Effects of extrusion and traditional processing methods on antinutrients and in vitro digestibility of protein and starch in faba and kidney beans

Comparative effects of extrusion cooking and conventional processing methods on protein content and reduction of antinutritional factor (phytic acid, condensed tannins, polyphenols, trypsin, chymotrypsin, α-amylase inhibitors and haemagglutinating activity) levels in Vicia faba and Phaseolus vulgaris seeds were studied. In vitro protein and starch digestibilities were assessed. P. vulgaris seeds showed highest levels of condensed tannins, chymotrypsin and α-amylase inhibitory activities and haemagglutinating activity. Dehulling significantly increased protein content and greatly reduced condensed tannin and polyphenol levels in both legumes. Extrusion was the best method to abolish trypsin, chymotrypsin, α-amylase inhibitors and haemagglutinating activity without modifying protein content. Furthermore, this thermal treatment was most effective in improving protein and starch digestibilities when compared with dehulling, soaking and germination.