The Role of Different Cultural Practices on Polyphenols Evolution During Ripening and on Wine Taste in Black and White Vitis Vinifera Varieties Under Global Warming Scenario.

Abstract

The researches carried out during the PhD were focused on the effects of different cultural techniques on the phenolic compound of Vitis vinifera L., under the ongoing climate change scenario that has been causing negative effects on grape composition and sensory attributes of wines. In the first trial was evaluated the effectiveness of the delayed winter spur pruning after budburst to slow down sugar accumulation in cv. Merlot, with the aim to reduce the decoupling between technological and phenolic maturity. This technique, if applied in a particular period, resulted able to slow down sugar accumulation without negative effects on berry flavonoids and with acceptable loss of yield. Since the topic of the phenolic maturity became important in the evaluation of the effects that global warming and cultural techniques have on black berry varieties, in the second experiment were investigated the changes that occurs on berry flavonoids and in the properties of skin cell wall material during the last part of ripening in cv. Merlot. Total and extractable anthocyanins increased until harvest, as well as the affinity of cell wall material for the commercial seed tannin. This latter aspect might be correlated to the decrease of astringency during ripening. In the third experiment was investigated the role that sunlight incidence on clusters of cv. Grechetto gentile plays on grape composition and on the phenolic tastes of the resulting wines. Increased light incidence determined higher concentration of flavonols in grape and wine and that was correlated to the greater perception of astringency and bitterness of the wines. The set of results of the present PhD enhanced the knowledge on the behavior of grape flavonoids under the current global warming scenario and proposed innovative approaches in the study of the phenolic maturity.