Multi-scale structural evolution of colored whole-wheat doughs and breads: protein secondary structure, starch crystallinity, and 3D crumb architecture

Colored wheat is rich in natural pigments and bioactive compounds, but its processing adaptability in whole-wheat fermented products remains unclear. This study compared the multi-scale dough structure and bread crumb architecture of common wheat dough (NCG), green wheat dough (GWD), blue wheat dough (BWD), purple wheat dough (PWD), and red wheat dough (RWD). Dynamic rheology, fermentation rheology, low-field nuclear magnetic resonance (LF-NMR), texture profile analysis (TPA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), sulfhydryl/disulfide bond (SH/S–S) analysis, confocal laser scanning microscopy (CLSM), and X-ray computed tomography (CT) were used to characterize dough network formation, water mobility, molecular structure, microstructure, and crumb pore characteristics. Wheat variety influenced dough viscoelasticity, fermentation behavior, water distribution, protein secondary structure, starch crystalline structure, and final bread pore structure to different extents. GWD showed relatively high viscoelastic moduli, the highest strongly bound water proportion, favorable textural properties, and relatively high volumetric porosity, indicating a favorable balance between network strength, water binding, and pore formation. BWD exhibited the highest total gas production and volumetric porosity, but its lower gas retention efficiency and pore density suggested that gas production was not fully converted into numerous small pores. PWD had the highest protein, total phenolic, and anthocyanin contents, together with relatively high β -sheet content, S S content, and relative crystallinity, but showed poor gas retention and the lowest volumetric porosity. RWD produced a small-pore-dominated crumb structure with the highest pore density. Overall, colored whole-wheat doughs exhibited variety-dependent multi-scale structural differences, which were reflected in fermentation performance and final crumb architecture.