Exploring the effect of Curdlan and xanthan on physicochemical properties and multiscale structure of rice starch during extrusion

Hydrocolloids are utilized in starch-based foods for water-holding, thickening, and gelation, yet their molecular interactions with starch in extrusion systems remain underexplored; this study evaluates physicochemical and multiscale structural changes in extruded starch incorporating curdlan (CG) and xanthan (XG). Incorporation of CG and XG significantly counteracted the disruption of the multiscale structure of starch caused by the extrusion treatment, and increased the content of resistant starch. It reduced the content of rapidly digestible starch in extruded starch by 4.99–12.40 %, especially CG (7.99–12.40 %). The retrogradation of ERS was inhibited and the Mw of amylopectin was increased (Mw: 2.39–4.43 × 10⁸ Da), which decreased pasting viscosity. Relative crystallinity (RC) and short-range ordering were reduced by 1.59–3.32 %, and 0.12–0.23, respectively. While XG produced the opposite effects, the enthalpies of retrogradation (14 d) and the RC of ERS-XG increased by 0.22–1.36 J/g and 3.94–4.63 %, respectively. The molecular weight of the complex was increased and the granule structure was denser, especially for CG. This study may provide theoretical basis for complying with the development trend of extruded starch for great health.