Nutritional quality and functional properties of finger millet, sweet potato, and soybean composite flour as affected by blending ratios

Despite their low nutritional values, cereals are the main raw materials that are used for the development of different food products. This study aimed to develop nutrient-rich flour blended from orange-fleshed sweet potato, finger millet, and soybean. The experiment was conducted to optimize the blending ratio of composite flours. Thirteen formulations of composite flours were generated using a mixture design with varying ratios of finger millet (45–55%), OFSP (30–40%), and soybean (10–20%). The composite flours' physical, functional, and nutritional properties were evaluated. The data were analyzed using Design Expert software version 13. The statistical analysis showed significant (P < 0.05) variations in protein, ash, carbohydrate, beta-carotene, bulk density, water absorption index, and water solubility index of the composite flours. Graphical optimization was used to determine the optimum values for each variable, resulting in 16% protein, 3.31% ash, 64.27% carbohydrate, 7.908mg/100g beta-carotene, 0.7g/ml bulk density, 2.78g/g WAI, and 15.95% WSI, in a blend of 47.46% finger millet, 34.54% orange-fleshed sweet potato, and 17.99% soybean flours. This study demonstrated that incorporating orange-fleshed sweet potato and soybean flour into composite flours significantly increased their nutritional value. These findings suggest that optimizing the blending ratio of composite flours can lead to nutrient-rich flour development with desirable nutritional and functional properties.