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 at two different ripening times following their technological and phenolic maturity. Statistical quantitative differences occurred among the samples from the four trials (defoliated and control samples, both at two ripening times). 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 odour activity values (OAVs) were calculated. Basal leaf removal reduced pH and increased titratable acidity, total amount of anthocyanins, flavonoids, polyphenols and colour intensity in the wines from the first harvest. Results showed the increase of fermentation and varietal aromas in the defoliated wines from the first harvest. Limited differences occurred between the wines from defoliated and control vines relative to the second harvest. Principal components analysis, which was applied to compounds with OAVs ≥ 0.5, allowed the different compounds to be distinguished. 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 undertaken 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 wine quality in the Mediterranean region, where there is a concentration of rainfall during winter, and nearly arid conditions and high temperatures during the summer.

Varietal Aromas of Fortified Wines from Different Moscato Var. (Vitis vinifera L.) under the Same Pedoclimatic Conditions.

Vitis vinifera L. cv. Moscato includes different varieties mainly used to produce sweet wines, such as fortified wines. Moscato grapes are characterized by a large number of free and glycosylated monoterpenoids giving very aromatic wines. However, the literature data on the aroma profile of fortified Moscato wines are very limited. In light of this, the present research aimed to investigate the aroma compounds, mainly the varietal ones, of fortified wines from different Moscato varieties, namely Giallo (Yellow), Bianco (White), Bianco at Petit Grain (Blanc à Petits Grains), Ottonel and Rosa (Pink of Trentino), cultivated under the same pedoclimatic conditions. Using the HS-SPME-GC-MS (head space-solid phase micro extraction-gas chromatography-mass spectrometry) technique, numerous varietal and fermentative aroma compounds have been identified and quantified and significant differences were observed among varieties in the levels of mostly volatiles and in their ratios. Based on their composition, the studied wines can be divided in two groups depending on whether linalool or geraniol prevails among varietal aromas. These results are evidence that each Moscato variety has a typical varietal aroma composition, even if some similarities were found between the two white varieties, and between Moscato Giallo and Moscato Ottonel varieties. Moscato Rosa showed a peculiar aroma composition and the lowest ester/terpene ratio.