Modeling sorption isotherms and isosteric heat of sorption of roasted coffee beans

The aim of this work was determine the sorption isotherms in roasted beans of specialty coffee at temperatures of 25, 30 and 40 degrees C and water activities between 0.1 and 0.8 using the dynamic dew point method. The experimental sorption data were modeled using 12 different equations to represent the dependence of equilibrium moisture content with a(w) and temperature. The net isosteric heat of sorption was determined from the experimental sorption data using the Clausius-Clapeyron equation. The Weibull model satisfactorily modeled the effect of the temperature on the hygroscopic equilibrium in roasted coffee beans (R-2 (adj) = 0.902 and RMSE = 0.005 kg.kg(-1) d.b.). The net isosteric heat of sorption increase with increased moisture content.