Modelagem matemática e determinação do coeficiente difusivo do processo de secagem de folhas de Malva sylvestris L.

Abstract

Drying is one of the ways to increase durability and preserve the quality of several types of products. This technique is particularly relevant regarding plants used for medicinal purposes. Malva sylvestris L., also known as mallow, is an example of such therapeutic plants originally native from Europe, Northern Africa, and Asia. Mallow is used in different pathologies, especially for the treatment of inflammations. Due to the lack of information on the process of drying the mallow leaves, the present work aims at evaluating the kinetics of mallow leaves drying. Its diffusion coefficient was determined and seven mathematical models were fitted to experimental data on the moisture ratio. The leaves were dried under controlled conditions (i.e. at 30, 40, 50, qnd 60 °C) until reaching the equilibrium moisture. The fit of models to experimental data were performed according to Levenberg Marquardt method with the software SciDAVis 2.4.0. The best fitted model was inferred via analysis of the explanation coefficient (R2), mean relative error (P), standard error (SE), and Qui-square test (X2). The results show that Wang & Singh was the model that best fitted the experimental data of leaf drying. It was observed that, with the increases in the temperature of drying air, the effective diffusion coefficient increased, which allowed better drying. Using Arrhenius equation in a linear equation, it was possible to evaluate the influence of the temperature on the effective diffusion coefficient. The amount of 38 001 kJ mol-1 was obtained as activation energy for the drying process of mallow.