Distinct mechanisms of dry and wet ball milling on foxtail millet starch: From physical agglomeration to molecular...

Although effective for modifying starch properties, the comparative mechanisms of dry and wet ball-milling on multi-scale structure of foxtail millet starch remain unclear. This study aimed to elucidate their distinct structural and physicochemical alterations. Dry ball-milling primarily caused physical agglomeration, with only limited and non-monotonic damage of the starch's internal structure. In contrast, wet ball-milling facilitated the systematic deconstruction of the starch architecture, characterized by granule fragmentation, substantial reduction of both long- and short-range order, and significant molecular depolymerisation. This depolymerisation was found to occur via a 'mechano-debranching' mechanism. Consequently, wet ball-milling treatment significantly increased water solubility and swelling power, but compromised pasting viscosity, gel strength (G'), hardness and setback. The effects of dry ball-milling were moderate by comparison. The established structure-function relationships provide a robust theoretical basis for precisely tailoring foxtail millet starch functionalities for specific food applications, such as developing highly soluble, anti-retrogradation ingredients.