Optimisation of Nutrient, Anti-nutrient, and antioxidant Properties of Flour Blend Derived from Orange-fleshed Sweet Potato-Cowpea-Moringa Leaves

Abstract

Background: Orange-fleshed sweet potato (OFSP), Cowpea Leaves (CL), and Moringa Leaves (ML) are bioactive compounds-rich foods that may be used in functional foods production. The objective of this study was to develop functional composite flour, rich in bioactive compounds from the blends of fermented Orange-fleshed Sweet Potato, Cowpea leaves, and Moringa leaves. The effect of fermentation on the nutritional, functional, antioxidant, and antinutrient properties of the flour was investigated, as well as the optimisation of the flour blends using Response Surface Methodology (RSM). Aim: This study aims to produce a composite flour from Orange-fleshed sweet potato (OFSP), cowpea, and moringa leaves to obtain a product rich in bioactive compounds that can serve as a panacea for certain degenerative diseases. Methods: Samples of OFSP, CL, and ML were fermented for 24 h, dried, and milled into flours, and their proximate, mineral, antioxidant, and antinutrient properties were determined using standard AOAC methods. Statistical design and analysis were carried out using an optimal mixture design of response surface methodology. Optimal Mixture Model of Response Surface Methodology (RSM) (Design Expert 16.0) was used for the experimental design and statistical analyses. The means were separated by the New Duncan Multiple Range Test (NDMRT). A statistical package (SPSS) was also used for some statistical analyses. Significance was set at p < 0.05. The alpha-amylase and alpha-glucosidase of the selected optimised flour blends were evaluated. Results: Fermentation led to a substantial increase in protein content of cowpea leaves (22.78%) and moringa leaves (23.69%). Reduction in the antinutritional factors such as tannins, saponins, glycosides, and alkaloids was also observed. Increased antioxidant activity, including DPPH scavenging and Fe²⁺ was observed in fermented leaves but not in OFSP. The proximate composition of the sample range is crude protein (13.91–17.00%), crude fibre (7.05–8.56%), and carbohydrate (51.85–65.98%). Samples FBG (88.85% OFSP, 7.50% CL, 3.65% ML)   and FB6 (91.2613% OFSP, 7.50% CL, 1.23866% ML) had the highest α-Amylase and α-glucosidase Inhibition, and this positions them as potential blends in the management of diabetes. FRAP values as indicators of reducing power were highest in FBG (4.95), followed by FBA (4.78), FB8 (4.64 mg (Vit. C)/g), and FB6 (4.18 mg (Vit. C)/g), as indicated by the phenolic content of the blends. Chelation ability of Fe²⁺ was strongest in FB8 (52.34%), followed by FBA (49.54%), FB6 (45.41%), and FBG (42.62%). Conclusions: The optimised samples provide nutritional and bioactive-rich samples, which will be potential raw materials as functional foods.  The findings revealed the potential of local crops with untapped potential to combat malnutrition, degenerative diseases, secret hunger, and sustainable agriculture through producing high-value-added products.