Red grape skins (GS) of Barbera cultivar (Vitis vinifera L.), collected from wineries recovered in the Piedmont region, were sieved (with a 5 mm sieve) to separate the skins from the seeds, dehydrated at 50 °C, and finely milled by a rotor mill (Cross Beater Mill, Retsch GmbH, Germany) at room temperature. The powders thus obtained were sieved (50 g batches; 10 min; amplitude 8) by means of an analytical sieve shaker Octagon Digital (Endecotts Ltd., England), equipped with three certified sieves (openings: 125, 250 and 500 μm). The following GS powders fractions were collected: small (S ≤ 125 μm), medium (125 < M ≤ 250 μm) and large (250 < L ≤ 500 μm). The three GS powders were immediately vacuum packed and stored at 4 °C until further use