Optimization of Protein and Polysaccharides Extraction from Post-Distillation Wine Lees (Vinasse) in View of Future Scale-Up

Annually, vast amounts of winemaking by-products are produced globally, yet these are only partially valorised. Among them, wine lees—a sludge comprising exhausted yeasts collected after wine racking—are significantly underexploited. Often discarded post-distillation, they typically represent a cost for distillers and pose environmental challenges (De Iseppi et al., 2020; Varelas et al., 2016). In response, recent studies have suggested subjecting wine lees to an autoclave-based extraction process to obtain valuable food ingredients such as mannoproteins and β-glucans (De Iseppi et al., 2021a). However, for these strategies to become commercially viable, technological advancements are needed. Specifically, to design a pilot extraction plant integrated with current distillery operations, it is necessary to determine the optimal setup for maximizing the extraction yield and to comprehensively study the physical characteristics of wine lees throughout the process. This study aims to find the optimal setup (temperature/time/solids concentration) for the thermal extraction of yeast proteins and polysaccharides from post-distillation wine lees (vinasse). Furthermore, by evaluating the physical properties of this fluid, the study seeks to recommend the most suitable equipment for scaling up this technique. To achieve this, 15 wine lees samples with differing solid concentrations (10, 30, 50%) were subjected to treatment at different temperatures (104, 108, 112 °C) and durations (20, 40, 60 min) using a pressure cooker device. Samples were then analyzed for total proteins and polysaccharides. The results were compared with those obtained from an autoclave-treated sample prepared using a previously published method (De Iseppi et al., 2021b), as well as with the control (non-heat treated). The statistical analysis revealed that the highest protein extraction occurred at 110°C, with a 30-minute cooking time and a solid particle concentration of 20%. Regarding polysaccharides, optimal extractions for high molecular weight fractions occurred under mild temperature, concentration, and time conditions, while the extraction of the medium molecular weight fraction was favored by longer durations, a solid particle concentration of 30%, and lower temperatures. Viscosity measurements indicated a transition from Newtonian to pseudoplastic behavior between solid concentrations of 30% and 50%. Density and specific heat remained stable across different treatment conditions. Based on these findings, the envisioned industrial plant includes a vertical disk separator for solids concentration, an industrial cooker for extraction, and rotary pumps for fluid transport. In conclusion, this study provides a preliminary analysis for designing a plant to address the significant issue of wine lees valorization after distillation. Considering that optimal extraction conditions vary depending on the targeted fraction, the research underscores the importance of tailored operational conditions for protein and polysaccharide extraction. The implementation of such a design, coupled with a versatile pilot plant, could represent a significant step towards the adoption of circular economy practices within the wine sector.