Preparation and Structure Analysis of Noncrystalline Granular Starch

Noncrystalline granular (NCG) starch is a peculiar form of starch. The granules have granular shape but no crystalline structure. It is a middle state between native semi-crystal structure and paste. The conception of NCG starch was presented and its preparation methods for native maize starch were explored. Cross-linking by chloroepoxy propane was adopted as the chemical method while ethanol treatment was adopted as the physical method. Cross bonds and ethanol were both able to protect starch granules from swelling while thermal treatment was able to destroy crystalline structure of the granules. The structure of granule was observed by polarization microscope and scanning electron microscopy (SEM). Change from crystalline to noncrystalline structure was confirmed by X-ray diffraction (XRD). It indicated that preparation of NCG starch with the physical method was better than chemical method. The detailed conditions were: maize starch (40%, w/w) was slurried in 50%-ethanol, underwent thermal treatment at 85 degrees C for 2 minutes, washed with anhydrous ethanol (2000 ml), and freeze dried.