Bacillus subtilis fermentation improves the structural, textural and volatile properties of whole-wheat dough and steamed buns

Whole-wheat products often suffer from poor texture and off-flavors due to bran-mediated gluten disruption. This study examined the physicochemical changes associated with Bacillus subtilis fermentation of whole-wheat dough. Four B. subtilis strains were applied, and rheology, intermolecular forces, microstructure, pasting behavior, physical and textural properties and volatile metabolites were evaluated. Fermentation reduced apparent viscosity and increased creep recovery, which is consistent with a more deformable dough. The protein fractions attributed to hydrogen and disulfide bonding increased, whereas those attributed to ionic and hydrophobic interactions decreased. Fourier-transform infrared and microscopic analyses indicated changes consistent with re-established hydrogen bonding, higher short-range starch order, and a more continuous protein phase. Fermented steamed buns exhibited higher specific volume and porosity, reduced hardness, and a softer crumb structure. Volatile metabolomics showed lower relative odor activity values of lipid-oxidation- and lignin-derived off-odorants and higher levels of aromatic alcohols. Multivariate analysis identified strain SH as the most effective. Overall, B. subtilis fermentation may offer a practical route to improve the structural and instrumentally measured flavor-related properties of whole-wheat systems.