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Coffee Pulp Valorization Strategy: Flavonoid- and lipid-enriched food-grade ingredients obtained from an advanced extraction technology
* 1, 2 , 1, 2 , 1, 2 , 1, 3 , 1, 2 , 2, 4 , * 2, 4 , * 1, 2
1  Department of Agricultural Chemistry and Food Science, Faculty of Science, C/ Francisco Tomás y Valiente, 7. Universidad Autónoma de Madrid, 28049, Madrid, Spain.
2  Department of Production and Characterization of Novel Foods, Institute of Food Science Research, CIAL (UAM-CSIC), 28049 Madrid, Spain
3  Department of Production and Characterization of Novel Foods, Institute of Food Science Research, CIAL (UAM-CSIC), 28049 Madrid, Spain.
4  Department of Agricultural Chemistry and Food Science, Faculty of Science, C/ Francisco Tomás y Valiente, 7. Universidad Autónoma de Madrid, 28049, Madrid, Spain
Academic Editor: Manuel Viuda-Martos

Abstract:

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.

Keywords: Coffee pulp; By-product valorization; Ethanol-modified supercritical carbon dioxide; Flavonoids; Lipids; Food-grade ingredients
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