Extraction of antioxidants from winery wastes using subcritical water

Subcritical water extraction of phenolic compounds from grape pomace was performed. The combined effects of extraction temperature (100, 120 and 140 °C) and pressure (8 MPa, 11.5 MPa and 15 MPa) were investigated using a 32 full factorial design and response surface methodology. Extractions with significantly higher polyphenols, flavonoids and antioxidant activity were achieved when using subcritical water extraction compared to conventional methods. The optimum extraction conditions and the desirability of model were at 140 °C and 11.6 MPa (0.9550). At this operating condition, 31.69 mgGAE/gDP and 15.28 mgCE/gDP of total polyphenols and flavonoids were recovered, respectively. The extracts showed antiradical power of 13.40 μgDPPH/μlextract. Subcritical water extraction was more efficient than using water and ethanol at atmospheric pressure for the extraction of these compounds.

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► Subcritical water extraction of phenolic compounds from grape pomace was performed.
► The effects of pressure and temperature on phenolics extraction were evaluated.
► Higher contents of polyphenols, flavonoids and antioxidant activity were achieved.
► Subcritical water extraction was more efficient than conventional aqueous system.