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ABSTRACT BACKGROUND Microwave-assisted hydrodistillation ( MAHD) has widely been used to isolate essential oil from various plant materials, but it has not been applied yet to extract essential oil from juniper berries. The main goals of the present work were to establish a model describing the extraction kinetics and the chemical composition of the essential oil obtained. RESULTS A lower final essential oil yield from juniper berries was obtained by MAHD than by conventional hydrodistillation ( HD). No significant differences in chemical compositions of the essential oils extracted by the two techniques were observed. The mechanism of both processes was the same and included fast (washing) and slow (diffusion) distillation of essential oil that occurred simultaneously. CONCLUSION The kinetic model involving simultaneous washing and diffusion of essential oil was verified for various plant materials (areal parts of savory and thyme, fennel seeds and juniper berries) for both MAHD and HD that indicated its general importance. For the first time, the kinetic models of MAHD and HD were compared. Knowledge of the juniper berry essential oil yield and the extraction kinetics is of importance from the technological and economics points of view, while the chemical composition determines its use. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The present work deals with the modeling of 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 ., 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 mate- rials. 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 model is the one 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. [ABSTRACT FROM AUTHOR]