Val bean (Lablab purpureus L.) proteins: composition and biochemical properties

Val bean (Lablab purpureus L.) proteins were fractionated using the Osborne protein fractionation scheme and biochemically characterized. The seed flour contained 302 g kg^?1 protein (micro‐Kjeldahl N × 6.25) on a dry weight basis. Albumin, globulin, prolamin, and glutelin accounted for 22.8%, 45.1%, 1.8% and 30.3%, respectively, of the total soluble seed proteins. Among the solvents tested, 0.1 mol L^?1 aqueous NaOH was the most effective protein solubilizer. Isoelectric focusing indicated the seed proteins to be predominantly acidic (pI range was ～4–7). Val globulin is a glycoprotein composed of at least three polypeptides in the molecular mass range 51–64 kDa. Albumin fraction had the highest trypsin inhibitory activity, while the globulin fraction registered the highest hemagglutinating activity. Sulfur amino acids were the first limiting amino acids in the total seed proteins. The proportion of essential to total [E/T(%)] amino acids for the bean flour was 36.97%. Among the protein fractions, glutelin fraction had the highest E/T (42.86%) followed by albumin (41.57%), globulin (39.87%), and prolamin (39.15%). Native globulin, although resistant to pepsin, was effectively digested in vitro upon moist heat (100 °C, 30 min) denaturation. Copyright © 2007 Society of Chemical Industry