Nutrient composition, protein quality and antinutritional factors of some varieties of dry beans (Phaseolus vulgaris) grown in Burundi

Four varieties of dry beans (Phaseolus vulgaris) grown in four different areas of Burundi were analyzed for moisture, protein, fat, ash, mineral (potassium, calcium, magnesium, iron, copper, zinc, and phosphorus), essential amino acids (isoleucine, leucine, lysine, methionine, phenylalanine, threonine, valine) and antinutritional factors (raffinose oligosaccharide, trypsin inhibitor, hemagglutinin, tannin and phytic acid) contents. In-vitro digestibility of dry bean proteins was also evaluated. The concentrations observed for the proximate composition. protein quality, and antinutritional factors varied significantly (P < 0.05) among the 13 'variety-locality' combinations investigated in this study. Mean values for moisture, protein, fat, ash, and carbohydrate were 9.19%, 22.26%, 1.01%, 4.47%, and 72.33% respectively. They were 525, 55.2, 38.2, 7.63, 0.92, 7.33 and 456 mg/100 g for potassium, calcium, magnesium, iron, copper, zinc and phosphorus, respectively; and 7.35, 14.49, 13.49, 1.59, 9.85, 9.08 and 9.11 mg/g for isoleucine, leucine, lysine, methionine, phenylalanine, threonine and valine, respectively. Finally values for raffinose, stachyose, trypsin inhibitor, hemagglutinin, tannin and phytic acid were respectively 2.20 mg/g, 18.40 mg/g, 15.02 TUI X 10-3/g, 2.15 HU X 10-3/mg, 14.99 mg catechin equivalent/g and 16.50 mg/g. The levels obtained for different nutrients (except for some minerals) and antinutrients were in agreement with those found in dry beans in other areas of the world. Protein digestibility ranged from 67.47% (Calima variety from Kirimiro) to 71.99% (A410 variety from Imbo). These values were comparable to those obtained in other countries. Statistical analyses of data confirmed that nutrient content, protein digestibility and undesirable factors were influenced by both variety and locality. Relationships between some dry bean nutrients and between antinutritional factors and protein digestibility were also observed.