Cascade extractions of coffee silverskin: Towards zero solid waste valorization of a byproduct

In a former study it was shown that extracting cycles of coffee silverskin using the previous water extract as solvent with fresh material, results in a caffeine-rich aqueous extract and insoluble fibers. In the present work, we observed that: (1) the concentration in sugar, electrolytes, chlorogenic, ferulic, caffeic acid and antioxidant power increases in the water fraction during the extraction cycles. As a remarkable result the ratios of caffeine to sugar, polyphenols and antioxidant power remains also constant; (2) lignin- and cellulose-rich insoluble fibers can be solubilized using successively the green solvents gamma-valerolactone and N-methylmorpholine N-oxide. Using cascade extractions, it is possible to separate and recover all constituents of coffee silverskin as solid substances as well as liquid fractions, making it possible to leave no solid waste behind. • Zero-waste valorization of the coffee silverskin. • Cascade extractions using water, then Gamma-Valerolactone and N-Methylmorpholine N-oxide. • Cycle extractions, characterization of the co-extracted compounds of interest. • The soluble compounds followed the same behavior than caffeine. • The cellulose, hemicellulose, and lignin contained in the solid phase were separated and dissolved using green solvents.