Multi-scale hierarchical regulation of starch chain length distribution and its consequential impact on starch digestibility: From molecular structure to granular degradation.

Starch chain length distribution (CLD) hierarchically modulates starch digestibility from enzyme recognition to granular degradation. This review summarizes CLD characteristics of amylose (short, medium, long chains) and amylopectin (A, B1, B2, B3 chains). The hierarchical regulatory rules are elucidated at molecular (chain flexibility, hydrogen bonding), aggregated (double helix, crystalline-amorphous regions), and granular (morphology, pores) scales. It further clarifies how distinct CLD profiles dynamically modulate the proportions of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) by modulating enzyme accessibility and hydrolysis kinetics through hierarchical structures. Precise CLD regulation technologies (molecular modification, physical processing, biological regulation) and their digestibility modulation effects are summarized. Finally, key controversies (cross-scale transfer mechanisms of CLD regulation from molecular conformation to granular degradation, in vitro-in vivo discrepancy) and future directions (multi-scale characterization, precision low-glycemic index(low-GI) design) are outlined, providing a theoretical basis for functional starch foods.