Valorization of winemaking by-products through circular economy approaches

Abstract

Winemaking generates significant amounts of by-products, such as grape pomace and wine lees, which are primarily used for distillation and composting. However, these by-products are rich in valuable compounds like oils, proteins, polysaccharides, and polyphenols that remain largely underutilized. This study aims to minimize the environmental footprint of the wine industry by adopting a circular economy approach, focusing on the extraction and reuse of active compounds in various winemaking stages, ranging from biocontrol in vineyards to oxidative stabilization of wine.

An environmentally friendly and selective extraction method, supercritical fluid extraction (SC-CO₂), was employed to recover high-value molecules. Using SC-CO2 alone, oil extraction from grape pomace and seeds yielded 7% and 12% w/w, respectively, with 69% unsaturated fatty acids. These fatty acids were preserved due to the extraction temperature (40°C). Additionally, polyphenols were coextracted, serving as antioxidants that contribute to the stabilisation of the extracted oil. SC-CO₂ with water as a co-solvent also enabled the isolation of water-soluble compounds, including low-methoxy pectin (400 kDa), 9% proteins, and polyphenols. The total yield of water-soluble polyphenols reached approximately 200 mg/100 g gallic acid equivalent (GAE), including catechin and epicatechin [1]. Moreover, this green extraction method preserved the native structure of the extracted protein as demonstrated by calorimetry measurements.

To enhance the selectivity of compound recovery, functionalized mesoporous silica-based materials (MMS-f) with tailored functional groups such as hydroxyl (OH), thiol (SH), or amine (NH₂) were tested. These materials proved highly effective and versatile for adsorbing specific compounds, such as small peptides (e.g., glutathione) and proteins (e.g., beta-lactoglobulin as a model of globular proteins) [2, 3]. Their primary function is to isolate and concentrate the targeted molecules, releasing them in a minimal volume of water through desorption. This concentrated solution can then be dried to preserve the active molecules, thereby optimizing the drying process. This work aligns with several Sustainable Development Goals, particularly SDG 12, SDG 7 and SDG 13.