Abstract
Acha (Digitaria exilis) starch was chemically modified using sodium hypochlorite (3.5% active chlorine) as oxidative agent. The physicochemical properties of the native acha starch and oxidized derivative were investigated. Oxidation improved the water and oil absorption capacity of the native acha starch and also the emulsion capacity was significantly improved. The bulk density, foam capacity and solubility reduced upon oxidation. The granule morphologies investigated using scanning electron microscopy showed significant difference in the ratio of crystalline and amorphous regions. However, oxidation of native acha starch did not affect the shape, appearance and structural arrangement of the starch granules. The granules were polygonal in shape with size range of 6 to 8.57 µm. The infra spectra showed additional band at 3600 cm-1 for the oxidized derivative indicating hydroxyl group stretching vibration of carboxylic acid. This indicates that the oxidation of native acha starch was successfully carried out. Improved physicochemical properties impacted upon oxidative modification is quite desirable in impacting greater stability and less retrogradation and seneresis of the native acha starch. Thus, oxidized acha starch will find suitable applications in food, pharmaceutical, paper and textile industries as good dispersants, emulsifying agent, surface sizing, adhensive, disintegrants, excipients and preparation of biopolymer based flocculants.
Key words: Modified starch, starch oxidation, physicochemical properties, scanning electron microscopy, starch granules.
