Valorization of metabolite-enriched carbohydrates from Theobroma biomass via ultrasound-assisted alkaline extraction

Polysaccharides, widely used in food, pharmaceutical and industrial sectors, are abundant in Theobroma species pod husk waste (T. cacao, T. grandiflorum and T. bicolor). This study examined alkaline extraction using NaOH and KOH with ultrasound assistance to assess the physicochemical and functional properties of the resulting polysaccharides and non-polysaccharides components. The extraction yields of these components varied, with T. cacao-NaOH yielding the highest recovery (38.0 %), followed by T. bicolor-NaOH (14.7 %) and T. grandiflorum-NaOH (8.0 %). NaOH-extracted materials exhibited galacturonic acid content up to 40 %, molecular weight of ∼783 kDa and esterification degree of 38.1 %, while KOH-based extraction retained higher levels of rhamnose (18.0 %) and xylose (28.3 %). Materials extracted via KOH preserved metabolites like proanthocyanidins (1.58 mg catechin equivalent/g in T. grandiflorum), whereas NaOH extraction resulted in greater antioxidant activity, particularly in T. cacao with 127.8 mmol Fe2+/g and 3.26 M Trolox equivalent/g in FRAP and ORAC assays. Rheology showed that polysaccharides extracted from T. cacao and T. bicolor exhibited highest viscosity and gel strength (G′ > G″), while those from T. grandiflorum had lower viscosity. Thermal analyses confirmed that NaOH extractions produced stable, gel-forming polysaccharides associated with pectic components. These findings highlight Theobroma pod husks as a valuable waste source for revalorization.