Insight into the binding mode of different lotus seed natural starch-phenolic acids complexes

This study investigated the influence of natural lotus seed starch on the adsorption of seven endogenous phenolic acids present in lotus seeds. The research delineated the interaction mechanisms and subsequently analyzed the alterations in starch characteristics following adsorption. A comprehensive suite of analytical techniques, including adsorption isotherms, ¹³C NMR, DSC, LF-NMR, rheology, particle size, and potential analyses was employed. All seven phenolic acids were found to spontaneously and physically bind to natural lotus seed starch, primarily through hydrogen bonding, van der Waals interactions, and hydrophobic forces. Post adsorption, the starch granules exhibited diminished crystallinity and reduced bound-water content. Notably, p-coumaic acid, chlorogenic acid, and p-hydroxybenzoic acid formed single helical complexes with the starch, whereas coumalic acid formed non-encapsulated compounds. The adsorption process resulted in increased total color difference (ΔE), particle size, zeta potential, and gelatinization enthalpy of the starch granules, while concurrently decreasing granule-bound water content, glass transition temperature (T_g), and the loss modulus (G″) of the starch pastes. Consequently, the formation of starch-phenolic acid complexes reduces the bound water content, which in turn diminishes the storage modulus and regeneration capability of the starch paste. These findings provide a novel basis for understanding the mechanisms governing the interactions between starch and phenolic acids, thereby elucidating the alterations in the properties of phenolic acid- and starch-rich foods during processing.