Evolution of some phenolic components, carotenoids and chlorophylls during ripening of three Italian grape varieties

A typical Italian white grape cultivar (Erbaluce) and two red ones (Barbera and Nebbiolo), all grown in the same vineyard, were picked at various ripening stages, from differentiation of the berry to the harvest, and analysed by HPLC to determine carotenoids, chlorophylls and polyphenols, i.e. the major antioxidant components. With regard to carotenoids, mostly represented by β-carotene and lutein, similar initial concentrations were found in the three cultivars. After an initial increase, carotenoids content decreased in the three cultivars, followed in the red grapes by a new peak, mainly due to lutein. Chlorophylls decreased in all cultivars and they almost disappeared in the white grapes, while 14-20% of the initial concentration was found in the red ripe grapes. Total phenolics showed a progressive increase up to veraison, then a decrease occurred, which was counteracted in red grapes by the formation of anthocyanins. The evolution of catechins (as the sum of (+)catechin and (-)epicatechin) and flavonols (as the sum of rutin, quercetin and quercetin-3-glucoside) was similar in all grapes: initial concentration was low (about 1 mg/100 g dw), a peak corresponding to veraison was observed, then a rapid decline occurred to final concentrations between 10 and 20 mg/100 g dw. Climatic conditions and sun exposure seem to play an important role in the evolution of the components under investigation, since very similar profiles were observed in the three cultivars.