By Nkesiga, Jackson
Extruded snacks were produced from flour blends of yellow maize, soybean, carrot and amaranth
leaf, in order to generate nutrient dense snacks for children and adults. Flour samples of wheat,
yellow maize, soybean, carrot and amaranth leaf were produced by cleaning, drying, milling and
sieving prior to chemical analysis. Amaranth leaf flour was incorporated into yellow maize and
soybean (70:30) composite flour at 0, 5, 10, 15 and 20 % replacement levels, while yellow
maize-soybean-carrot flour blend formulated at 65:30:5 ratio as well as wheat flour (100 %),
served as controls. Baking ingredients (sugar, salt, baking fat, baking powder and vanilla) were
added to the composite flour blends as well as to wheat flour, to produce extruded snacks in a
single screw extruder, before drying in an oven at 60 oC for 30 minutes. The extruded snacks
were subjected to chemical, functional properties, microbiological and sensory evaluation using
standard methods. Based on the preliminary study, the best ratio 60:30:10 (yellow maize:
soybean: amaranth leaf flour) was selected for optimization using full factorial design. The flour
samples had high ranges of protein (11.69 - 48.19 %), ash (0.99 - 15.98 %), fat (1.89 - 18.5 %),
crude fiber (3.06 - 17.14 %), carbohydrate (15.06 - 67.53 %) and energy (267.13 - 419.44
kcal/100g) as well as vitamins such as β-carotene (96.45 - 3471.12), thiamine (0.47 - 1.11
mg/100g), riboflavin (0.30 - 3.91 mg/100g), vitamin C (10.22 - 29.46 mg/100g) and vitamin E
(1.38 - 1.71 mg/100g) and minerals such as calcium (89.58 - 164.99 mg/100g), iron (2.02 - 15.27
mg/100g), zinc (1.75 - 5.43 mg/100g) and magnesium (8.98 - 87.73 mg/100g). Incorporation of
amaranth leaf and soybean flour significantly (p < 0.05) increased the protein content from 17.88
to 21.67 % and energy from 349.72 to 360.07 kcal/100g. Amaranth leaf flour incorporation
significantly (p < 0.05) increased the mineral and vitamin contents of the extrudates. Addition of
5 % amaranth leaf flour significantly (p < 0.05) increased protein, mineral and vitamin contents
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of extruded snacks compared to the controls. Extrusion cooking and drying processes
significantly (p < 0.05) reduced the antinutritional factors of the extruded snacks by 98.5 %,
compared to the raw flour. The microbial load which was very low, ranged from 1.08 to 9.4 x
101 cfu/g for bacteria count, 0.00 to 3 x 101 cfu/g for mould count, while coliform was not
detected in all extruded snack samples. Addition of amaranth leaf and carrot powder significantly
(p < 0.05) reduced expansion ratio, water absorption capacity and significantly (p < 0.05)
increased the bulk density, pH and oil absorption capacity of the extrudates. The most acceptable
snack was the wheat flour (control) followed by the sample incorporated 5 % carrot powder,
while acceptability of other extruded snacks decreased with increasing addition of amaranth leaf
flour. The optimum dough water content, entry barrel temperature, centre barrel temperature and
end barrel temperature established were 103 ml, 70 oC, 120 oC and 130 oC, respectively.