SUSTAINABLE BIO-BASED EMULSIFIERS FROM WINE LEES VALORIZATION

Wine lees are solid residues formed at the bottom of fermentation vessels during wine production. Although their composition varies depending on grape variety, geographical origin and environmental conditions, wine lees mainly consist of yeast cells, tartaric and phenolic acids, proteins, sugars and residual metabolites [1,2]. This by-product of the agri-food industry represents a valuable source of glycerol, which can be recovered and valorized as a renewable feedstock for the synthesis of monoacylglycerols (MAGs). MAGs are non-ionic surfactants widely used in the pharmaceutical, cosmetic and food industries. Conventional chemical synthesis of MAGs requires acidic or basic catalysts and high temperatures, resulting in a mixture of glycerides that must be separated via high-vacuum distillation, which raises production costs. In contrast, enzymatic approaches represent a sustainable and promising alternative, offering enhanced selectivity, simpler processing, and lower energy consumption during downstream operations [3]. In this study, red and white wine lees were used as raw materials to produce bio-based emulsifiers (Figure 1). Glycerol was recovered from both types of wine lees using different extraction techniques, including standard solid–liquid and Soxhlet extractions. To improve the extraction efficiency, both one-pot and sequential extraction approaches were investigated using solvents of increasing polarity (n-hexane, ethyl acetate, acetone, ethanol, and water) [4]. The main classes of compounds present in the extracts were characterized by spectrophotometric assays (Folin–Ciocalteu, Anthrone, and Bradford methods), whereas glycerol content was quantified by NMR spectroscopy. Extracts enriched in glycerol were subsequently subjected to solvent-free enzymatic esterification using Novozym® 435 as the biocatalyst and palmitic acid as the acyl donor, yielding 1-palmitoylglycerol. The surface-active properties of the synthesized MAGs were studied by measuring their ability to reduce interfacial tension and to stabilize water-in-peanut oil (W/O) emulsions over time.