Decreasing the digestibility of debranched corn starch by encapsulation with konjac glucomannan

The aim of this study was to develop low-digestibility debranched corn starch/konjac glucomannan composites (DCSK) and investigate their physicochemical properties, including the crystallographic, rheological, and morphological characteristics, solubility and swelling power. The relative crystallinity of the DCSK samples was remarkably higher than that of debranched corn starch (DCS), although it slightly decreased with increasing konjac glucomannan (KGM) content. The addition of a large amount of KGM inhibited the long-term retrogradation of DCS. The apparent viscosity of the system was enhanced after KGM incorporation. Owing to the encapsulation of DCS by KGM, the solubility of the system decreased while the swelling power increased. In vitro digestion results indicated the digestibility of the DCSK samples was significantly lower than that of the DCS sample. A first-order hydrolysis kinetic model revealed the digestion rate of the DCSK samples was lower than that of the DCS sample, suggesting that KGM hindered the attack of the starch by digestive enzymes. Scanning electron microscopy (SEM) images demonstrated the surfaces of DCSK became smoother and more compact upon coating with KGM. Furthermore, confocal laser scanning microscopy images (CLSM) provided direct evidence for the encapsulation of DCS by KGM in the DCSK composites. The described method may represent a promising strategy for decreasing the digestibility of starch.