Ultrasound-assisted processing of low-molecular-weight soybean okara fraction: Metabolomic profiles, antioxidant activities and trans-epithelial transport in a Caco-2 intestinal model

This study investigated the effects of ultrasound-assisted processing on the metabolomic profile, antioxidant properties, and trans-epithelial transport of low-molecular-weight fraction (<3 kDa) derived from ultrasound-treated soybean okara using an in vitro Caco-2 cell model. Untreated (OKARA-C) and ultrasound-treated (OKARA-US) samples were analyzed by untargeted high-resolution metabolomics to assess changes in metabolite composition, apical availability, and trans-epithelial transport. Ultrasound processing significantly increased the abundance of low-molecular-weight metabolites, including organic acids, amino acids, nucleotides, and redox-related cofactors such as riboflavin and flavin mononucleotide. At the apical level, secondary metabolites were preserved without undergoing metabolic transformation, thereby maintaining their intestinal cell bioavailability. Antioxidant assays demonstrated an enhanced antioxidant capacity of OKARA-US. Overall, this study provides the first comprehensive metabolomic evidence that ultrasound-assisted processing enhances both the bioactive composition and the trans-epithelial transport of selected metabolites, supporting its valorization as a sustainable and functional food ingredient derived from agro-industrial by-products.