Subcritical Solvent Extraction of Procyanidins from Dried Red Grape Pomace

Procyanidins in dried Sunbelt (Vitis labrusca L.) red grape pomace were extracted using accelerated solvent extraction (ASE) with pressure (6.8 MPa), one extraction cycle, and temperature (40, 60, 80, 100, 120,, and 140 degrees C). Six ethanol/water solvents (0, 10, 30, 50, 70, and 90%, v/v) were compared to conventional extraction with acetone/water/acetic acid (70:29.5:0.5, v/v/v). Procyanidins in the extracts were identified by HPLC-ESI-MS/MS and contained degrees of polymerization (DP) of 1-5 (monomers through pentamers) and polymers (DP > 10). Generally, 50% ethanol/water (v/v) extracted more total procyanidins than other ethanol/water compositions, and contained up to 115% of total procyanidins extracted by the acetone-based conventional solvent. Additionally, 50% ethanol/water (v/v) extracted 205, 221, and 113% more epicatechin, catechin, and dimers, respectively, than conventional extraction. Results indicated greater extraction of low oligomeric procyanidins using 50% ethanol/water (v/v) solvent between 80 and 140 degrees C.