Coffee Pulp Valorization Strategy: Flavonoid- and lipid-enriched food-grade ingredients obtained from an advanced extraction technology

The valorization of coffee pulp (CP) is gaining interest because of its content in high-value bioactive compounds. Flavonoids and lipids have been traditionally recovered from coffee by-products using organic solvents such as methanol, hexane, or acetone. However, the toxicity of these solvents limits their food applications. Accordingly, the development of food-grade extraction processes is promoted, supporting the idea of sustainability. This work investigated the feasibility of ethanol-modified supercritical carbon dioxide (EtOH-scCO₂) extraction as a safe and green technique for recovering flavonoids and lipids from CP. The extraction conditions, namely, temperature (45, 55, and 65 °C), pressure (20 and 30 MPa), and EtOH proportion (5 and 10%), were screened using response surface methodology for maximizing the selectivity and efficiency of lipid and flavonoid recovery. The results revealed that EtOH proportion significantly increased (p < 0.05) the extraction efficiency but decreased (p < 0.05) the extraction selectivity of flavonoids and lipids. Compared to conventional aqueous and ethanolic solid–liquid extractions, EtOH-scCO₂ yielded lower flavonoid recovery efficiency, while the opposite was observed for lipids compared to ethanol extractions. However, a superior extraction selectivity was achieved using such advanced technology compared to conventional extractions, namely, up to 33.7 mg CE/g extract for flavonoids at 45 °C, 30 MPa, and 5% ethanol; and 505 mg /g of extract for lipids at 55 °C, 30 MPa and 5% ethanol. Overall, these results revealed that the EtOH-modified sc-CO₂ extraction technology from CP could be a promising approach for obtaining flavonoid- and lipid-enriched food-grade ingredients. Hence, this research contributes to the circular bioeconomy paradigm framed on the valorization of agri-food by-products.