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The present work deals with modeling the kinetics of essential oils extraction from plant materials by water and steam distillation. The experimental data were obtained by studying the hydrodistillation kinetics of essential oil from juniper berries. The literature data on the kinetics of essential oils hydrodistillation from different plant materials were also included into the modeling. A physical model based on simultaneous washing and diffusion of essential oil from plant materials were developed to describe the kinetics of essential oils hydrodistillation, and two other simpler models were derived from this physical model assuming either instantaneous washing followed by diffusion or diffusion with no washing (i.e. the first-order kinetics). The main goal was to compare these models and suggest the optimum ones for water and steam distillation and for different plant materials. All three models described well the experimental kinetic data on water distillation irrespective of the type of distillation equipment and its scale, the type of plant materials and the operational conditions. The most applicable one is the model involving simultaneous washing and diffusion of the essential oil. However, this model was generally inapplicable for steam distillation of essential oils, except for juniper berries. For this hydrodistillation technique, the pseudo first-order model was shown to be the best one. In a few cases, a variation of the essential oil yield with time was observed to be sigmoidal and was modeled by the Boltzmann sigmoid function.

The present paper dealt with the influence of the common juniper berries pretreatment on the yield, chemical composition and extraction kinetics of juniper essential oil (JEO) obtained by classical (HD) and microwave-assisted hydrodistillation (MAHD). The highest JEO yield was obtained by HD from one-minute dry-ground juniper berries (2.23 ± 0.00 g/100 g). No statistically significant influence of swelling and distillation technique on JEO yield was observed. Therefore, the optimal pretreatment process involved no swelling and one-minute grinding. However, no significant difference in the chemical composition of the JEOs obtained by the two techniques was observed. A new phenomenological kinetic model was developed on the basis of the mechanism of JEO extraction by both HD MAHD, which assumed three simultaneously-occurring stages: washing, unhindered diffusion and hindered diffusion. The main advantage of developed model was its ability to describe the variations of JEO yield and distillation rates with time. Furthermore, it had the smallest mean relative percentage deviation compared to the well-known kinetics models and the parameters that all were statistically significant, so it was recommended for modeling the kinetics of JEO extraction by HD and especially MAHD. [ABSTRACT FROM AUTHOR]