Effect of Bambara Groundnut Flour (Vigna subterranea (L.) Verdc.) Supplementation on Chemical, Physical, Nutritional and Sensory Evaluation of Wheat Bread

Abstract

Bambara groundnut (Vigna subterrenea (L) Verdc) is a major source of vegetable protein in sub-Saharan Africa. And the aim of this study was to enhance the nutritional value of wheat bread through the addition of bambara groundnut flour to wheat four. For this, bambara groundnut seeds were soaked in tap water, manually decorticated, sun dried and milled into fine flour. Proximate analysis of flours of de-hulled bambara groundnut and wheat were conducted. Flour of de-hulled bambara groundnut was used for bread supplementation in ratios of 5, 10 and 15%. Rheological properties of the control flour and wheat flour supplemented with 10% of de-hulled bambara groundnut flour were conducted. The total area and dough development time increased. However, water absorption, stability and extensibility respectively decreased, from 71.3; 8.5; 190 in the control flour to 71.0; 5.5; 180 in the 10% supplemented flour. The increases in the resistance to extension and proportional number from 260 to 280 and 1.37 to 1.56, respectively resulted in stiff dough. The most important effect of wheat bread supplementation was the improvement of protein quantity from 13.74 +/- 0.02% for the control bread to 15.49 +/- 0.02, 17.00 +/- 0.05 and 18.98 +/- 0.02% for the 5, 10 and 15% blending ratios, respectively. The in-vitro protein digestibility progressively increased from 84.33 +/- 0.03 in the control bread to 85.42 +/- 0.04, 86.57 +/- 0.04 and 87.64 +/- 0.03 in breads containing 5, 10 and 15% bambara groundnut flour. The sensory attributes of different types of bread showed that, a significant difference was observed in texture, colour and overall acceptability. However, the panelists gave higher score for 10% de-hulled bambara groundnut flour bread than bread made from other blends. The loaf weights, loaf volume and specific volume increased. However, while the loaf weight increased with addition of 15% de-hulled bambara groundnut flour, both of loaf volume and specific volume decreased. Nutritional value of wheat bread can be enhanced by the addition of de-hulled bambara groundnut flour at a level of up to 10%.