STUDIES ON SOME ENGINEERING PROPERTIES OF ACHA (DIGITARIA EXILIS) STARCH

This study investigated some engineering properties of acha starch with the view of promoting its usage in food processing. Starch was extracted from acha grain following a documented procedure with little modification and a portion was modified. The physiochemical, rheology and thermal properties were investigated following standard procedures. The moisture contents ranged from 2.85 to 10.64%. Loose and packed bulk densities, the least gelation concentration, density ratio and porosity ranged between 0.32 to 0.51 g/ml, 0.39 to 0.66 g/ml, 8 to 16% (w/v), 75.21 to 82.19%, and 17.80 to 24.78%, respectively. Similarly, the Carr index had a range of 21.28 to 33.00% and Hausner ratio ranged from 1.22 to 1.33, indicating the starch samples had a fair (native starch), very poor (modified starch) and good (potato starch) flow properties, using Carr standard. The amylose, amylopectin and amylose-amylopectin ratio contents obtained range from 24.07 to 29.77%, 70.23 to 75.93% and 0.32 to 0.42%, respectively. Also, the thermal properties of the samples measured using Differential Scanning Calorimeter (DSC) ranged between 72.7 to 83.6 ⁰C, 87.38 to 106.4 ⁰C, 89.6 to 106.2 ⁰C and 6.27 to 33.5 ⁰C for onset temperature, peak temperature, end temperature and temperature range, respectively. The viscosity values obtained ranged from 408.65 – 665.2 and 417.9 – 447.1 mPa.s for native and modified acha starch, respectively. Hence, this study provides engineering data in relation to process design, control and bulk handling with a view to extending the usage of acha starch samples in the food processing industry.