High pressure solvent extraction of maritime pine bark: Study of fractionation, solvent flow rate and solvent composition

Maritime pine bark, an abundant Portuguese residue rich in high-value phenolic compounds, was subjected to fractionated and non-fractionated high pressure extractions (F-HPE and NF-HPE, respectively). Supercritical carbon dioxide (scCO2) was the chosen solvent to extract the pine bark low-polarity fraction and ethanol (EtOH) was added to scCO2 to recover the phenolic fraction. The effect of the solvent flow rate was studied on first step (scCO2) and second step (CO2:EtOH 90:10, v/v) F-HPE kinetics. Due to the low first step yield (0.6–1.0%, d.b.) HPE was further performed with no fractionation at 303 K and ∼25 MPa. The flow rate that achieved the highest global yield (7.6 × 10−5 kg/s) was chosen to carry out NF-HPE with different EtOH compositions (30–90%, v/v). The HPE results were compared with hydrodistillation and Soxhlet extraction results in terms of global yields, extracts compositions and extracts antioxidant activities. The results showed that fractionation, solvent flow rate and solvent composition affected extraction kinetics and the characteristics of the extracts. In particular, the solvent composition CO2:EtOH (30:70) led to the extract with the highest contents of total phenolic compounds and of procyanidins (25.6% and 19.8%, respectively), being similar to the ones achieved by Soxhlet extraction (26.0% and 18.2%, respectively). The HPE methodology takes advantage over the conventional methodology due to the reduced EtOH consumption, lower solvent-to-solid ratio, lower extraction temperature, and oxygen-free medium in which it occurs.