Power-dependent structural transformation in highland barley starch via ultrasonication: From disruption to reassembly for enhanced resistance to digestion

The purpose of this study is to examine the mechanisms by which ultrasonication regulates the multiscale structure and physicochemical properties of highland barley starch (HBS) and to systematically explain the relationships between the four structural levels (particles, layers, crystals and molecular chains) and in vitro digestibility. The results revealed that ultrasonic treatment induced a tri-fold effect on the structure of HBS: disruption-reorganization-disintegration. At appropriate ultrasonic power levels (400–500 W, particularly 500 W), the multiscale structure of HBS transitions from a disruption-dominated state to a reorganization-dominated state. This process drove molecular chain rearrangement, leading to the recovery of double-helix and crystalline order, and was accompanied by partial reorganization of the branching-point network. This restructured architecture improved the swelling power, solubility and rheological properties of HBS, enhanced the thermal stability of the system. This robust physical barrier inhibited digestive enzyme activity, increasing the resistant starch (RS) from 9.12% to 18.35%. This study expands the potential applications of ultrasonic modification in the food industry. The ultrasonically modified HBS may have potential as a food ingredient for developing low-glycemic-index products.