Effect of cold pressing and supercritical CO2 extraction assisted with pulsed electric fields pretreatment on grape seed oil yield, composition and antioxidant characteristics

The aim of this study was to valorize the oil fraction of grape wine pomace by improving oil yield and sustaining quality. Two "green" extraction methods were applied: supercritical CO2 (SC CO2) extraction, as well as pulsed electric fields (PEF) assisted SC CO2 extraction; and compared with conventional cold pressing. Optimal SC CO2 parameters supporting maximum yield and/or antioxidant capacity were (i) 35 MPa, 45 °C, and (ii) 50 MPa, 35 °C, both at 45 g CO2/min. Two PEF pretreatments at 5 kV/cm and 120 Hz during (i) 5 min and (ii) 1 min were applied. Cold pressing, despite the lower extraction yield (67.1 ± 0.2 g/kg), extracted significantly higher concentrations of tocochromanols, hydrophilic antioxidants and major fatty acid, linoleic acid. Both parameters of PEF pretreatments and SC CO2 extraction had a crucial role in increasing extraction yield (up to 81.8 ± 1.0 g/kg) and offering possibilities for more selective extractions, particularly of sterols and nonflavonoids (phenolic acids and trans-resveratrol) compared to cold pressing. The highest concentrations of these compounds were extracted with the longer PEF pretreatment followed by the extraction at 35 MPa and 45 °C, amounting up to 5347.0 ± 0.6 mg/kg and 1378 ± 6 mg/kg for sterols and nonflavonoids, respectively.