Optimization of Process Variables to Develop Teff-Amaranth Based Extrudates
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Date
2014-06
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Addis Ababa University
Abstract
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<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<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
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Keywords
Teff, Amaranth, Extrusion, Extrudates, Optimization, Response Surface Methodology