Valorization of wine lees for oenological interest by eco-responsible processes

Abstract

Wine lees are the second most important wine by-product in terms of quantity after grape stalk and marc. During aging on lees, it is well known that wine lees yield compounds that act as antioxydant. However the chemical nature of the compounds involved in this behavior (except polyphenols and glutathione) has not yet been totally elucidated. The scarce knowledge of wine lees composition and their potential exploitation make them a promising candidate to obtain new antioxidant products to be used in winemaking. In this study, an eco-sustainable approach to obtain lees extracts exhibiting antioxidant capacity is proposed. Such extracts could be used in a global enological strategy of sulfites level reduction.

During this work, lees extraction has been carried out with conventional solvent and subcritical water extraction. The solid/liquid ratio and the influence of extraction duration were studied for each solvent. The total composition of lees extracts was assessed. Proteins, lipids, polysaccharides, polyphenols, and glutathione analyses were performed by spectrophotometry and HPLC. Antioxidant capacity of each extracts was evaluated by three methods: the ability of antioxidants to scavenge a radical by DPPH, ferric reducing antioxidant power by FRAP and Oxygen Consumption rate (OCR) by direct oxygen consumption measurement.
Results show an important effect of operational conditions, solvent and matrice on the diversity of extracts in terms of composition and bioactivity. For the first time, an eco-sustainable process has been proposed for the valorization of white wine lees to obtain extracts with high antioxidant activity. The extracts antioxidant capacity is promising to their target application in vinification as well as in food industry in order to reduce doses of sulfites.