Cereal Chem 44:183 - 192.  |  VIEW ARTICLE
Solubility and Ultracentrifugal Studies on Soybean Globulins.

A. M. Nash and W. J. Wolf. Copyright 1967 by the American Association of Cereal Chemists, Inc. 

Solubilities of laboratory and commercial preparations of soybean globulins were measured in 0.5 ionic strength, pH 7.6, potassium phosphate-sodium chloride buffer. Measurements with and without 0.01M 2- mercaptoethanol in the buffer gave an estimate of insoluble disulfide polymers. Compositions of the soluble proteins were determined by ultracentrifugation.Five laboratory samples of soybean globulins prepared by isoelectric precipitation and freeze-drying had solubilities of 37-73% in buffer and 66-78% in buffer containing 2-mercaptoethanol. Five commercial globulin samples in the isoelectric form had solubilities of 6-59% in buffer and 10-66% when 2-mercaptoethanol was present. Seven commercial soybean proteinate samples had solubilities ranging from 6-81% in buffer as compared to 13-83% in buffer containing 2- mercaptoethanol.Solubilities of all samples were increased by 2-mercaptoethanol, but wide variations occurred. Ultracentrifugal analysis also showed large variations in the compositions of different samples. Some commercial preparations closely resembled laboratory samples in solubilities and ultracentrifugal compositions. Other commercial samples had low protein solubilities and appeared extensively modified by the isolation process. Samples of lecithinated proteinate, pepsin-hydrolyzed protein, and alkali-modified protein were included for comparison.