For food and pharmaceutical applications, high pressure solvent
extraction (HPE) represents an attractive option to conventional
solid–liquid extraction methods and, in some cases, supercritical
fluid extraction can also be applied, offering several advantages in
terms of selectivity, separation conditions and on the use of environmental
friendly technology and solvents. HPE involves the use
of H2O or organic solvents at considerable elevated temperatures
(313–473 K) and pressures (3.3–20.3 MPa), offering the possibility
to perform efficient extractions due to its improved characteristics
in terms of mass transfer and solvating properties. If high
temperatures are applied, the liquid solvent viscosity diminishes,
the solvent diffusivity through the plant matrix is improved and
consequently extraction kinetics is accelerated. Moreover, high
pressure forces the solvent into the matrix pores and hence should
facilitate extraction of target compounds [17]. Therefore, this
extraction technique takes advantage of the beneficial combination
between typical liquids solvation properties and the advantageous
transport properties of supercritical fluids [18]. However, a liquid
separation step is additionally required in the post-extraction
preparation steps, which represents a disadvantage relatively to
the SFE methodology.