Variability in Phytochemicals, Á-Galactosides, Sucrose Composition and <i>in vitro</i> Protein Digestibility of Common Bean (<i>Phaseolus vulgaris</i> L.) Varieties

Abstract

The variability in the phytochemicals, á-galactosides, the sucrose composition and the in-vitro protein digestibility of common bean varieties released from research centres were investigated. Concentrations for á- galactosides (raffinose and stachyose) and phytochemicals (lectins, saponins, phytic acid, protease inhibitors and tannins) varied significantly (P < 0.05) amongst the common bean varieties. Mean values for raffinose, stachyose, total á-galactosides, sucrose, trypsin inhibitors, tannins, phytic acid, saponin and lectins were 3.14 mg g-1, 14.86 mg g-1, 17.99 mg g-1, 24.22 mg g-1, 20.68 TUIx103 g-1, 17.44 mg catechin equivalent g-1, 20.54 mg g-1, 1.01 g 100 g- 1 and 4.75 g kg-1 PHA based on dry weight basis respectively. In vitro protein digestibility varied significantly (P <0.05) among the bean varieties and had a positive significant correlation with sucrose content and negative correlations with trypsin inhibitors, tannins, lectins, á-galactosides and saponins. The correlation matrix indicated that variability in á-galactosides, the protein digestibility, the phytochemical composition and the sucrose contents of beans existed. In addition, a protective role against diseases was correlated with the amount of phytochemicals quantified in the bean samples. Amongst the studied bean varieties, Roba has the potential to be used as a raw material in the food-processing industry owing to its higher in vitro protein digestibility, lower phytochemicals composition and other beneficial nutritional parameters.

Keywords: Phaseolus vulgaris; Protein Digestibility; Á-Galactosides; Phytochemicals; Sucrose

East African Journal of Sciences Vol. 2 (1) 2008: pp. 45-54