Short-chain amylopectin and long-chain amylose drive distinct wheat starch gel networks with similar low digestibility.

Reducing staple-food digestibility is an important nutritional target for wheat starch-based products, yet how starch chain architecture regulates gel digestibility remains unclear. In this study, starches from 14 wheat varieties were used to prepare 40% (w/w) gels, and their gel structure, in vitro digestibility, and chain-length evolution during digestion were investigated. The results showed that elevated short-chain amylopectin or long-chain amylose produced gel networks with different macroscopic mechanics but similar local barrier function, yielding comparable digestion rates and lower final digestibility (77.71% and 79.72%, respectively). A high proportion of short-chain amylopectin promoted densely packed A-type double helices through high viscosity and a uniform hydrogen-bonding environment, forming a homogeneous barrier against enzyme diffusion and hydrolysis. In contrast, long-chain amylose more readily reorganized with amylopectin into a stable semicrystalline continuous network, whose resistance also arose from dense internal order. The enrichment of DP 24-34 and DP 44-58 chains in digestion residues further indicates that these fractions were major contributors to enzyme resistant structures. DP 24-34 chains favored local ordered lamellae, whereas DP 44-58 chains acted as internal supporting scaffolds. This study provides key approaches for tailoring starch digestibility through molecular design.