Optimization of Process Variables to Develop Teff-Amaranth Based Extrudates
Creators: name: Berhe, Aregay
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2014

description: Response Surface Methodology was adopted to study the effect of barrel temperature (A), screw speed (B), feed moisture content (C) and blend ratio (D) to optimize the proximate composition, physical properties(expansion ratio, bulk density and specific length), functional properties(WAI and WSI) and sensory quality attributes during extrusion process to develop teff-amaranth based extrudates using twin screw co-rotating extruder. Kuncho and red teff grains with voucher numbers DZ-C1-387 and DZ-01-99, respectively and three amaranth varieties (white, pale-white and black amaranth) were studied for proximate composition, mineral content, phytochemical content and functional properties. The moisture contents for DZ-C1-387 and DZ-01-99 were11.12 and 12.27%, respectively. The proximate compositions of DZ-C1-387 were 12.46(protein), 2.82(fat), 2.82(ash), 2.45(crude fiber) and 68.64% (total CHO), respectively, and the proximate composition of DZ-01-99 were 10.19, 2.42, 2.42, 2.51and 70.12% for crude protein, crude fat, ash, crude fiber and total CHO respectively. The energy value of DZ-C1- 387(349.78kcal/100g) was significantly (p&lt;0.05) higher than the energy value of DZ-01-99 (343.02kcal/100g). Among the three amaranth varieties, moisture (10.24), protein (17.85), fat (7.00), ash (2.70), crude fiber (6.86) and total CHO (55.35%), respectively were the proximate compositions for white amaranth. The proximate compositions of pale-white amaranth were11.50, 14.15, 6.30, 5.40, 2.20 and 60.45% for moisture, crude protein, crude fat, crude fiber, ash, total CHO, respectively. The moisture, crude protein, crude fat, crude fiber, ash and total CHO content of the black amaranth were 10.89, 15.30, 6.50, 5.75, 2.40 and 59.16%, respectively. The energy value of white amaranth (354.80kcal/100g) was significantly (p&lt;0.05) higher than the energy values of pale white amaranth (351.10kcal/100g) and black amaranth (351.34kcal/100g), respectively. 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 extruded products were evaluated for their chemical composition, mineral content, physical properties, functional properties and sensory quality attributes. The optimum extrudate which was obtained at 1300c (barrel temperature), 140rpm (screw speed), 15% (feed moisture content) and 15% amaranth in the feed had 13.70% protein, 3.53% fat, 2.98% fiber, 2.66% ash and 70.27% total CHO and 19.52, 170.47, 5.08, 386.54, 176.98mg/100gm for Fe, Ca, Zn, P and Mg and 33.72% phytates and complete reduction of tannins was observed in this study. The maximum expansion ratio (3.0789), maximum WAI (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 WSI (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 teff- amaranth based extrudate development and process optimization studies. Keywords: Teff, Amaranth, Extrusion, Extrudates, Optimization, Response Surface Methodology