Circular valorization of coffee silverskin through supercritical CO2 for the production of functional extracts

The development of sustainable procedures for the valorization of industrial biomass waste represents a major challenge for the scientific community. Among the residual biomasses, coffee silverskin could represent an attractive source of bioactive compounds. In spite of its promising applications, silverskin is still underutilized and nowadays is still discarded by roasters as solid waste in landfill. This work presents the application of a green unconventional extraction strategy, supercritical CO2, with a particular focus on the extractability of polar compounds from green coffee beans and their related wasted biomass, coffee silverskin, by means of the addition of ethanol as a co-solvent, allowing us to shift the window of extractables towards more polar molecules. The results point out the ability of the supercritical fluid to efficiently target chlorogenic acids, minimizing the excessive use of organic solvents and avoiding the presence of inorganic or organic acids. The use of a co-solvent, at the expense of reducing the selectivity towards target species, was demonstrated to efficiently co-extract other classes of compounds directly connected to the relevance of silverskin's phytochemical profile, dealing mainly with its antioxidant and prebiotic properties, pointing at interesting applications in functional food products.