ANTHOCYANINS EXTRACTION FROM GRAPE POMACE USING EUTECTIC SOLVENTS

Malolactic fermentation (MLF) is a desired process to decrease acidity in wine. This fermentation, carried out mostly by Oenococcus oeni, is sometimes challenging due to the wine stress factors affecting this lactic acid bacterium. Wine is a harsh environment for microbial survival due to the presence of ethanol and the low pH, and with limited nutrients that compromise O. oeni development. This may result in slow or stuck fermentations. After the alcoholic fermentation the nutrients that remain in the medium, mainly released by yeast, can be used in a beneficial way by O. oeni during MLF.

Wine flavanols are extracted from grape skin and seeds along red winemaking. Potentially, eight flavan-3-ol subunits may be present as monomers or as tannins constituents, being these catechin, epicathechin, gallocatechin, epigallocatechin end the gallates of the mentioned units. In this work the flavanol profiles of grape skins and seeds before (grapes) and after (pomace) red winemaking were studied together with the one in the corresponding wines. The trials were made over two vintages in Vitis vinifera cv. Tannat, Syrah and Marselan from Uruguay.

During bottle aging, many thiol compounds are involved in the expression of bouquet of great aged red wines according to the quality of the closure.1,2 Identifying thiol compounds in red wines is a challenging task due several drawbacks including, the complexity of the matrix, the low concentration of these impact compounds and the amount of wine needed.3,4
This work aims to develop a new strategy based on the functionalisation of oak wood organic extracts with H₂S, to produce new thiols, in order to mimic what can happen in red wine during bottle aging. Following this approach and through sensory analysis experiments, we demonstrated that the vanilla-like aroma of fresh oak wood was transformed into intense “meaty” nuances similar to those found in old but non oxidized red wines.

The aging potential of Burgundy chardonnay wines is considered as quality indicator. However, some of them exhibit higher oxidative sensitivity and premature oxidative aging symptoms, which are potentially induced by no-enzymatic oxidation such as Fenton-type reaction (Danilewicz, 2003). This chemical mechanism involves the action of transition metal, native phenolic compounds and oxygen which promote the generation of highly reactive oxygen species (ROS) such as hydroxyl radicals (OH) or 1-hydroxyethyl radicals (1-HER) from oxidation of ethanol. Such mechanism is involved in the radical oxidation occurring during bottle aging. According to Elias et al.,(2009a), the 1-HER is the most abundant radical in forced oxidation treated wines. Consequently, understanding its evolution kinetic in dry white wines is of great importance.

Today, nearly one billion bottles of different sizes and capacities are aging in Champagne cellars while waiting to be put on the market. Among them, several tens of thousands of prestigious cuvees elaborated prior the 2000s are potentially concerned by prolonged aging on lees. However, when it comes to champagne tasting, dissolved CO₂ is a key compound responsible for the very much sought-after effer-vescence in glasses [1]. Yet, the slow decrease of dissolved CO₂ during prolonged aging of the most prestigious cuvees raises the issue of how long a champagne can age before it becomes unable to form CO₂ bubbles during tasting [2].