Berry skin thickness as main texture parameter to predict anthocyanin extractability in winegrapes

Red grapes are the only source of anthocyanins in wines and therefore the assessment of their extractability is important for wine quality. To date, a mathematical equation relating skin mechanical properties and anthocyanin extractability has never been performed for different ripening stages and vineyards located in a given production area. The main aim of this work was to assess anthocyanin extractability attempting to its relation with skin textural parameters. Morphological parameters, skin texture characteristics, total anthocyanin contents and extractability percentages were determined in Mencía grape berries (Vitis vinifera L.) from several vineyards and calibrated according to their density at three amounts of soluble solids. Skin mechanical properties were measured by Texture Analysis; a rapid and low-cost analytical technique. In most vineyards, an increasing tendency of texture parameter values was observed with the ripening stage but the differences were not statistically significant. The accumulation of anthocyanins in berry skin usually increased with the ripening stage. Anthocyanin extractability was no influenced by ripening stages for each vineyard studied. The study allowed to establish a skin texture parameter as predictor of anthocyanin extractability for a given production area. Thinner skins seem to be characterized by a greater release of red pigments.