Effects of soluble dietary fiber on the crystallinity, pasting, rheological, and morphological properties of corn resistant starch

Abstract

In this research, corn resistant starch (CRS) was mixed with four kinds of soluble dietary fibers (chitosan, flaxseed gum, xanthan gum, and konjac gum). The pasting and rheological properties, microstructure, and X-ray diffraction spectrum of the mixed system were investigated by rapid viscosity analyzer (RVA), rheometer, scanning electron microscopy (SEM), and X-ray diffractometer (XRD). The pasting curves showed that the addition of chitosan could reduce the viscosity of CRS paste, while the flaxseed gum, xanthan gum and konjac gum increased the viscosity. All complex systems had shear thinning properties in the rheological steady flow experiments. Soluble dietary fibers significantly increased the value of viscosity coefficient (K) of the CRS, however, the value of flow characteristic index (n) was decreased with increasing concentration of soluble dietary fibers. Soluble dietary fibers addition resulted in higher storage modulus and loss modulus (G′ and G″) of CRS paste, as well as giving rise to high viscoelasticity. SEM confirmed that the addition of soluble dietary fibers made the starch granules more easily aggregated in the mixed systems. X-ray diffraction spectrum analysis showed that the addition of soluble dietary fibers did not change the B and V type crystalline pattern of CRS, and both the concentrations and types of soluble dietary fibers had significant effects on the crystallinity of mixed systems. This study reported four mixtures with CRS and provided useful information for functional food.