Curdlan enhances the structural stability and functional properties of sweet potato starch gels: Mechanistic insights from gelatinization, retrogradation, and multiscale characterization

Sweet potato starch (SPS) gels often exhibit poor thermal stability and textural quality at low solid concentrations. This study investigated the mechanism by which curdlan (CD), a microbial β-(1,3)-glucan with unique thermoirreversible gelling properties, modulates the gelatinization, retrogradation, rheology, structure, and gel properties of SPS. Incorporating CD delayed SPS gelatinization, reduced gelatinization enthalpy (ΔH), and enhanced the thermal and shear stability of the paste, attributed to competitive hydration and robust SPS-CD interactions. Crucially, CD accelerated gel network formation during cooling, fostering stronger intermolecular hydrogen bonding (confirmed by FTIR redshift) and hydrophobic associations. Multi-scale structural analysis (SEM, SAXS) revealed that 5 % CD produced a composite gel with a significantly denser microstructure, smaller pore size, and higher fractal dimension. Consequently, this optimized structure yielded superior mechanical properties (increased storage modulus G′, hardness, chewiness), enhanced water retention (LF-NMR), and improved gel stability. Composite gels with 5 % CD exhibited optimal overall properties (hardness ↑ 56.43 %, chewiness ↑ 55.62 %, water retention ↑ 15.09 %, gel thermal stability ↑ 18.31 %). These findings demonstrate that CD effectively modifies the structural assembly dynamics and intermolecular interactions within SPS gels, providing a fundamental basis for developing high-quality, stable SPS-based gel products with enhanced functional attributes.