Total proanthocyanidins were estimated according to Chira, Jourdes, & Teissedre (2011). This method is based on the Bate–Smith reaction, in which the proanthocyanidins in acid medium release anthocyanidins by heating. The wines were diluted to 1:50 in a 10% ethanol solution. One milliliter of the samples was added to 0.5 mL of water and 1.5 mL of 12 M HCl and the mixture was homogenized. Two tubes for each sample were prepared: one was heated for 30 min in boiled water (sample A), while the other one was maintained at room temperature (sample B). To each tube, 0.25 mL of 95% ethanol was added. The absorbance at 550 nm was then read through a 10 mm optical path. Total proanthocyanidins (g/L) were calculated as 19.33 × (abs550 nmA − abs550 nmB).