Iisolation and physicochemical characterization of cassava starches obtained from different regions of ethiopia

Abstract

The chemical composition, amylose content and physicochemical properties of cassava (Manihot esculenta Crantz., Fam. Euphorbiaceae) starches obtained from different regions of Ethiopia were investigated. The proximate composition of the starches on dry weight basis were found to be 0.001 - 0.01% protein, 0.08 - 0.11% fat, 0.03 - 0.1% ash, and 85.7% - 87.5% starch. The amylose contents of cassava starches from Gamo Gofa, Illubabor and Wollega were estimated to be 16.1%, 21.1% and 18.9%, respectively. Scanning electron microscopy (SEM) showed spherical granules. Particle size analysis revealed granule size distribution with a mean particle size of 12.71 μm (Gamo Gofa) 14.34 μm (Illubabor) and 11.70 μm (Wollega). X-ray diffraction study of the starch displayed A-type pattern with a distinctive maximum peak at around 17.0° 2θ. The true average density of the starch was found to be 1.497 g/ml. Brabender viscosity of 6% starch paste showed peak viscosities of 198.5 BU (Gamo Gofa), 224.0 BU (Illubabor) and 208.0 BU (Wollega). Differential scanning calorimeter (DSC) parameters of native starch-water mixture (1:2) exhibited an onset temperature (To), a peak temperature (Tp) and an endset temperature (Te) of 60.19, 65.80, 71.53 (Gamo Gofa), 55.93, 60.80, 66.61 (Illubabor), and 58.29, 64.70, 72.47 (Wollega), with a corresponding gelatinization enthalpy (ΔH) of 21.04, 17.05, and 22.34 mJmg-1, respectively.

Keywords: cassava starch, amylose content, X-ray diffraction, Brabender viscosity, gelatinization