Quality Parameters and the Modeling of the Microwave Drying Kinetics of Basil 'Nufar' (Ocimum basilicum L.) Leaves

Basil is a highly valued aromatic plant worldwide, and drying is one of the best ways to preserve its leaves. Through a theoretical approach, the microwave drying of basil leaves can be modeled, and the effective diffusivity can be determined. However, using a model that considers moisture diffusion in the presence of intensive microwave energy is crucial. This study proposed a theoretical model to simulate the microwave drying of basil leaves in a thin layer. The model assumed that the material is homogeneous and isotropic, with the effective diffusivity depending on the microwave power. The model was solved numerically and validated with experimental data. The study also examined the effect of the microwave power on the color and bioactive properties during drying. The drying time was reduced by 60%, by increasing the microwave power from 199 W to 622 W. The effective diffusivity was found to be directly proportional to the microwave power. Drying at low powers was found to cause basil pigment degradation. However, drying at a power of 622 W resulted in better preservation of the leaves without browning. Finally, microwave drying negatively affects the bioactive compounds, as the phenolic content and antioxidant capacity in all the powers evaluated were significantly lower than in fresh basil leaves.