The starch-polyphenol inclusion complex: Preparation, characterization and digestion

Debranched rice starch and different polyphenols, including genistein, quercetin, naringin, gallic acid, ferulic acid and caffeic acid, formed the V-type inclusion complex, which was confirmed by diffraction peaks at 7.5°, 13.0° and 20.0° and the presence of the endothermic peak during DSC analysis. Moreover, the inhibitory effect of polyphenols on α-amylase was in the order of quercetin > genistein > gallic acid = ferulic acid > naringin = caffeic acid, and their inhibitory effect on amyloglucosidase was in the order of quercetin = naringin > gallic acid > caffeic acid = genistein > ferulic acid. The starch-genistein and starch-naringin complexes had the highest polyphenol content, followed by the starch-ferulic acid complex, the starch-caffeic acid complex, the starch-quercetin complex and the starch-gallic acid complex. The resistant starch content of starch-genistein, starch-quercetin, starch-naringin, starch-gallic acid, starch-ferulic acid and starch-caffeic acid complexes was 72.49%, 79.86%, 68.82%, 60.96%, 71.06% and 71.24%, respectively. These results suggested that these starch-polyphenol inclusion complexes were highly resistant to digestion. Particularly, the starch-quercetin complex was the most resistant, which might be due to that its highest crystallinity and the strongest inhibitory effect of quercetin on amylases.