The combined extraction of polyphenols from grape marc: Ultrasound assisted extraction followed by supercritical CO2 extraction of ultrasound-raffinate

- Ultrasound-extract of grape marc at 80 °C for 4 min was very rich in polyphenols.
- Supercritical carbon dioxide-extract of ultrasound-raffinate depleted polyphenols.
- Combining processes increased polyphenols yield compared to controls.
- Extracts from combined process had stronger antioxidant effect than controls.

A combined process of ultrasound assisted extraction (UAE) and supercritical carbon dioxide (SC-CO2) extraction of the correspondent UAE-Raffinate for the recovery of polyphenols from defatted grape marc was developed on pilot-plant scale. The extraction of polyphenols using UAE at different extraction time (4 and 10 min) and temperature (20 and 80 °C) was investigated. The overall extraction curves of UAE-Raffinates extracted by SC-CO2 described and critically evaluated. The performance of the combined process was checked by total polyphenols yield, proanthocyanidins content and antioxidant activity. Compared to other previous studies, the polyphenols extraction yield obtained by the combined process was significantly enhanced (3493 mg GAE/100 g DM) as well as the antioxidant activity (7503 mg α-tocopherol/100 g DM).