Mannoproteins extracts from wine lees: characterisation and impact on wine properties

This study aims at exploiting an undervalued winemaking by-product, wine yeast lees, by developing efficient and food-grade methods for the extraction of yeast glycoproteins. These extracts were then supplemented to wine and their impact on wine properties assessed. White wine lees were produced by fermenting Sauvignon blanc grape juice with S. cerevisiae Uvaferm HPS strain. Three extraction methods were applied on lees using physical (autoclave and sonication) or enzymatic (Glucanex®, an industrial β-glucanases) approaches. Glycoproteins extracts were characterized by SEC-HPLC and SDS-PAGE. After their addition to wine (0.5 g/L), no alteration of wine clarity was detected. The ultrasonication and enzymatic extracts, containing a relatively low amount of glycoproteins, led to a significant decrease in wine protein haze formation upon heat test (-7%). Conversely, the autoclave extract was the richest in glycoproteins and had a positive impact on wine foaming properties, inducing an increase in foam’s maximum height and stability which were 2.6 and 3.6 times higher compared to a model wine. The autoclave extract improved tartrate stability as shown by a decrease in wine conductance (-11%) compared to the untreated wine. Results suggest that white wine lees could be considered a valuable source of glycosylated proteins with potential applications in winemaking. In this context, the autoclave appears as the more promising method in terms of both efficiency and extract’s effectiveness. The proposed food-grade exploitation approach could represent an important tool to improve the environmental and economical sustainability of the wine supply chain.