The kinetics of supercritical fluid extraction of valuable substances from plants depends on both
extract solubility in the solvent (or phase equilibrium between the matrix and the solvent) and mass transfer
resistances, particularly the resistance inside vegetable material. Different mathematical models for supercritical
fluid extraction have been published in the last decades and it can be therefore difficult to choose the most
suitable model for particular extraction. In this chapter, simple criteria based on time constants of mass transfer
and characteristic time of equilibrium extraction are presented, two most frequent types of models for
supercritical extraction from plants are mentioned with references to the literature, and the factors influencing
scale-up of the process are discussed.
