Valorization of wine lees by a sustainable process for enological applications – ValoLi

Wine production is one of the most important agricultural sectors with a production capacity of around 260 million hectoliters. Winemaking process includes numerous steps: the cultivation of thevine, the harvest, the fermentation and the maturation of the wine, but also the management of the generated solid and liquid wastes. Wine production leads to abundant and various wastes, such as grape stalk, grape marc and wine lees. More specifically, wine lees, defined as “the residue accumulating in vinification tank after wine fermentation, represent between 2 and 6 % of wine production. Although their compositions are variables, depending on the winemaking itinerary, the wine lees are mainly composed of ethanol, tartaric acid, inorganic matter, yeast and bacteria. Lees obtained throughout red wine production are known to contain higher levels of polyphenols than those obtained by white winemaking. Accordingly, most of the research studies concern the valorization of polyphenols from red wine lees, with biological or antioxidant effects for applications in food and/or pharmaceutical industries. However, only few studies concern the extraction of antioxidants from wine lees and consider applications as preservatives against oxidation phenomena for wines themselves. Actually, the most widely used preservative in wine industry is sulfur dioxide (SO2). Even if its antioxidant and antimicrobial properties make it essential to preserve quality of wines, proof of associated human hazards led to increasing interests for alternatives development. However, finding substances as much efficient as SO2 remains a challenge, especially regarding its antioxidants properties.
In this context, ValoLi project proposes the valorization of lees from winemaking. The aim of the study is to produce compounds with antioxidant capacity for oenological applications, thereby implementing new sustainable processes. The project concerns multidisciplinary approaches:
1. the development of organic solvent-free processes, including subcritical water extraction and purification by membrane technologies;
2. the chemical characterization of the obtained products, in relation with their ability to protect wine against chemical and/or enzymatic oxidation;
3. the development of specific winemaking protocols in which the use of purified extracts will allow to reduce, or even eliminate, the addition of sulfites, without compromising wine quality.
The innovative nature of the project is related to its integrated approach: from sustainable production of valuable molecules from wine waste to their subsequent use in the wine industry. With the ambition to produce antioxidant alternatives as wine bio-additives extracted from wine waste itself, this project aims to reduce SO2 doses in wine, which represents one of the biggest actual challenges of modern oenology, and food industry in general. In addition, the development and optimization of green processes meets current socio-environmental industrial requirements, such as implementing eco-sustainable production strategies for exhaustive use of raw matter biomass.