Assessment of moisture adsorption and desorption isotherms, hysteresis phenomenon and thermodynamic analysis of habanero chili (Capsicum chinense) powder

Moisture adsorption and desorption isotherms (MSIs) of habanero chili powder were determined at different temperatures (20-55 °C) and water activities (a_w; 0.10-0.90) using the Dynamic Vapor Sorption (DVS) method and applying the conditions typically used during the storage, packaging, and drying of habanero chili. The MSIs were sigmoidal (Type II); the best fit models were GAB and Peleg. The sorption capacity of habanero chili powder decreased with increasing temperature and constant a_w, becoming less hygroscopic. The hysteresis phenomenon was observed for all the temperatures evaluated. Thermodynamic properties were strongly dependent on the equilibrium moisture content (EMC). The net and total isosteric heat were higher for desorption than for adsorption, in both, they decreased as EMC increased. Sorption entropy and Gibbs free energy also decreased with rising EMC. Furthermore, the sorption surface area (SSA) decreased with increasing temperature. This information is essential to know the optimal storage and processing conditions to preserve the quality and prolong the shelf life of habanero chili powder.

Keywords: Goat´s milk, Mexican manchego-type cheese, microstructure, rheological properties, thermal analysis, TPA.