Sensory impacts of the obturator used for the Chasselas: study over the time

Winemaking decisions and techniques are known to affect the final aromatic composition of red wines. Winemakers put a constant effort into the improved controlling of vinification procedures to achieve better quality. Anyway an increased customer’s demand for uniqueness is often forcing them to adjust and offer new and new interesting products. To support the producers, an improved knowledge on aromatic potential as affected by classical and alternative strategies is needed.

Must oxidation is a complex process involving multiple enzymatic transformations, including the oxidation of phenolics containing an ortho-diphenol function. The latter process has a primary influence on wine aroma characteristics and stability, due to the central role of ortho-diphenols in the non-enzymatic oxidative reactions taking place during winemaking and in finished wine. Although oxidation of must is traditionally avoided, in recent years its contribution to wine quality has been revisited, and in some cases improvements to wine aroma have been observed with the application of controlled must oxidation. Nowadays there is a great interest in the wine industry towards the identification of specific markers or patterns to characterize and classify the response of grape must to oxidation.

From the standpoint of wine aroma oxidation there are two effects observed: aroma degradation of oxygen sensitive compounds (polyfunctional mercaptans) and the appearance of new substances with high aromatic power (acetaldehyde, methional, phenylacetaldehyde, sotolon, alkenals, isobutanal and 2, 3-metylbutanals) (1-5). According to our experience, Strecker aldehydes are compounds with highest sensory relevance in the oxidative degradation of many wines (5-7).

The aromas found in young Bordeaux red wines made with Merlot and Cabernet Sauvignon suggest a complex mixture of aromas of fresh red fruits such as cherry or blackberry for Merlot, and strawberry or blackcurrant for Cabernet Sauvignon. The aromas of these wines are closely linked with the maturity of the grapes. The climate change that has occurred during the last decade in Bordeaux has induced changes in the ripening conditions of grape berries. It is now widely admitted that over-ripening of the berries during hot and dry summers results in the development of characteristic flavors reminiscent of cooked fruits (fig, prune). The presence of these overriding odors found in both musts and young wines affects the quality and subtlety of the wine flavor and may shorten its shelf life.

Phenolic compounds are important quality indicators in red wine. A large number of polyphenols play an important role in wine development, contributing to the colour and the sensory perception of the wines. Anthocyanins are the pigments responsible for the colour in young red wines while tannins are the principal contributors to the bitterness and the astringency of the wines. Wine polyphenols are considered more complex molecules than grape phenolics, due to the enormous number of chemical reactions which take place during the entire winemaking process and storage, forming more stable compounds.