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) 100g(DM)(-1)) and 6 kg/h CO2-10% EtW (2527 mg(GAE) 100g(DM)(-1)). At 6 kg/h CO2-10% EtW flow rate the amounts of monomeric (188 mg(catechin) 100g(DM)(-1)) and oligomeric (154 mg(catechin) 100g(DM)(-1)) fractions of PAs, as well as their antioxidant activity (809 and 546 Mg alpha-tocopheroll 100g(DM)(-1)) were higher than at 4 kg/h CO2-7.5% EtW-flow rate. SC-CO2 methods were compared with conventional methanol extraction.