White wine lees protein extract: A promising fining agent for red wine clarification

This study investigates the potential of white wine lees, a protein- and polysaccharide-rich winemaking by-product, as a sustainable fining agent for red wine clarification. Protein-rich extracts were produced using subcritical water extraction (SWE) and optimized via Response Surface Methodology. Chemical and molecular analyses (SDS-PAGE and SEC) revealed that the extracts were enriched in low to medium-molecular-weight peptides, similar to commercial gelatin hydrolysates. The fining performance of the extract was assessed in red wine and compared to commercial products like whole lees, gelatin, and patatin. The lees extract significantly reduced turbidity (−64.4 %) and tannin content (−18.4 %) while preserving color stability, achieving performance comparable to gelatin and superior to patatin. Moreover, it effectively reduced wine astringency, with minimal impact on chromatic characteristics. These findings demonstrate that SWE-derived white wine lees extract is a promising alternative to conventional fining agents, supporting circular economy practices in the winemaking industry. • Subcritical water extraction produces protein-rich fractions. • Extracts exhibit fining properties comparable to conventional agents (e.g., gelatin). • Lees-derived extracts effectively reduce turbidity and tannins of wine while preserving color. • Sustainable, wine-based fining alternative supporting the circular economy.