Testing novel non-thermal treatments for the extraction of valuable fractions from wine lees

Wine lees, a significant by-product of vinification, are rich in high-value compounds such as yeast polysaccharides, proteins, and grape polyphenols. Despite their potential, these materials are poorly valorized except for the ethanol distillation. This study investigates sustainable and novel non-thermal extraction technologies for the valorization of wine lees. Different wine lees samples collected before and after distillation were subjected to various treatments, including high-pressure processing (at 700 and 1000 bar) and sonication (probe and bath) with/without enzymatic pre-treatment with commercial beta-glucanase enzymes. The objective was to assess the efficiency of these methods in extracting valuable compounds (polysaccharides, proteins, polyphenols), thus indicating the most suitable approach Polysaccharide concentration and molecular size distribution were evaluated using HPLC-SEC-RID, protein levels were measured via the BCA assay, and polyphenolic profile was analyzed using RP-HPLC-DAD at 280 and 310 nm. Results showed that high-pressure treatment at 1000 bar was the most effective in extracting high-molecular-weight polysaccharides, while sonication with probe yielded significant amounts of low-molecular-weight saccharides. These approaches also resulted in the highest protein recovery among all tested methods. Sonication combined with enzymatic pre-treatment also showed promising results, particularly for pre-distillation wine lees. Additionally, total polyphenol release was quantified across all treatments, and gallic acid was identified as a commonly detected compound. These results suggest that method selection should be based on target compound characteristics and processing goals. High-pressure and ultrasonication techniques offer promising alternatives for the recovery of valuable compounds from wine lees, contributing to sustainable food production and circular economy practices.