A sustainable extraction approach for recovery of Rhamnogalacturonan I enriched pectin from Amazonian cocoa pod husk

Approximately 16,000 thousand tonnes of cocoa husk are produced annually worldwide during the chocolate production chain, representing considerable potential for pectin extraction. The aim of this study was to investigate a new extraction technique using a binary system composed of carbon dioxide and water (CO₂ + H₂O) at high pressure and temperature, on cocoa sample from floodplain ecosystem. Temperatures of 393.15 K and 413.15 K and pressures of 20 and 30 MPa were used. Under these combined conditions overall yields ranging from 5.10 % to 10.70 % were obtained. The monosaccharide composition confirmed the extraction of pectic fractions. Uronic acid was identified as the primary monosaccharide (47.2-52.8 %), followed by galactose (19.3-23.6 %) and rhamnose (10.3-13.0 %), which resulted in high percentages of the RG-I region (51.2-44.3 %), which was significantly more prevalent in the extracts obtained with the CO₂ + H₂O binary system compared to traditional methods. The protein and phenolic contents were lower than found for pectins previously extracted with boiling water from the same raw material. The condition of 413.15 K/20 MPa yielded a pectic fraction with the highest degree of purity (91.05 % ± 0.95 %). The extracted pectins had a low degree of methyl esterification (18.8-22.6 %) and a high degree of acetylation (45.7-52.1 %). The molecular weight of the polysaccharides was in the range of 3.0 × 10⁵ to 5.4 × 10⁵ g/mol. The results demonstrated that the CO₂ + H₂O binary system is an efficient approach for the sustainable utilization of cocoa pod husk as a source of rhamnogalacturonan I enriched pectins with features that favour the applications as emulsifier agent in the food and pharmaceutical industries.