Insights into the effects of microscopic fractal features, supramolecular structures on digestibility of retrograded...

The digestibility of starch gels is closely associated with their microstructure, yet quantitative understanding remains limited. Starch gels prepared from wheat, high-amylose wheat, corn, high-amylose corn, potato, pea, and sweet potato starches were investigated using fractal analysis, DSC, ATR-FTIR, XRD, and digestion kinetic. Six starches were evaluated at 10%, 20%, and 30%, whereas high-amylose corn starch was tested at 15%, 25%, and 35% because it did not form a stable, testable gel at 10%. Increasing starch concentration was generally associated with greater microstructural complexity and structural order. Pore fractal dimension (D_f) was strongly positively correlated with the rapid-phase digestion rate (k₁) and negatively correlated with the slow-phase rate (k₂) and fitted asymptotic hydrolysis extent (C_∞). Thus, pore D_f represents a structural indicator strongly associated with starch digestibility. These findings clarify relationships between gel structural characteristics and starch digestion, providing a basis for designing starch-based foods with tailored digestibility.