Preparation and Characterization of Homogeneous Blend of Dietary Fiber and Starch Based on Ionic Liquids

Abstract

In this study, a homogeneous blend of starch and dietary fiber (DF), which contained both water‐soluble and water‐insoluble compositions, is prepared in ionic liquids. The morphology and structure of the regenerated blend are studied using a scanning electron microscope (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). It is found that the morphological structures of both original starch and DF are destroyed, and a homogeneous morphological structure is formed for the blend during the dissolution‐regeneration process in ionic liquids. Though no new chemical combination is observed from the infrared spectrum of the regenerated blend, the shift of absorption peaks appeared due to the destruction of the hydrogen bond during the dissolution of ionic liquids. The XRD results showed that the regenerated blend showed a disordered structure which is different from the orderly crystalline structure of original starch and DF. The disordered structure may result in the reduction of thermal stability. Among three ionic liquids 1‐allyl‐3‐methylimidazole chloride ([AMIM]Cl), 1‐ethyl‐3‐methylimidazole chloride ([EMIM]Cl), and 1‐ethyl‐3‐methylimidazole acetate ([EMIM]OAc), [EMIM]Cl has the best solubility to the blend and also has the most disruptive to the native structure of starch and DF, correspondingly.