SOME PHYSICOCHEMICAL PROPERTIES OF DIOSCOREA STARCH FROM ETHIOPIA

The chemical composition, amylose content and physio-chemical properti es of dioscorea starch (Dioscorea abyssinica, Pam. Dioscoreaceae) from Ethiopia have been investigated. The proximate composition of the sta rch 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 elec tron microscopy (SEM) showed rounded granules. Particle size analysis revealed granule size distribution with a mean particle size of 29.2 m u m. X-ray diffraction study showed a pattern that is typical of B-typ e with a distinctive maximum peak at around 17 degrees 2 Theta. The mo isture sorption pattern, the swelling power and the solubility values were determined and found to be lower than potato starch. Brabender vi scosity curves of 6 % starch paste showed a peak viscosity of 781 BU. The breakdown and retrogradation of dioscorea starch were 25 and 501 B U, respectively. DSC parameters of starch-watts mixture (1:2) exhibite d an onset temperature (T-o) of 64.2 degrees C, a peak temperature (T- p) of 68.2 degrees C and an endset temperature (T-e) of 74.8 degrees C . The enthalpy of gelatinization (Delta H) was 19.2 mJmg(-1).