Structural, physicochemical, and digestive properties of enzymatic debranched rice starch modified by phenolic compounds with varying structures

Abstract

The physicochemical properties of starch and phenolic acid (PA) complexes largely depend on the effect of non-covalent interactions on the microstructure of starch. However, whether there are differences and commonalities in the interactions between various types of PAs and starch remains unclear. The physicochemical properties and digestive characteristics of the complexes were investigated by pre-gelatinization of 16 structurally different PAs and pullulanase-modified rice starches screened. FT-IR and XRD results revealed that PA complexed with debranched rice starch (DRS) through hydrogen bonding and hydrophobic interaction. Benzoic/phenylacetic acid with polyhydroxy groups could enter the helical cavities of the starch chains to promote the formation of V-shaped crystals, and cinnamic acid with p-hydroxyl structure acted between starch chains in a bridging manner, both of which increased the relative crystallinity of DRS, with DRS-ellagic acid increasing to 20.03 %. The digestion and hydrolysis results indicated that the acidification and methoxylation of PA synergistically decreased the enzyme activity leading to a decrease in the digestibility of the complexes, and the resistant starch content of the DRS-vanillic acid complexes increased from 28.27 % to 71.67 %. Therefore, the selection of structurally appropriate PAs can be used for the targeted preparation of starch-based foods and materials.