Hygroscopic and thermodynamic behavior of carob fruit and leaves

Determination of sorption isotherms is a very important step in food processing. These curves are a plot of the moisture content of the food as a function of water activity (aw). Valuable information could be extracted from sorption data, for drying, storage, and packaging. Our aim is to develop adsorption and desorption isotherms for carob fruit and leaves (Ceratonia siliqua L.) at 30, 40, and 50 C using the standard static gravimetric method. The sorption isotherms visualized a type II shape according to Brunauer-Emmet-Teller (BET) classifications. A hysteresis effect existed over the range of water activity at the tree studied temperatures. The model fitting was evaluated using several statistical parameters. The Belahovec & Yanniotis and Guggenheim-Anderson-de Boer (GAB) models have described the sorption curves properly. The net isosteric heat of sorption and sorption entropy decreased with an increase in equilibrium moisture content. The enthalpy-entropy compensation theory was verified for the studied products.