Insights into the effects of caffeic acid and amylose on in vitro digestibility of maize starch-caffeic acid complex.

ABSTRACT

Starch digestibility can be decreased by phenolic acids. The physicochemical and digestive properties of high-amylose maize starch, normal maize starch (NMS) and waxy maize starch (WMS) complexed with caffeic acid (CA) were investigated to determine the effects of CA and amylose on starch digestibility. CA inhibited the activity of α-glucosidase and α-amylase in a dose-dependent manner. The inhibitory effect of CA on α-glucosidase was reversible and anti-competitive, while that on α-amylase was irreversible. With the increase of the amylose content in starches, the complexing index of starch-CA decreased, while the relative crystallinity increased. The crystallinity of all three starches decreased after incorporating CA, and the hydroxyl peak in the 1H-NMR spectrum of the WMS-CA complex increased significantly. The resistant starch content of the WMS-CA and NMS-CA complexes increased significantly compared with the control. The inhibitory effect of CA on amylolytic enzymes played a major role and the change of starch structure exhibited a minor role in the digestibility of the maize starch-CA complexes.