A-type and B-type starch separated from waxy wheat starch were separately mixed with high-amylose corn starch and treated with pullulanase and/or branching enzymes. The granular morphology, crystalline structure, apparent amylose content, solubility, swelling power and other physicochemical properties of the modified starch were determined, and their digestion characteristics were also investigated. The results showed that the predicted glycemic index (pGI) of waxy wheat A- and B-type starch were significantly reduced by the dual-enzymatic modification, and the content of apparent amylose was increased significantly. The solubility increased with temperature, while the swelling power remained basically unchanged. Under a scanning electron microscope (SEM), the microstructure of the enzymatically modified starch granules exhibited holes. The relative crystallinity (RC) and the ratio between the intensities of the peaks at 1047 and 1022 cm^-1 were obtained by X-ray diffraction and Fourier infrared spectroscopy, respectively, revealing that the long-range and the short-range ordered structures of starch were significantly improved by the dual-enzymatic modification. Furthermore, sequential treatment with pullulanase and branching enzymes could significantly improve the digestion characteristics of waxy wheat A-type and B-type starch.

In this study, free radical oxidation was chosen to induce covalent reaction of gliadin (GL) with epigallocatechin gallate. The effects of different ultrasound (US) powers on the enhancement of the covalent reaction were compared with the aim of improving the bioavailability of polyphenols in protein modification. Covalent modification of polyphenols was verified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), high-performance liquid chromatography (HPLC) and the Folin-Ciocalteu assay. The structural changes of the covalent complexes were analyzed by ultraviolet (UV) spectroscopy and circular dichroism (CD) spectroscopy. The results showed that US disrupted weak intra-protein forces, which caused molecular depolymerization. The hydrophilic/hydrophobic amino acid residues of the protein were shifted and the tertiary structure tended to be looser, and this process altered the distribution of groups on the molecule surface and increased the water solubility of the protein. Furthermore, the shift in the spatial structure of GL resulted in the exposure of more enzyme cleavage sites, making its digestion easier. The synergistic effect of US and free radical oxidation increased the loading of antioxidant molecules onto the covalent complexes, resulting in stronger free radical scavenging activity.