Extraction of proanthocyanidins from grape marc by supercritical fluid extraction using CO2 as solvent and ethanol–water mixture as co-solvent

The extraction of phenolic compounds from grape marc using supercritical CO2 containing 15% ethanol–water mixture (57%, v/v) (EtW) as co-solvent, at 8, 10, 20 and 30 MPa/313.15 K suggested 8 MPa as the most suitable pressure. At 8 MPa/313.15 K, different co-solvent percentages (15, 10, 7.5%) at CO2 flow rate of 6 and 4 kg/h were investigated for proanthocyanidins (PAs) the extraction. The highest extraction yields were obtained at 4 kg/h CO2–7.5% EtW flow rate ( 2600  mg GAE   100   g DM − 1 ) and 6 kg/h CO2–10% EtW ( 2527  mg GAE   100   g DM − 1 ). At 6 kg/h CO2–10% EtW flow rate the amounts of monomeric ( 188  mg catechin   100   g DM − 1 ) and oligomeric ( 154  mg catechin   100   g DM − 1 ) fractions of PAs, as well as their antioxidant activity ( 809   and   546  mg α -tocopheroll   100   g DM − 1 ) were higher than at 4 kg/h CO2–7.5% EtW-flow rate. SC-CO2 methods were compared with conventional methanol extraction.