Evaluation of nutrient content in red kidney beans, amaranth leaves, sweet potato roots and carrots cultivated in Rwanda

Abstract

No data exist on the nutrient composition of some important Rwandan staples. The aim of this study was to evaluate the nutrient content of red kidney beans, sweet potato roots, amaranth leaves and carrot roots. About 6 kg of each raw material were cleaned and conditioned prior to mechanical drying, ground and sieved [60-mesh] into flour and then subjected to quantitative analysis for proximate content, energy, calcium (Ca), iron (Fe), zinc (Zn), vitamin A and vitamin C. Proximate composition determination was done using Near Infrared Spectroscopy (NIRS), carbohydrates were determined by difference, energy was calculated, mineral analysis was done by Atomic Absorption Spectroscopy (AAS) and vitamin analysis was performed by High Performance Liquid Chromatography (HPLC) methods. The results showed that red kidney beans, sweet potato roots, amaranth leaves and carrots contain 21.48, 6.66, 29.46 and 13.8% of protein; 2.58, 1.68, 7.89 and 2.08% of fat; 60.86, 79.13, 19.29 and 57.38% of carbohydrate; 2.33, 2.68, 8.98 and 9.63% of fiber; 8.82, 8.74, 10.08 and 8.88% of moisture content; 3.94, 1.11, 24.30 and 5.16% of ash; 357.2, 363.7, 284.0, 322.9 kcal/100 g of energy; and 146.4, 182.7, 26,290 and 1,247 mg/kg of calcium, respectively. Red kidney beans, amaranth leaves and carrots contained 8.54, 30.48, and 15.55 mg/kg of zinc; and 21.36, 219.1 and 8.81 mg/kg of iron, respectively. Zinc and iron were, however, not detected in sweet potato samples analysed. Red kidney beans, sweet potato roots, amaranth leaves and carrot contained 768.0, 10,880, 399.4, and 6,413 IU/100 g of vitamin A; and 2.67, 30.99, 330.3 and 6.76 mg/100g of vitamin C, respectively. In conclusion, the staples analysed contained appreciable amounts of nutrients and could be used to overcome malnutrition and allow dietary diversity. It could be recommended to prepare a Rwandan food composition database in order to improve awareness on local grown crops’ quality.