PROXIMATE COMPOSITION, ANTINUTRIENT PROFILE, MINERAL CONTENT AND PHYTOCHEMICAL PROPERTIES OF PIGEON PEA (CAJANUS CAJAN), BLACK TURTLE BEAN (PHASEOLUS VULGARIS), RED KIDNEY BEAN (PHASEOLUS VULGARIS L.) AND AFRICAN BLACK BEAN (VIGNA UNGUICULATA) SEEDS.

Summary

Legumes are inexpensive sources of protein, vitamins, fiber, complex carbohydrates and essential minerals, and occupy a special place in human diet, particularly in developing countries. However, their nutritional quality is adversely affected by the presence of antinutrients which limit the proper metabolism of valuable nutrients. This study evaluated the proximate composition, antinutrient profile, mineral content and phytochemical properties of pigeon pea, black turtle bean, red kidney bean and African black bean seeds. Milled seed samples were analysed for proximate composition using standard AOAC methods, antinutrients by colorimetric and titrimetric methods, minerals by atomic absorption spectrophotometry and phytochemicals by standard qualitative and quantitative methods. Data were expressed as mean ± SD and compared by one-way ANOVA at p<0.05. The result revealed that Crude protein content was highest in red kidney beans (18.87%) and African black beans (18.00%), while black turtle beans had the lowest (12.05%). Ash content was highest in African black beans (8.88%) and lowest in pigeon peas (6.88%). Alkaloid content was highest in African black beans (2.84%) and lowest in pigeon peas (1.58%). Flavonoid content was highest in red kidney beans (4.17%) and least in black turtle beans (2.47%). Iron level was highest in black turtle beans (2.67 mg/kg) and lowest in African black beans (1.06 mg/kg). Copper was highest in pigeon peas (1.03 mg/kg). Manganese and selenium were highest in black turtle beans (1.50 mg/kg and 7.19 mg/kg respectively). In conclusion, the four legumes are rich in protein, minerals and phytochemicals, but their antinutrient contents suggest that processing methods such as soaking and boiling should be employed to reduce antinutrient levels before consumption.

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