New insights into the thermal degradation behavior of Hydroxypropyl-beta-cyclodextrin inclusion complexes containing carvacrol essential oil via thermogravimetric analysis

The physicochemical properties and thermodynamic parameters of cyclodextrin inclusion complexes (ICs) containing essential oil were investigated by thermogravimetric analysis. It is necessary to understand the ICs’ thermal decomposition behavior and kinetics to control and elucidate the inclusion complexation mechanisms. Carvacrol essential oil was encapsulated with hydroxypropyl-beta-cyclodextrin (HP- β CD) using the freeze-drying method. The IC was characterized by SEM, FT-IR, and phase solubility, which confirmed that there were molecular interactions between the carvacrol essential oil and HP- β CD. Moreover, thermal experiments were carried out by a thermogravimetric analyzer at different heating rates (10–40 °C min −1 ). In addition, three different models, i.e., FOW, KAS, and Starink, were used to calculate the kinetic energy. The FOW was a more proficient model for the calculation of activation energy (E a ). Further, the average values of E a varied from conversion, and for carvacrol, HP- β CD, and carvacrol/HP- β CD IC, they were found to be 70.56, 162.15, and 152.57 kJ mol −1 based on the FOW model, respectively. In general, carvacrol encapsulated into HP- β CD as an IC showed high thermal stability. The kinetic results could be useful in predicting the thermal performance of IC and in helping optimize experimental procedures for the encapsulation of essential oils in cyclodextrins. Graphical abstract