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 raw materials used the most for developing different food products. This study aimed to enhance the nutrient content of finger millet flour by developing 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 using standard protocols and 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. The result indicated that increasing the percentage of OFSP and soybean flour enhanced the protein and beta-carotene content from 9.6 to 17.9% and 6.3 to 9.015 mg/100 g respectively. The optimum values for each variable using graphical optimization resulted in 16% protein, 3.31% ash, 64.27% carbohydrate, 7.908 mg/100 g beta-carotene, 0.7 g/ml bulk density, 2.78 g/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 showed that incorporating orange-fleshed sweet potato and soybean flour into composite flours significantly increases their nutritional value. Hence, optimizing the blending ratio of composite flours can lead to nutrient-rich flour development with desirable nutritional and functional properties.