Mathematical model for hydrodistillation of essential oils

Hydrodistillation of essential oils was studied using a model with broken and intact cells, in which the solute located in the cells with broken walls is rapidly extracted and the solute from intact cells diffuses slowly to the surface of botanical material. The essential oil is regarded as a pseudo‐component. Model equations describe two types of particles: the leaves, where a part of the solute is deposited on the surface in fragile glandular trichomes, and the ground particles, with initially homogeneous solute distribution. Analytical solution of model equations contains two time constants, the larger one related to essential oil diffusion from the particle core. Using literature data, the model was applied to hydrodistillation of creeping thyme leaves and intact coriander seeds. The effective diffusivity of oil in coriander seed was evaluated as 1.7 × 10−11[sol ]m2[sol ]s. A further model development should respect the different volatilities of essential oil components, leading to changes in the distilled oil composition in the course of the process.