Spent coffee grounds-derived water-in-oil-in-water double emulsions for edible coffee oil aroma preservation: A sustainable approach

Spent coffee grounds (SCG) are generated in large quantities by the coffee industry and contain underutilized biomolecules with potential for sustainable food applications. This study focused on the development of water-in-oil-in-water (W/O/W) double emulsions, using SCG-derived polysaccharide-rich extracts to protect spent coffee oil (SCO) from oxidation and preserve its aroma. SCO was recovered by Soxhlet extraction (n-hexane and ethanol), while microwave-assisted extraction of defatted SCG yielded MW1_Sn and MW2_Sn, obtained at 150 °C and 180 °C, respectively. Ethanol-recovered SCO exhibited higher phenolic content and antioxidant activity, and both MW extracts displayed similar galactomannan/arabinogalactan-rich profiles, with MW1_Sn containing higher levels of chlorogenic acids. The resulting emulsions exhibited stable droplet morphology, particularly those formulated with MW1_Sn and surfactants, and preserved desirable aroma compounds, like furans, while limiting the release of lipid-oxidation markers, as aldehydes. These results demonstrate the feasibility of repurposing SCG into sustainable food-grade emulsions capable of protecting edible coffee oil aroma.