Physical field excitation to modify Cyperus esculentus starch and its complex with EGCG: Multiscale structural changes and digestive behavior

Abstract

Starch-polyphenol modify starch structural and functional properties while enhancing polyphenol stability and bioavailability. Therefore, this study examined the complexation of epigallocatechin gallate (EGCG) with Cyperus esculentus starch (CES) modified with dielectric barrier discharge plasma (DBDP) and microwave (MW). The results revealed that EGCG formed non-inclusion complexes with CES through hydrogen bonding, occupying hydroxyl sites between starch chains and disrupting intra- and intermolecular interactions. Additionally, DBDP and MW treatments altered CES morphology, facilitating complexation and causing particle enlargement and structural disruption. Consequently, multiscale structural analyses revealed reduced molecular order and helix integrity, supporting hierarchical rearrangement within CES-EGCG. These changes led to reduced crystallinity and thermal stability, particularly in MW-treated samples, where conformational loosening increased swelling power and lowered pasting viscosity. Consistently, CES-EGCG exhibited reduced gel elasticity and viscosity in these samples, as the relaxed network facilitated water penetration and thermal diffusion, enhancing solubility and thermal responsiveness. EGCG also improved freeze-thaw stability by limiting syneresis and reinforcing gel structure. Importantly, multiscale rearrangements limited enzyme accessibility and inhibited its activity, thereby suppressing starch hydrolysis and resulting in a 6–9 % increase in resistant starch. Conclusively, this study elucidated CES-EGCG interactions driven by physical field excitation and highlighted implications for developing functional starch systems.