Quality properties of bread from blends of wheat flour and sweet orange seed protein concentrate

Abstract

The study investigated the effect of substitution of wheat flour with sweet orange seed protein concentrate on the quality of bread. Protein concentrate, obtained from sweet orange (Citrus sinensis) seeds was used to substitute 5, 10, 15, 20 and 30% of wheat flour in breads. The flours were assessed for functional and pasting properties while the breads were evaluated for proximate composition, physical and sensory properties. Sweet orange seed protein concentrates and wheat flour had bulk densities of 0.45 g/cm3 and 0.72 g/cm3, respectively while those of the flour blends ranged from 0.61 - 0.70 g/cm3. Wheat flour had lower contents of moisture, crude fiber, ash, protein, and fat than the protein concentrate, which had lower carbohydrate content. Sweet orange seed protein concentrate had highest foaming capacity, water and oil absorption capacities but lowest least gelation concentration among all the flours. The peak viscosities of protein concentrate and wheat flour were 886.21 RVU and 675.20 RVU, respectively. The peak, trough, breakdown, final and setback viscosities of the flour blends decreased while peak time and pasting temperature increased with increase in the substitution of wheat flour with protein concentrate. In length, loaf weight, height, oven spring, loaf volume, specific volume and weight loss, the 100% wheat flour breads had 12.03 cm, 172.60 g, 5.35 cm, 0.62 cm, 471.50 cm3, 2.73 cm3/g and 10.42%, respectively while breads containing 5% sweet orange seed protein concentrate had 12.02 cm, 171.40 g, 4.60 cm, 0.61 cm, 350.50 cm3, 2.04 cm3/g and 9.28 %, respectively. The proximate composition of the breads containing 5 and 10% sweet orange seed protein concentrate were improved over that of wheat flour bread. The sensory attributes of the breads decreased with increased level of sweet orange seed protein concentrate in the breads. However, the breads containing 5 and 10% sweet orange seed protein concentrate were not significantly (p>0.05) different from the 100% wheat bread in colour. Thus, the incorporation of up to 10% sweet orange seed protein concentrate in wheat flour improved the functional properties of the flour blends and the qualities of the bread. Adoption of this approach will address malnutrition, wastages and environmental pollution (caused by the discard of orange seeds).