Protein Quality and Acceptability of Sorghum Flour Supplemented with Defatted Groundnut Flour as Influenced by Traditional Processing

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Date
2015-06-16
Authors
Ellhag,Mardia Eltahir
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Publisher
University of Khartoum
Abstract
Sorghum flour (SF) was supplemented with defatted groundnut flour (DGF); 15, 20 and 25% composite flours, their protein content, fractions and digestibility were determined. Supplementation significantly (P<0.05) increased protein content, fractions (albumin plus globulin) and the in vitro protein digestibility, whereas prolamin, glutelins and insoluble proteins significantly (P<0.05) decreased as a result of supplementation. The in vitro protein digestibility was 49.3, 64.6, 56.8, 60.1 and 62.5% for (SF), (GDF), and 15, 20 and 25% composite flours, respectively. Sorghum flour and the selected 20% composite flour(according to acceptability) were naturally fermented for 36 hr. Fermentation was found to significantly (P<0.05) increase the protein content, albumin plus globulin, G2 and G3-glutelin fractions and the in vitro protein digestibility, whereas it significantly (P<0.05) decreased prolamin and G1-glutelin fractions. The insoluble protein fluctuated throughout the fermentation time. The fermentation of 20% composite flour was found to increase protein content from 20.1 at 0 hr to 24.3 at 36 hr, albumin plus globulin from 64.7 at 0 hr to 70.2 at 36 hr, prolamin decreased from 15.0 at 0 hr to 11.6% at 36 hr, G1-glutelin decreased from 12.1 at 0 hr to 9.4 at 36 hr, G2-glutelin increased from 1.5 at 0 hr to 2.6% at 36 hr, G3-glutelin from 9.2 to 10.1% and insoluble protein from 0.4 at 0 hr to 0.8% at 36 hr of fermentation. The in vitro protein digestibility of 20% composite flour was 49.3, 75.2, 65.1, 74.0 and 68.2% for 0, 8, 16, 24 and 32 hr of fermentation, respectively. Cooking was found to reduce the nutritive value of sorghum and the 20% composite flour significantly (P<0.05) the protein content of the former from 8.8 to 7.4% and of the latter from 20.1 to 19.3%; also it reduced the albumin plus globulin from 16.7 to 8.3% in sorghum and from 64.7 to 58.6% in 20% composite flour. The in vitro protein digestibility was reduced due to cooking from 49.3 to 42.1% in (SF) and from 60.1 to 56.4% in 20% composite flour. Fermented 20% composite flour was cooked and the effect of cooking after fermentation was detected; fermentation was found to reduce the negative effect of cooking on the nutritive value. The albumin plus globulin fraction was significantly (P<0.05) increased from 58.6% in cooked 20% composite flour to 60.2, 63.6, 65.1, 61.2 and 64.5% in 0, 8, 16, 24 and 32 hr fermented cooked. The prolamin decreased from12.0 in cooked 20% composite flour to 10.9% in 32 hr fermented cooked. The in vitro protein digestibility of 20% composite flour was decreased from 56.4% in cooked sample to 44.4, 70.2, 62.9, 67.3 and 65.2% in 0, 8, 16, 24 and 32 hr fermented cooked samples, respectively. The effect of supplementation and/or fermentation on the acceptability of sorghum flour was studied; the 25% composite flour was markedly accepTable than the 15% composite flour in terms of odor, taste and colour, however, the 20% composite flour was the most accepTable in odor, taste, colour and general acceptability than the 15 and 25% composite flour (25% was less accepTable in terms of colour). The 20% selected flour was fermented and tested for acceptability against the unfermented composite flour, fermentation leveled up the acceptability especially in case of taste and odor.
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116 Pages
Keywords
protein;sorghum;flour;oil;Cooking;sudan;food;chemical composition;china;united states;dura
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