Dried muña leaves (Minthostachys mollis): Modeling, kinetics and thermodynamic properties

The muña (Minthostachys mollis) leaf is consumed as an infusion, it has pharmacological properties and is used to relieve digestive and respiratory symptoms. Therefore, drying is important for preservation and storage until use or processing. The aim was to evaluate the influence of drying temperature on kinetics, diffusion coefficient, thermodynamic properties and activation energy. We worked with muña leaves that were subjected to different pretreatments (bleached at 1 % ascorbic acid, immersion in water at 60 °C and without pre-treatment) dried at three temperatures (40, 50 and 60 ° C). The effective diffusion coefficient, activation energy, was determined and the drying process was described using eight mathematical models to represent the drying curve. Thw water content was reduced by the drying process. The Logarithmic model was selected as the one with the best fit to represent the drying kinetics of the muña, the activation energy values were similar between treatments, they did not present significant differences and the increase in temperature promotes: decrease in enthalpy and entropy; increase in Gibbs free energy and effective diffusion coefficient.