High-pressure fractionation of spent coffee grounds oil using green solvents

Abstract

Coffee industry generates large amounts of organic waste, including residues obtained during instant coffee production, referred to as spent coffee grounds (SCG). In this work, methods for extraction and fractionation of oil from SCG, focusing on the phenolic compounds content (TPC), were investigated at 333 K and 40 MPa, in one or two steps, with different solvents: pure supercritical CO2 (scCO2), ethanol and supercritical mixture of CO2 with ethanol (90:10 w/w). Fractionation was also evaluated in four separators aligned in series at 323 K at different pressures and ethanol concentrations. The ethanolic extract (E) presented the highest overall yield (25 wt%). Samples from the first separator obtained during fractionation of ethanolic extract showed TPC values up to four times higher than the original extract. Similar TPC enrichment was observed via two-step extraction. The results indicated the methods proposed are efficient to obtain extracts from SCG with higher content of phenolics.