APPLICATION OF BAMBARA GROUNDNUT (Vigna subterranean L. Verdc) SEED PROTEINS IN THE DEVELOPMENT OF BISCUIT; AND KINETICS OF ITS STARCH DIGESTION

Abstract

Complementary feeding using commercially available foods may be unaffordable in low income settings. Hence, research into available traditional crops as low-cost alternatives to the conventional complementary foods is of necessity. The aim of this study was to determine the potential of bambara groundnut, an underutilised legume for use both as flour and protein isolate in biscuit production to address Protein Energy Malnutrition (PEM). Fifteen response surface methodology (RSM) runs were evaluated from combination of wheat flour (WF), bambara groundnut flour (BF) and bambara protein isolate (BPI). Based on the crude protein and functional properties these ratios were selected WF: BF (85.0:15.0%, 76.2:23.8% and 52.5:47.5%) and labeled as WBF1, WBF2, WBF3, respectively with WF: BPI (85.0:15.0%, 76.2:23.8% and 52.5:47.5%) as WBPI1, WBPI2 and WBPI3 for blends of wheat flour and bambara protein isolate respectively. The proximate, mineral, amino acid composition, functional and antinutritional properties of the composite flour blends and biscuits were determined. The molecular weight distribution of the proteins of the composite flours, with sodium dodecyl sulphate poly acrylamide gel electrophoresis (SDS-PAGE), In-vitro bambara starch digestion and kinetics of degradation were determined. The nutritional qualities of the biscuits were evaluated using rat feeding studies with determination of some haematological, enzyme activities and histopathological analyses. The biscuits were analysed for physical quality parameters and acceptability by sensory evaluation. Data were analysed using one way analysis of variance (ANOVA) and significance at P<0.05. The wheat-bambara groundnut flour, wheat-bambara groundnut protein isolate and biscuits contained (g/100g) moisture (9.43-9.63), (1.64-3.59), (6.70-7.60), (4.00-5.70), total ash (0.79-1.76), (2.83-3.37), (1.00-170), (2.50-2.80) and crude fat (5.16-6.92), (0.84-1.03), (6.40-7.80), (4.69-6.30) respectively. While the crude protein, wheat-bambara groundnut flour (14.41-21.67), wheat- bambara groundnut protein isolate (32.42-61.10) and biscuits (15.30-20.10) (26.20-46.20) g/100g were recorded respectively. The carbohydrate content for wheat-bambara flour (62.47-66.75) g/100g, wheat-bambara protein isolate flour (31.56-61.21) g/100g and biscuits (63.10-67.00), (40.50-5750) g/100g. The mineral composition (mg/100g): Sodium ranged from (442.06 to 960.36) for wheat-bambara composite flour, biscuit (3.12-4.77), Calcium ranged from (94.33-494.88) for wheat-bambara composite flour, biscuit (2.08-3.82) and Potassium ranged from (41.00-500.00) and biscuit (1.10- 2.20) respectively. Among the trace metals, Copper ranged between for wheat-bambara composite flour (14.80-35.11), biscuit (0.04– 0.06) and Manganese ranged between for wheat-bambara composite flour (8.00-26.03), biscuit (0.21 -0.31) were high in the composite flour and low in the biscuit samples. Lead was not detected in both the flour samples and the biscuit. The calculated mineral ratios Na/K of the composite flour (0.24-0.41) and biscuits (0.58- 0.92) respectively while the Ca/P ratio for wheat-bambara composite flour (1.07-2.42) and biscuit (2.00- 2.47). The Ca/P ratios in the composite flour and biscuit samples were greater than FAO (2003) recommendation (>1.0), this will help to increase the absorption of calcium in the small intestine. The oil and water absorption properties of the flour and protein isolate were generally high and it implies that the samples will be able to absorb oil and water well. In tested composite flour and biscuit produced, antinutritional compounds like phytates and trypsin inhibitor activities in the composite flour samples were greater than those of the biscuit samples. Electophoretic identification explicated that legume flour and protein isolates polypeptide bands fall within the range of 27.2-81.31 kDa. It is deduced that bambara groundnut had better protein isolates recovery and yield thus suitable for the preparation of protein enriched food formulations. In vitro starch digestibility of the composite flour had high catalytic efficiency between 1.70-4.49. The inhibition constant of the composite flour was high in the range 0.82-2.32 and the half life ranged between 77-115.5. The limiting and most abundant amino acids (g/100g) were methionine in wheat-bambara composite flour (32.73-90.24) and biscuit (58.64-131.36) and arginine in wheat-bambara composite flour (149.50-429.00) and biscuit (98.37-307.50). The essential amino acid index (EAAI) of wheat-bambara composite flour ranged between (57.16- 66.35) and (37.06 – 76.49) for biscuit. The Protein Efficiency Ratio (PER) of wheat-bambara composite flour and biscuit (2.40-2.70) and (1.70 – 3.05) respectively. The Biological Value (BV) ranged between (50.60- 60.63) for wheat-bambara composite flour and (47.17–66.99) for biscuit. Hence, the essential amino acids in the composite flour and biscuit may adequately support growth and development in infants, children and adults. No significant pathological changes were observed in liver and kidney of rats fed with WBPI3 and Casein. Rats fed WBPI3 were within normal range and compared very well with those in casein group, with no signs of leison, indicating the safety of the biscuit in fed animals. The biscuit from the composite flours were generally liked slightly by the panelists. In conclusion, these findings imply that the WBPI3 (52.5:47.5%) composite flour sample and biscuit among the other levels of the flour and biscuit will be safe to consume and useful as potential composite biscuit formulation.