Valorisation of coffee husk for functional arabinogalactans: A sustainable value-added ingredient

Coffee husks, an underutilized byproduct (∼18 % of the dry weight of coffee cherry) contain ∼58 % polysaccharides. Despite their abundance, the physico-chemical composition, structure, and their bioactivities remain largely unexplored. This study investigates the valorisation of coffee husks to extract polysaccharides using an alkali extraction (0.4 M NaOH, 1:10 substrate-to-solvent ratio, 55 °C, 6 h) yielding an arabinogalactan-rich polysaccharide (12.83 ± 2.44 %) with 84.49 % total carbohydrates. It is predominantly composed of galactose (44.77 %) and arabinose (33.57 %) and had a molecular weight of 121 kDa. Characterization via FTIR, XRD, ¹H NMR, and DSC revealed a semi-crystalline structure, thermal stability, and typical carbohydrate patterns. Physicochemical analysis showed water holding (23.8 g/g), oil holding (13.2 g/g), and swelling capacities (2.25 mL/g). Strong antioxidant activity further, emphasizes their potential as functional food ingredients. This study presents an efficient extraction method for utilizing coffee husks as a sustainable resource.