Microstructure-informed stage characterization of wheat endosperm refinement during shear comminution

Structural evolution of wheat endosperm particles during comminution can markedly influence flour processing and digestibility. While previous studies have mainly focused on differences among grinding endpoints, stage-dependent refinement under shear-dominant conditions remains unclear. This study characterized the structural and functional evolution of wheat endosperm particles during shear-dominant comminution. Coarse wheat endosperm particles were collected after predefined shear durations during shear-dominant comminution and examined using scanning electron microscopy and confocal laser scanning microscopy (CLSM), as well as based on particle-related physicochemical indices, protein structural parameters, rapid visco analyzer properties, and in vitro starch digestibility. CLSM image-based deep-learning analysis was performed to characterize microstructural features at different comminution stages. The refinement process could be operationally divided into a volume grind stage (RM-S40) and a surface grinding stage (S50-S70). Comminution increased the proportion of damaged starch (from 0.22% to 7.97%), decreased the particle size, and progressively enhanced the specific surface area. Additionally, comminution increased the peak viscosity (from 1517 cP to > 2300 cP) and rapidly digestible starch proportion (from 11.29% to 32.83%) and decreased the resistant starch proportion (from 74.32% to 50.99%). Analysis of protein-related indices further indicated the disruption and partial reorganization of gluten aggregation during shear comminution. The ResNet18 model achieved a test accuracy of 0.952. The resulting image-derived descriptor exhibited good consistency with key physicochemical and functional indicators. Thus, the refinement of wheat endosperm during shear-dominant comminution was not uniform and was accompanied by stage-dependent microstructural evolution and corresponding functional changes.