Partially gelatinized extruded yam starch improves wheat dough rheology and microstructure through enhanced...

Although previous studies have demonstrated the effectiveness of extrusion in starch modification, the mechanism by which changes in the degree of gelatinization (DG) influence the physicochemical properties of starch and its subsequent functionality in the dough system remains poorly understood. This study produced yam starches with different DGs (10.47 %, 35.79 %, 69.58 %, 96.58 %) using a twin-screw extruder under different temperatures (80, 90, and 100 °C), and water contents (30 %, 45 %, and 60 %), and systematically investigated the effect of DG on the microstructure and rheological properties of wheat dough. Results showed that increasing DG improved the hydration properties of yam starch, as evidenced by a higher water absorption index, water solubility index, and swelling power. These improvements were attributed to the disruption of the long- and short-range ordered structures of starch, leading to reduced relative crystallinity. Concurrently, structural modifications led to an increase in the mean particle size (D_4,3) and accelerated thermal decomposition. When incorporated into wheat dough, the functional effect of yam starch depended on its DG. Partially gelatinized starch (DG = 69.58 %) significantly increased the storage and loss modulus, indicating improved dough viscoelasticity. SEM and CLSM observations revealed that partially gelatinized starch granules integrated tightly within the gluten matrix, forming a continuous composite network that enhanced the dough's resistance to deformation. However, fully gelatinized starch (DG = 96.58 %) disrupted gluten network continuity through intense water competition, resulting in a significant decrease in dough stability time. Overall, this study elucidates the mechanism by which extrusion-induced changes in the DG of yam starch affect its physicochemical characteristics and functional performance in wheat dough, providing theoretical guidance for developing yam starch as a functional ingredient for improving dough quality through extrusion technology.