Chemical and Physicochemical Changes in Field Bean and Soybean Proteins Texturized by Extrusion

The solubility of extruded field bean and soybean protein in a pH = 6.9 buffer was less than 22%. Extensive solubilization could be obtained in buffers containing sodium dodecyl sulfate (SDS) and SDS plus dithiothreitol (DTT). The cysteine + cystine content decreased by 8.5% after extrusion of field bean protein, but remained constant with soybean protein. The content of all other amino acids was not changed; 1.4% (soybean) to 3.2% (field bean) of the lysine residues became chemically unavailable after extrusion. There was no significant formation of lysinoalanine or lanthionine. Electrophoretic patterns of initial and extruded proteins (SDS plus DTT solubilized) were very similar except for the appearance of a low mobility aggregate in extruded field bean protein.