How hydrocolloid molecular features modulate lotus rhizome starch digestibility and retrogradation: A structure-function study.

Abstract

Lotus rhizome starch (LS) has limited application owing to its high digestibility and pronounced retrogradation tendency. To elucidate how hydrocolloid molecular architecture regulates LS functionality after gelatinization, fully gelatinized LS was blended with pre-hydrated xanthan gum (XG), flaxseed gum (FG), guar gum (GG), or carrageenan (CA). Multiscale structural and functional analyses, including microstructure, nanoscale morphology, rheology, and water distribution, were performed to evaluate the ability of hydrocolloids to spatially integrate with the gelatinized LS matrix and organize coherent networks. XG formed a highly integrated interpenetrating network that effectively restricted molecular mobility and enzyme accessibility, resulting in improved control of starch digestion. FG generated a heterogeneous yet stable network that enhanced structural confinement and water regulation, leading to the strongest inhibition of retrogradation and increased resistant starch formation. In contrast, GG formed a weaker network with limited effects on digestion regulation, whereas CA exhibited poor integration with the LS matrix because of phase separation. These findings demonstrate that the functional performance of hydrocolloids is determined by the combined effects of molecular architecture and their ability to integrate with the gelatinized starch matrix, providing a structural basis for designing starch-based foods with improved storage stability and tailored digestibility.