Β-Glucanase-driven changes in β-glucan structure and metabolism throughout Hull-less barley dough fermentation

Hull-less barley is an important staple crop in plateau regions; however, its elevated β-glucan (BG) content often compromises dough quality. In this study, we investigated the mechanisms underlying β-glucanase (BGS)-mediated enhancement of hull-less barley dough quality by integrating structural characterization and untargeted metabolomics. BGS hydrolyzed BG glycosidic bonds, reducing its molecular weight from 6.577 × 10⁵ to 7.247 × 10⁴ Da and median psize (D₅₀) from 895.67 to 321.67 nm, thereby disrupting hydrogen bonding and lowering viscosity. Untargeted metabolomic analysis identified 768 metabolites, with BGS treatment significantly upregulating the levels of organic acids, lipid-like molecules, and organic oxygen compounds. D₅₀ exhibited significant negative correlations with amino acids associated with the umami taste, including glutamate and aspartate. These findings suggest that BGS-mediated BG depolymerization enhances substrate accessibility for enzymes and yeast; provides oligosaccharides as carbon sources; and promotes protein hydrolysis, lipid oxidation, flavor formation, and yeast fermentation.