Abstract
The chemical composition, amylose content and physio-chemical properties of dioscorea starch (Dioscorea abyssinica, Fam. Dioscoreaceae) from Ethiopia have been investigated. The proximate composition of the starch on dry weight basis was found to be 0.1% ash, 0.5% protein, 1.0% fat and 98.4% starch. The amylose content was 29.7%. Scanning electron microscopy (SEM) showed rounded granules. Particle size analysis revealed granule size distribution with a mean particle size of 29.2 μm. X-ray diffraction study showed a pattern that is typical of B-type with a distinctive maximum peak at around 17° 2 T. The moisture sorption pattern, the swelling power and the solubility values were determined and found to be lower than potato starch. Brabender viscosity curves of 6% starch paste showed a peak viscosity of 781 BU. The breakdown and retrogradation of dioscorea starch were 25 and 501 BU, respectively. DSC parameters of starch-water mixture (1:2) exhibited an onset temperature (To) of 64.2°C, a peak temperature (Tp) of 68.2°C and an endset temperature (Te) of 74.8°C. The enthalpy of gelatinization (ΔH) was 19.2 mJmg−1.
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