Extraction of anthocyanins from grape skins assisted by high hydrostatic pressure

The effect of different parameters such as high hydrostatic pressure (HHP) (200, 400, 600 MPa), ethanol concentration (20–100%), time (30–90 min) and temperature (20–70 °C) was studied for the optimal anthocyanin extraction from red grape skins. Extracts obtained at an ethanol concentration of 50%, at 70 °C and 600 MPa possessed the highest antioxidant capacity (μmol TROLOX equivalents(TE)gDM-1) and the extraction yields were three-fold greater than control extractions. The antioxidant capacity of the extracts was not directly correlated to the highest amount of anthocyanins, which were optimal extracted with the set of conditions – 100% ethanol, 50 °C and 600 MPa – achieving extraction yields about 23% higher than under control conditions. Anthocyanin recovery under HHP was selective and increased according to the glucoside moiety linked to the flavylium nucleus; p-coumaroylglucoside anthocyanins were more favourably extracted than mono- and acetylglucosides. Therefore, a higher extraction rate was related to the higher number of methoxyl and hydroxyl groups linked to the C3 and C5 of the flavylium nucleus, hence extraction of malvidin > peonidin > petunidin > delphinidin > cyanidin.