Effect of processing on Nutritional and Anti nutritional Compositions, and Functional Properties of Selected Sorghum Varieties Grown in Ethiopia

Abiye, Kifle (2011) Effect of processing on Nutritional and Anti nutritional Compositions, and Functional Properties of Selected Sorghum Varieties Grown in Ethiopia. Masters thesis, Addis Ababa University.

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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.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	Sorghum, Grain processing, chemical composition, Functional properties
Subjects:	S Agriculture > S Agriculture (General) S Agriculture > SB Plant culture T Technology > T Technology (General)
Divisions:	Africana
Depositing User:	Selom Ghislain
Date Deposited:	18 Jun 2018 11:32
Last Modified:	18 Jun 2018 11:32
URI:	http://thesisbank.jhia.ac.ke/id/eprint/4325

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