Effect of processing on Nutritional and Anti nutritional Compositions, and Functional Properties of Selected Sorghum Varieties Grown in Ethiopia
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Date
2011-06
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Addis Ababa University
Abstract
There are brown and red colored bird resistant and whitish colored bird sensitive sorghum varieties in
Ethiopia. Thus, the bird resistant sorghum varieties commonly provide higher yield in areas where there
is higher population of birds. However, there is a hypothesis that colored grains are rich in anti-nutrient
tannins. The main objective of the present investigation was therefore to improve the sensory
acceptability and reduce ant-nutritional composition of the bird resistant grains which maintaining the
bird resistant characteristics. Accordingly, the seeds were decorticated by hardening the endosperm
using hydrothermal processing method and to evaluate changes during decortications. Standard methods
were used to analyze proximate composition, anti-nutritional contents (Tannins, Phytate, Alkaloid and
Polyphenols), minerals and functional properties of four sorghum varieties namely; Seredo and Abba
melko and Teshale and Wogere. The findings showed that the yield of decorticated head grain, broken
and seed coat were 75.7-77.9%, 0.9-4.32% and 19.8-21.2% respectively. The decorticated grains of the
respective varieties had significantly lower level of protein, fat, fiber, ash, minerals (Zn, Fe, Mg and Cu)
and bulk density and significantly higher carbohydrate (P<0.05), water absorption capacity and water
solubility index as compared to the undecorticated grains. Decortication has also reduced the level of
phytate from 78-82%, Tannins 62-92%, Total Alkaloids 9-86% and Total polyphenols 59-100% of the
grains respectively. Even if decortications reduces titrable acidity, fermentation increase the titrable
acidity by 33.3% and also fermentation was found to cause a gradual reduction in a pH with time which
had significant role in flavor/taste and critical importance with regard to the shelf-life and safety of food.
Through fermentation at 0hrs to 48hrs on average the pH was drop from 6.61 to 5.53. However, Tannin
content of the sorghum would have no significant effect on fermentation processes. High popping
capacity of the selected sorghum varieties was obtained for unprocessed grains as compared to processed
and tempered grains. Sensory acceptability showed like slightly to moderately for all unleavened breads
prepared from processed and unprocessed grain flours. In conclusion decortications has significantly
reduced anti-nutritional factors and slightly lowered macronutrients and minerals except carbohydrate.
Therefore, it is suggested to maximize growing of the bird resistant varieties by farmers and apply
appropriate food technologies that increase the bioavailability of their nutrients.
Key words: Sorghum; Grain processing; chemical composition; Functional properties
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Keywords
Sorghum; Grain processing; chemical composition; Functional properties