Nutritional and Functional Implications of Yellow Yam-Soybean Composite Flour for Food Formulation: Evidence from Kogi State, Nigeria

Yellow yam (Dioscorea cayenensis) is widely consumed in West Africa but remains nutritionally limited by its low protein and essential amino acid content. Soybean (Glycine max), a legume rich in high-quality protein and functional nutrients, offers a strategic fortification option. This study assessed the proximate composition, functional properties and amino-acid profile of yellow yam–soybean composite flours formulated to enhance nutritional value and support food-based approaches to malnutrition reduction. Yellow yam and soybean flours were produced using standard procedures and blended at ratios of 100:0, 90:10, 80:20, 70:30 and 60:40 (YYF: SBF). Soybean fortification substantially improved nutritional quality: protein increased from 10.18% to 23.11%, while TEAA and TAA rose from 25.60 to 34.84 mg/100 g and 68.76 to 94.72 mg/100 g, respectively. Functional properties such as water and oil absorption, solubility, emulsifying activity and foaming capacity increased, whereas swelling power decreased. Yellow yam–soybean composite flour provides enhanced nutritional density, superior amino-acid balance, and improved functional behaviour, indicating strong potential for developing nutrient-dense foods in yam-dependent regions.