Structural transformation of brewer's spent grain hemicellulose under oxidative delignification characterized by...

Detailed structural analysis of dietary fibers, particularly glycosidic linkages and monosaccharide composition, is essential for understanding how processing methods influence nutritional function and commercial viability. This study investigates how mild oxidative delignification using an optimized ultrasound-microwave assisted peracetic acid (UMAP) bleaching process remodels hemicellulose architecture in brewer's spent grain (BSG) fiber. The aim is to enhance fiber whiteness while preserving key polysaccharide structures, particularly soluble hemicelluloses like arabinoxylans and β-glucans. Structural characterization was performed using scanning electron microscopy (SEM), Congo Red assays, and ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-QqQ-MS/MS). In RawBSG fiber, 57 glycosidic linkages and 13 monosaccharides were identified, whereas UMAP-treated fiber retained 44 linkages- substantially more than the 25 observed in chlorine-enzymatic hybrid bleaching. UMAP selectively removed complex side-chain residues (e.g., 2,3-f-Ara, 2,5-f-Ara) while preserving terminal arabinose residues and critical xylan backbones (4-Xylp, T-Xylp). It also enhanced specific glucose and mannose linkages (e.g., 2,3,6-Glc, T-Man), indicating structural remodeling without extensive degradation. These findings demonstrate that UMAP bleaching is an effective, scalable method for producing visually appealing, nutritional dietary fiber from BSG, with superior structural preservation compared to conventional bleaching. These findings demonstrate that UMAP bleaching is not only effective and scalable but also preserves nutritional fiber structures, offering a promising route for upcycling BSG into high-value, clean-label ingredients for functional foods.