Effect of ozone application for low-input postharvest dehydration of wine grapes 

The color of a red wine is one of the most important parameters of its quality, giving much information on its status, such as the grape variety used or the winemaking style. As the result of a complex equilibrium between different forms of anthocyanins and polymerization reactions which occur over the course of time, color can also serve as an indication of a wines’ age. For this purpose the “chemical age” i and ii indexes have been introduced by Somers in 1977. The chemical age index i measures the color absorbance after the addition of acetaldehyde while chemical index ii provides an indication of how much of the total red pigments are resistant to SO2 bleaching.

Marselan wines have an unusual high proportion of seed derived tannins from grapes having high proportions of skins, which are rich in tannins. But the causes behind this characteristic have not yet been identified. In vintage 2023 wines were made at experimental scale (9 kg by experimental unit) from Arinarnoa, Marselan and Tannat Vitis vinifera grape cultivars by traditional maceration, and by techniques aimed to increase the wine content in skin derived tannin: addition of extraction enzymes, addition at vatting of grape-skin enological tannins, or by extended maceration, known to increase the seed derived tannin contents of wines. Macerations were of 7 days, except in the extended macerations that were of 15 days.

Ellagitannins are the main oak wood phenolic compounds that contribute to wine and spirits organoleptic quality (color, astringency, bitterness)(1-3). Given the lack of knowledge regarding their composition and evolution in spirits, the objectives were to follow their extraction kinetic in Cognac “eaux-de-vie” matured in barrel representing different toasting and to observe their evolution and structural modifications during aging. METHODS: Eight different toasting levels were used for studying the impact of the toasting on ellagitannins composition. Two verticals (1978-2018) of “eaux-de-vie” samples coming from two terroirs were analyzed in order to observe ellagitannins evolution during aging. The above analyses were conducted using HPLC-Triple Quadrupole mass spectrometer (4) and the unknown compounds were identified by UPLC-Q-TOF, purified by preparative HPLC prior to 1D/2D-NMR analysis.

Varietal flavor is commonly known as the aromatic character of a wine in which the aroma of a particular grape variety predominates. However, not all varieties present particularly pronounced aromas. Therefore, different methods are constantly sought to enhance the aroma of wines with neutral aromatic characteristics, such as the use of glycosidases (1), certain yeast strains (2) or maceration with different agricultural products. In this work, aiming to improve the sensory profile together with the diversification of this product, white wines, derived from a neutral grape variety, were elaborated with the addition of mango peel by-products.

Volatile organic compounds (VOCs) are very important for the characterisation and quality of the final white wine. An oenological practice to increase the extraction of aroma compounds is the cold pre-fermentative maceration [1,2], although it may also release phenolic compounds that confer darker chromatic traits to white wines, not appreciated by consumers. This practice could be improved by the use of enzymes in order to facilitate the release of the odorous molecules. In this study, the effect of different enzyme treatments during skin contact on the chromatic characteristics and volatile composition of white musts from four winegrape varieties was evaluated.