedly decrease at the average temperatures investigated with increase in moisture content.