Multi-scale structure and digestible process of wheat starch as affected by distribution behavior of rice glutelin amyloid fibril aggregates during gelatinization and digestion

Abstract

The effect of distribution behaviors of rice glutelin amyloid fibril aggregates (RAFA) on the structures and digestible process of wheat starch was investigated, and the interaction was revealed by molecular dynamics simulations. Rice glutelin (RG)/RAFA enhanced the long-range ordered structure of starch, and the relative crystallinity of gelatinized RAFA-wheat starch reached 14.35 %. Moreover, the RAFA was more effective than RG in improving the short-range ordered structure of starch. Simultaneously, the RAFA exhibited higher cross-linking with starch than the RG, forming continuous and compact network structures that encapsulated the starch. After 180 min of in vitro pancreatic digestion, the residual RAFA encapsulating the starch was still observed in the chyme, hindering amylolytic enzyme action and alleviating the starch digestibility. Molecular dynamics simulations further confirmed that the RAFA, compared to the RG, bound more readily to the starch molecule and formed more stable complexing structure. And the RAFA formed hydrogen bonds with the hydroxyl groups of starch through polar amino acid residues (Gln and Asn) and nonpolar residues (Ala, Gly, and Ile) with binding free energy of -263.868 kJ/mol, while that of the RG-starch was -28.798 kJ/mol. The study enriches the theory of regulating starch digestion using food-derived protein amyloid fibril aggregates.

Keywords: Inhibition mechanism; Protein amyloid fibrils; Protein-starch interaction.