Evaluation of suitability of substituting wheat flour with sweet potato and tiger nut flours in bread making

The study was carried out to assess the nutritional quality and palatability of bread after partially substituting wheat flour (WF) with sweet potato (SF) and tiger nut (TF) flours. Sweet potato (yellow fleshed) and tiger nut flours were used to substitute wheat flour at 5, 10, 15 and 20% level each. The bread quality of each of these composite flours evaluated on the basis of their nutritional quality, physical properties and acceptability by consumers. The findings indicate slight decrease in the protein content of the bread samples with increasing sweet potato and tiger nut supplementation (6.97% in 100% wheat flour to 3.80% in 20% level of substitution) while crude fibre content increased with increased sweet potato and tiger nut substitution (2.29% in 100% WF to 2.80% in 20% substitution) but there was no significant change (<0.05) in the ash and fat contents. Carbohydrate which was the major component ranged from 73.47 – 79.42%. Findings on the study on the functional properties showed that water absorption capacity increases with increase in the level of sweet potato and tiger nut substitution (0.54g/ml in 100% WF to 1.12g/ml in 20% level of substitution). The loaf volume and specific volume of the bread samples decreased significantly with increase in the level of substitution with sweet potato and tiger nut and it ranged from 320cm3 (in 100% wheat flour) – 216cm3 (in 20% substitution) and 1.55cm3/g (in 100% wheat flour) to 0.98cm3/g (in 20% level of substitution) respectively. Bread from 100% wheat flour scored the highest in all the sensory properties evaluated. There was no significant difference between the control and bread from 5% level of substitution in terms of all the sensory parameters evaluated however bread from higher levels of substitution varied significantly with the control. All the bread samples were acceptable in all the parameters evaluated except bread from 20% level of substitution. The study concludes the potential health and sensory benefits of partial substitution of sweet potato and tiger nut to wheat flour in bread making through improved fibre content, improved taste and to promote sweet potato and tiger nut utilization.