Integrated Green Valorization of Coffee Cherry Pulp Through Bioactive Compound and Pectin-Rich Fraction Recovery for Pectic Oligosaccharide Production

Coffee cherry pulp (CCP), a major by-product and solid waste of coffee processing, is rich in phenolic compounds and pectin but remains underutilized. This study evaluated supercritical CO2 extraction with ethanol co-solvent (SFE-CO2) as a green alternative for recovering bioactive compounds from CCP and investigated the subsequent recovery of pectin-rich fractions and pectic oligosaccharides (POS). Using a one-factor-at-a-time (OFAT) approach, the selected SFE-CO2 conditions were 50% (w/w) ethanol, 55 °C, and 300 bar. Under these conditions, the SFE-CO2 extract exhibited total phenolic (4.26 ± 0.31 mg GAE/g extract) and total flavonoid contents (394.9 ± 10.5 μg QE/g extract) that were 1.6–5.4-fold higher than those of the hot-water and ethanol extracts. Antioxidant activities differed among extraction methods, with the SFE-CO2 extract showing higher activities in the DPPH and FRAP assays but lower ABTS radical-scavenging activity than the conventional extracts. In vitro DPP-IV inhibition (58.6–69.8% at 1.5 mg GAE/mL) did not differ significantly among the extracts. Untargeted UHPLC-MS/MS-based metabolomics (262 features) revealed distinct metabolite profiles among the extraction methods, with SFE-CO2 extracts enriched in chlorogenic acid, caffeoylquinic acid, and coumaroylquinic acid, indicating extraction-dependent selectivity. Hot-water pretreatment reduced the yield of the pectin-rich fraction obtained by microwave-assisted extraction to ≤8%, whereas ethanol- and SFE-CO2-treated residues yielded approximately 18–20%, comparable to untreated CCP. The SFE-CO2-treated residue yielded 10.88 ± 0.70% at 0.002% citric acid, comparable to the highest yield of untreated CCP at 0.2% citric acid (10.77 ± 0.34%). Enzymatic hydrolysis of the CCP-derived pectin-rich fractions released POSs with DP 1–4. Overall, the findings demonstrate the potential of an integrated green extraction strategy to enhance the utilization of CCP by combining selective bioactive compound recovery with downstream valorization of the residual biomass for the production of a pectin-rich fraction and pectic oligosaccharides, thereby contributing to the circular bioeconomy and sustainable utilization of coffee-processing by-products.