The digestibility of proteins in red kidney bean (Phaseolus vulgaris L.) was examined by in vitro pepsin assay. A 20-kDa polypeptide that remained highly stable after heat processing was identified as a basic subunit of legumin. The results of a monobromobimane (mBBr) labeling test implied that this protein contained rigid intramolecular disulfide bonds, which might contribute to pepsin resistance.
