oxide extractor (Natex, Prozesstechnologie GesmbH, Austria, Fabr. no.
10-023/2011) comprising a 2.0-L cylinder extraction vessel and two
separators (S40 and S45) each with 1.5-L capacity. The extractor basket
was filled with ~0.320 kg of grinded dried thyme leaves for each
extraction. During extraction, the solvent (CO2, 99.99% purity supplied
by Messer S.A., Romania) was constantly chilled to remain liquid and
recirculated. The solvent was brought to supercritical conditions at
7.30 MPa, and a flow rate of 21.65 ± 0.10 kg/h, as indicated by the
data sheets from ABB software (ABB - Mannheim, Germany). For all extractions
the temperature in the extraction vessel was set at 40 °C and
each extraction was performed during 240 min. Two extraction pressures
were applied, 30 MPa and 40 MPa (Bermejo et al., 2014). In
order to produce fractions with different composition, the pressure in
the first separator (S45) was maintained at 10 MPa, while in the second
separator (S40) decompression up to recirculation pressure of 5 MPa
was set (Santoyo, Jaime, García-Risco, Lopez-Hazas, & Reglero, 2014).
The two steps decompression in the end of the extraction produced
four extracts (S40.1 and S45.1 at 30 MPa, respectively S40.2 and S45.2
at 40 MPa) which were collected in dark bottles and kept under refrigeration
conditions (2–4 °C) until further use in experiments. The extractor
was fed in three batches and the extracts were collected all at once at
the end of the process.