Optimization of Process Variables to Develop Teff-Amaranth Based Extrudates

Response Surface Methodology was adopted to study the effect of barrel temperature, screw speed, feed moisture content and blend ratio to optimize the physical properties (expansion ratio, bulk density and specific length) and functional properties (water absorption index and water solubility index) during extrusion process to develop teff-amaranth based extrudates using twin screw co-rotating extruder. Kuncho teff grains with voucher numbers DZ-C1-387 which was harvested in DebreZeit Agricultural Research Center in 2011/12 and white amaranth which was collected from Konso commercial market were used for production the extrudates. On the basis of extruded product quality, the extrusion process variables were feed moisture (12, 18, and 24%), teff - amaranth blend ratio (90:10, 85:15 and 80:20%), barrel temperature (110, 130 and 150?C) and screw speed (120, 140 and 160 rpm) through a die of opening about 9.00mm. the physical properties, functional properties of all the extruded products were evaluated. The maximum expansion ratio (3.0789), maximum water absorption index (8.728g/g) and minimum bulk density (0.1614g/cm3) values of the extrudates were observed at 130 0C, 140 rpm, 15% feed moisture content and 85:15 blend ratio. The the maximum specific length (3.6193cm/g) was obtained at 150 0C, 160 rpm, 15% feed moisture content and 80:20 blend ratio and the maximum water solubility index (22.217%) was obtained at 150 0C, 120 rpm, 15 feed moisture content and 80:20 blend ratio. In this study, promising results were obtained for the development of teff- amaranth based extrudates and process optimization studies.