Development of Bread from Different Protein Isolates, Sweet potatoes (<i>Lam Ipomea batata</i>) and Wheat Flour Blends

Bread is a universally accepted and convenient food produced majorly from wheat flour. However, Nigeria faces a challenge in wheat production, relying heavily on imports thereby incurring a substantial annual expenditure in foreign exchange. Efforts have been made to promote the use of different composite flours from locally grown crops to substitute wheat flour for bread production. This study investigated the potential of developing nutritious and healthy bread from blends of wheat (W), Orange fleshed sweet potato (OSFP), Cream fleshed sweet potato (CSFP), Soy protein isolate (SI) and Whey isolate (WI). Freshly harvested OSFP and CFSP were procured locally. D-Optimal mixture design of design expert software was used to obtain the optimum blending ratios of wheat flour (75%): sweet potato(25%) and thereafter the protein isolates SI and WI were added in three different proportions (2%, 4% and 6%) the control was made with wheat: sweet potato (75%: 25%) without protein isolate. The flour blend were used to bake bread. The ash, protein, fat and carbohydrate contents of the flour blends ranged from 1.63 to 1.77%, 8.56 to 8.83%, 1.53 to 1.62%, and 65.03 to 74.03%, respectively while the ash, protein, fat and carbohydrate contents of the bread ranged from 1.54 to 1.80%, 14.80 to 27.49% and 3.04 to 3.62%, 41.59 to 54.14% respectively.. The penetrometer readings indicated values ranging from 1.53 to 2.63 10th mm and 136.66 to 243.67 10th mm, respectively. The specific volume, oven spring and loaf weight of the bread samples ranged from 1.68 to 3.50cm3/g, 0.30 to 1.50cm and 137.13 to 159.63g respectively. The sensory evaluation result indicated that the value obtained for the overall acceptability ranged from 7.34 and 8.75. Bread samples with 4% protein isolate were recommended to be relatively more acceptable. In conclusion, the adding of protein isolates to the blend of wheat and sweet potato has increased the protein content also produced bread with acceptable sensory properties. This can be recommended for bakers in utilizing OFSP/CFSP to substitute wheat in bread making. This will minimize cost and maximize profit in bread making.