Protein quality and antinutritional factors in wild and cultivated species of Vigna spp.

The nutritional quality of wild and cultivated species of Vigna has been evaluated. Wild species showed significantly higher protein content (P less than 0.01), antitryptic activity (P less than 0.005) and tannin content (P less than 0.025) and significantly lower protein digestibility (P less than 0.005). No significant differences were found with regard to protein quality, measured as chemical score corrected by the digestibility; sulphur amino acids turned out to be limiting in both groups. In addition no correlations were found between sulphur amino acids and protein levels, or between sulphur amino acid and trypsin inhibitor levels. Selected lines showed an improvement from the nutritional point of view linked to lower antitryptic factors and tannin content, which may give rise to a decreased resistance to pests. For all the properties considered, whether physical or biochemical, wild samples presented wider variations and the types considered most primitive were those that differed most from the cultivated ones, whose properties were altogether more consistent. In vitro protein digestibility turned out to be a useful parameter in evaluating wild and improved samples.