Sustainable strategies for the management and valorization of wine lees

Abstract

Wine lees represent an abundant yet largely undervalorised by-product of the winemaking industry. In particular, lees rich in spent yeast biomass, collected after racking or distillation, hold considerable potential for the extraction of bioactive macromolecules such as mannoproteins and polysaccharides with relevant food and technological applications. However, several limitations hinder their industrial valorization, including low extraction yields, high processing costs, and the lack of processes that are compatible with current distillation practices. This presentation outlines two complementary strategies aimed at overcoming these obstacles by focusing on sustainable approaches for the extraction and valorization of post-fermentation and post-distillation wine lees. The first strategy explores, for the first time, the combined use of natural deep eutectic solvents (NADES) and autoclave treatment (121°C, 20 min) to enhance yeast cell wall solubilization. Three food-grade NADES were tested for their physicochemical stability and extraction performance. Results showed high extraction yields for both polysaccharides (up to 33.2 g/100g) and proteins (up to 6.6 g/100g), with promising functional properties such as emulsifying activity (56–62%), high viscosity (>70 Pa·s), and good foaming ability at wine pH (3.4). The solvents remained stable under thermal treatment, supporting their use in green extraction processes. The second strategy focuses on optimizing thermal extraction conditions for a scalable process using post-distillation lees, with the goal of designing a pilot plant that can be integrated into existing distilleries. To this end, Response Surface Methodology was applied to assess the combined effects of temperature (104–112°C), time (20–60 min), and solids concentration (10–50%) through 15 treatment combinations using a pressure extraction system. Results indicated optimal protein extraction at 110°C, 30 min, and 20% solids, while varying conditions favored different polysaccharide fractions. The physical characterization of the extracts (viscosity, density, specific heat) informed the selection of suitable equipment, including vertical disk separators, industrial cookers, and rotary pumps. Overall, these studies present two complementary and sustainable strategies to convert wine lees into valuable functional ingredients, offering a concrete step towards the adoption of circular economy practices in the wine sector.