SUB-CRITICAL WATER: AN ORIGINAL PROCESS TO EXTRACT ANTIOXIDANTS COMPOUNDS OF WINE LEES
Wine lees are quantitatively the second most important wine by-product after grape stems and marc . In order to recycle, distilleries recovered ethanol and tartaric acid contained in wine lees but yeast biomass is often unused. It has already been demonstrated that this yeast biomass could be upcycled to produce yeast extracts of interest for wine chemical stabilization . In addition, it is well known that lees, during aging, release compounds that preserve wine from oxidation. Currently, very few studies have focused on the characterization and valorisation of the antioxidant component of lees. Although the role of glutathione has been demonstrated , recent studies have shown that S- and N- containing compounds are the main contributors to the antioxidant metabolome of wine . Thus, the valorisation of wine lees to obtain compounds with antioxidant capacity seems to be of great interest for the wine industry.
In order to obtain extracts with antioxidant properties from white wine lees, we studied the interest of subcritical water as a green extraction process. The extraction conditions (temperature, extraction duration and stirring speed) were optimized by Response Surface Methodology (RSM) to maximize the antioxidant properties of the obtained extracts. The composition of the soluble fraction such as total phenolic content, protein, SH- compounds and glutathione was determined by spectrophotometry and LC-MS methods. Global antioxidant activity of extracts was determined by DPPH (radical-scavenging power), FRAP (Ferric reducing antioxidant potential) and OCR (Oxygen Consumption Rate) in model wine solution.
Results show that temperature is the key parameter for obtaining extracts with high antioxidant activity. Interestingly, we observe that the antioxidant potential does not seem to be related to the presence of a single molecule but rather to the presence of a pool of reducing compounds.
To conclude, subcritical water is a promising eco-sustainable process to obtain antioxidant compounds from wine lees. Such extracts could be used for a targeted application in oenology as well as in other sectors (food, cosmetics, pharmaceuticals).
Issue: OENO Macrowine 2023
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Wine lees, antioxidant, subcritical water, response surface methodology