2.2.1. trans-Resveratrol analysis
The grape skin, pulp, and seeds from 40 berries were extracted
with a ternary system of ethanol:water:aqueous solution of 0.12 M
hydrochloric acid (70:29:1 v/v/v) for 4 h, according to Iacopini, Baldi,
Storchi, and Sebastiani (2008). The extracts were centrifuged for
10 min at 2500×g. The precipitate was extracted again with the same
solvent and made up to a final volume of 200 mL for skin and pulp and
100 mL for seeds.