Spectrophotometric detection of changes in phenol content of red berry skins during grape ripening

Spectrophotometric detection was performed in order to characterize and to quantify phenolic compounds, Hydroxycinnamic Tartaric Acids (HCTAs), Flavonols and Anthocyanins, in berry skin of four different red Vitis vinifera L. varieties, (Alicante, Black Malvasia, Nerello and Prunesta), cultivated in the Reggio Calabria province (South Italy). Five samplings were conducted during ripening, at weekly intervals. The evolution of these phenolic fraction has been monitored by separating the phenols into different classes by SPE. The adsorbing resin Serdolit XAD-2 was employed. This approach provided good performance in terms of linearity, accuracy and precision. Grape skin showed to be rich in phenolic components and especially in anthocyanins whose content increased during ripening, being maximum at commercial ripeness of grapefruit.