Effects of Different Degrees of Gelatinization on Structural, Physicochemical and Digestive Properties of Kudzu Starch

Kudzu (<i>Pueraria</i> spp.) starch, valued for its transparency, viscosity, and stability, has broad potential in functional and instant food applications. However, its limited cold-water solubility and inconsistent functional performance across cultivars hinder wider utilization. To improve its processability and nutritional functionality, this study aimed to elucidate how the degree of gelatinization (DG)-a structural indicator of starch transformation-can be precisely controlled and used to modulate starch properties. Starches from two typical kudzu cultivars, K10 (<i>Pueraria thomsonii</i>) and K27 (<i>Pueraria lobata</i>), were subjected to hydrothermal treatment (45-95 °C) to obtain samples with defined DG levels. DG was quantitatively determined by enzymatic assay, differential scanning calorimetry (DSC), and iodine-binding analysis, enabling method cross-validation. Increasing DG enhanced iodine complexation capacity, elevated gelatinization temperatures, and reduced enthalpy change and crystallinity. K27 exhibited more pronounced physicochemical transitions at lower DG than K10, indicating cultivar-specific sensitivity. In vitro digestion revealed that hydrolysis kinetics gradually approached and eventually conformed to a first-order model as DG increased, confirming a DG-dependent shift in digestibility. These results establish DG-rather than processing temperature-as the primary factor governing kudzu starch functionality and provide a methodological basis for designing starch-based foods with tailored glycemic and textural properties.