Nutritional and functional properties of Bambara groundnut and Moringa oleifera leaf protein complex in a ready-to-use therapeutic food (RUTF)

Abstract

This research aimed to produce Bambara groundnut-Moringa oleifera leaf protein complex (BAMOLP), evaluate its physical, nutritional, and functional properties to establish suitability as a functional ingredient in the production of ready-to-use therapeutic food. Protein isolates were extracted from Bambara groundnut flour (BGNF) and Moringa oleifera leaf powder (MOLP). The alkaline/isoelectric extraction method was used for the extraction of protein from BGNF, while heat treatment was used for protein extraction from MOLP. Phase behaviour of Bambara groundnut protein isolate (BGNPI) and Moringa oleifera protein isolate (MOLPI) was investigated to study their interaction and stability in a water system. BGNPI and MOLPI were varied at two levels each based on a 22 factorial experimental design augmented with centre points comprising of BGNPI (1, 5, 9% w/v) and MOLPI (5 to 4.5% w/v) as independent variables in 100% distilled water. Compositions obtained from 22 factorial experimental design were analysed for stability, particle size, and syneresis by using Turbiscan MA 2000, a zetasizer Malvern Instruments (NanoZS) and visual observation respectively. Eleven (11) compositions were established, and the effects were determined on the equilibrium backscattering (BS) flux as the stability indicator for the protein mixture. The BS profiles obtained from the Turbiscan stability analysis by using Turbiscan MA 2000 revealed Sedimentation, creaming, and flocculation were the destabilisation mechanism of the protein mixture. Experimental data obtained from stability index, syneresis (%), and particle size were used to determine the most stable composition of the protein mixtures. A protein mixture with 9% BGNPI and 2% MOLPI was established as the optimal mix for the production of BAMOLP. An investigation of physical, functional, and nutritional characteristics of Bambara groundnut protein isolates (BGNPI), Moringa oleifera leaf protein isolates (MOLPI), and their protein complex (BAMOLP) was carried out. The protein isolates and their complex were non-newtonian and pseudoplastic. The oil absorption capacity (OAC) of BGNPI, MOLPI, and BAMOLP was 2.26, 0.89, and 0.95 g/g respectively while the water absorption capacity (WAC) for BGNPI, MOLPI, and BAMOLP were 1.31, 1.5, and 1.22 g/g. The WAC and swelling capacity of the BGNPI, MOLPI, and BAMOLP increased with temperature from 60 to 90oC. The foaming capacity was pH dependant. BAMOLP exhibited a higher emulsifying capacity and stability than BGNPI and MOLPI. The protein, fat, ash, carbohydrate, and moisture content of the protein isolates and complex ranged from 39.42 to 63.51%, 2.19 to 11.52%, 1.60 to 7.09%, 24.07 to 51.29%, and 2.61 to 9.57% respectively and significantly (p < 0.05) differed from one another. The results show that BAMOLP exhibits a better amino acid profile, rheological and chemical properties than its precursors: BGNPI and MOLPI. Furthermore, a ready-to-use therapeutic food (RUTF) using BAMOLP, oats, millets, egusi, MOLP, and other ingredients were simulated using the mixture preparation procedure in Superpro Designer. BAMOnut snack bars were assessed for physicochemical, nutritional, and sensory properties. Three ready-to-use therapeutic bars produced were BAMOnut-OB3 (BAMOnut Bar enriched with oats and 3% BAMOLP, BAMOnut-MB2 (BAMOnut Bar enriched with millets and 2% BAMOLP), and BAMOnut-OMB5 (BAMOnut Bar enriched with oats, millets, and 5% BAMOLP). The BAMOnut snack bars were dark-yellowish, and less saturated since their chroma ranged from 11.70 to 20.83. Eleven mineral components (sodium, magnesium, phosphorous, potassium, calcium, iron, nickel, copper, zinc, selenium, iodine) were identified in the snack bars. There was no significant difference in the texture of the BAMOnut snack bars but the formulation with a higher concentration of MOLP has a lower sensory rating in appearance, colour, aroma, taste, and overall acceptability. Moisture (4.9%), protein (14.1%), fat (19.3%), CHO (59.7%), and energy (468.6 Kcal/100 g), of BAMOnut-OB3, compares favourably with the requirement for RUTF (2.5, 13-16, 26-36, 41-58%, for moisture, protein, carbohydrate, respectively and and 520-550 Kcal/100 g for energy). Local raw materials namely, Bambara groundnut and Moringa oleifera can be successfully used in the production of an alternative RUTF for severely acutely malnourished children and also as nutritious snacks for adults.