Dried and milled marc was extracted with the solvent in a thermostatic rotary shaker (Infors AG, CH-4103 Bottmingen/Switzerland) with a 4/1 (v/w) ratio solvent/sample (wet weight of oven dried marc). The liquid extract was separated from solids by centrifugation (5350 g for 5 min, ALC 4237R centrifuge).
In the first phase of experimentation two temperatures (45 C and 60 C) and different maceration times (1–3–5– 7–9–15–20–24 h) with absolute ethanol as solvent were tested. Liquid extracts were analysed for content of total phenols (Folin–Ciocalteu method), tannins and anthocyanins.