Protein isolates rich in methionine from the edible dry bean (Phaseolus vulgaris L.)

Several extraction and fractionation schemes were investigated for their ability to fractionate edible dry bean seed proteins into classes of variable methionine content. Isoelectric precipitation or dialysis from a protein solution of low ionic strength resulted in protein isolates having methionine content equal to or lower than the average seed methionine. A protein isolate rich in methionine was obtained by the adjustment of a high ionic strength protein solution at pH 4.1. This methodology excluded the major storage seed proteins, which are known for their low methionine content.