Unlocking value from cocoa bean shell: Dimethyl ether extraction of lipids and bioactive compounds

Cocoa bean shell (CBS), a byproduct of cocoa processing, contains considerable amounts of lipids and bioactive compounds and is therefore a promising feedstock for valorization. In this study, dimethyl ether (DME), a green solvent with medium polarity and low boiling point, was employed for CBS extraction and compared with conventional Soxhlet extraction using n-hexane and 80% ethanol. DME extraction was conducted at 303–333 K, 2–8 MPa, and 30–110 min, and the effects of process conditions were evaluated using response surface methodology. The extraction yield of DME ranged from 28.63% to 34.33%, and the highest yield and fatty acid content were obtained at 333 K, 8 MPa, and 110 min, reaching 34.33% and 383.37 mg g −1 CBS, respectively. The extracts were mainly composed of lipid-derived compounds, particularly palmitic, stearic, and oleic acids, while methylxanthines such as theobromine and caffeine were detected in DME and ethanol-water extracts. Theobromine was the most abundant identified bioactive compound. These results demonstrate that DME is a promising alternative solvent for CBS valorization, combining high lipid recovery, mild operating conditions, and facile solvent separation.