Leaf Removal and Wine Composition of Vitis vinifera L. cv. Nero d’Avola. The volatile aroma constituents.

BACKGROUND: Defoliation is a cultural practice for crop management in grapevines and the benefits effects have been demonstrated. Here, the influence of “early” leaf removal on the quality of Nero d’Avola wines was evaluated. Particular attention has been given to the volatile constituents responsible for the wine aroma but also to the total amount of polyphenolic compounds, anthocyanins and flavonoids. RESULTS: “Early” defoliation was manually applied and compared with non-defoliated controls. The grapes were harvested in two different ripening times following their technological and phenolic maturity. Statistical quantitative differences resulted among the samples from the four theses. Both the time of harvest and the vine leaf removal determined variation in the wine composition. A large number of volatile constituents were identified and quantified; the OAV were calculated. Basal leaf removal reduced pH and increased titratable acidity, total amount of anthocyanins, flavonoids, polyphenols and color intensity in the wines from the 1st harvest. Interesting resulted the increase for fermentation and varietal aromas in the defoliated wines from the 1st harvest. Limited differences resulted between the wines from defoliated and control vines relative to the 2nd harvest. PCA which was applied to the compounds with an OAVs ≥ 0.5 allowed to distinguish the different theses. CONCLUSION: “Early” leaf removal can lead to a positive effect on the quality of Nero d’Avola under the environmental conditions in which the present study was realized but particular attention has to be given to the time of grape harvest.The results also demonstrate that “early” defoliation can be applied to improve the wine quality also in Mediterranean area with a concentration of rainfall during winter, nearly aridity and high temperature in summer season.