Pressurized liquid extraction for the recovery of alkaloids from cocoa pod husk

Abstract

Cocoa pod husk (CPH), which makes up to 76 % of the cocoa fruit mass, is the main waste product of the cocoa chain and holds untapped potential due to its alkaloid content and antioxidant activity. Therefore, this work aimed to explore the sustainable use of CPH by recovering alkaloids by pressurized liquid extraction (PLE), evaluating the effects of temperature, solvent composition, solvent/feed ratio, and their interactions. PLE was performed following an experimental face-centered design that evaluated temperature (80, 100, and 120 °C), solvent mixtures of ethanol in water (50, 75, 100 % ethanol (w:w)) and solvent/feed ratio (3, 6, 9 kg solvent/kg CPH) at a pressure of 10.0 ± 0.5 MPa. Maceration and ultrasound-assisted extraction were performed with the same solvent mixture and solvent/feed ratio of the best PLE condition (120 °C, 50 % EtOH, and 9 kg solvent/kg CPH). The extracts were compared in terms of global yield (X₀) (3.36–18.00 %, w/w), total reducing capacity (TRC) (0.99–11.62 mg gallic acid equivalent (GAE)/g CPH), alkaloids content (theobromine: 1.1–6.7 mg/g CPH; caffeine: 0.50–1.57 mg/g CPH), ferric reducing antioxidant power (FRAP) (0.01–24.04 mg trolox equivalent (TE)/g CPH), and oxygen radical absorbance capacity (ORAC) (2.68–37.09 mg TE/g CPH), in which PLE stood out compared to conventional extractions. The results demonstrated that temperature, solvent composition and solvent/feed ratio significantly influenced PLE of CPH, highlighting the effectiveness of hydroalcoholic mixtures and high temperatures. To sum up, PLE is a promising strategy for the sustainable valorization and functional food applications of CPH.