Moisture sorption isotherm of microencapsulated extra virgin olive oil by spray drying

Adsorption isotherms, at 4, 25 and 60 degrees C for microencapsulated extra virgin olive oil powder (MEVOP) prepared by rotor-stator homogenization (RSH) and ultrasonic homogenization (UH) methods before spray drying, were obtained using standard static gravimetric method. The sorption isotherms exhibited type III (J shape) behaviour. The sorption isotherms of MEVOP depended on temperature, chemical composition of particle surface and particle size of samples. The equilibrium moisture contents (EMC) decreased with increasing temperature. The sorption isotherm of MEVOP obtained with UH shifted up compared to that obtained with RSH because of the smaller particle size of MEVOP obtained with UH. The Guggenheim-Anderson-de Boer (GAB) model was the best fitting the experimental sorption data. Monolayer moisture contents of MEVOP were in the range of 0.036-0.079 kg H2O per kg d.s. All K values of MEVOP were higher than 0.89. C values of MEVOP obtained with RSH and UH method varied in range of 7.17-13.86 and 8.42-27.76, respectively. Net isosteric heat of sorption was evaluated using the Clausius-Clapeyron equation and differential entropy decreased with increasing moisture content. Gibbs-free energy decreased with increasing equilibrium moisture content. The spreading pressure increased with the rise in water activity for all temperatures.