Characterisation of polyphenols and antioxidant potential of red and white pomace by-product extracts using subcritical water extraction

A detailed assessment of the content of high added-value compounds in grape pomace varieties was carried out following a subcritical water extraction method. High amounts of anthocyanins and tannins were recovered from fermented grape pomace at differential temperatures with high variability between the by-products observed. Contrary to anthocyanins, high extraction temperatures (about 200 °C) yielded higher amounts of tannins. Overall, we found that grape pomace antioxidant activity and total polyphenols, quantified by the Folin Ciocalteu method, were not directly related to the main polyphenol content in SWE extracts. The data obtained in our study by using laboratory-scale equipment will be useful for developing an industrial-scale SWE process. Finally, it was shown that grape pomace by-products can be considered asan important source of polyphenols. They could therefore potentially provide a basis for the sustainable and integrated exploitation of winemaking by-products, to be used as inexpensive and readily available sources of bioactive compounds for the pharmaceutical, cosmetic and food industries.