Cereal Chem 43:80 - 93.  |  VIEW ARTICLE

Carbohydrate Content of Soybean Proteins.

W. J. Wolf, D. A. Sly, and W. F. Kwolek. Copyright 1966 by the American Association of Cereal Chemists, Inc. 

Several fractions of soybean proteins were analyzed with phenol-sulfuric acid to determine the range of carbohydrate content of soybean proteins. Protein fractions were prepared by a variety of purification techniques, including isoelectric precipitation, ammonium sulfate precipitation, alcohol washing, and chromatography on hydroxylapatite. A final purification common to all samples was exhaustive dialysis against distilled water, followed by freeze-drying. All protein preparations gave a positive test for carbohydrates with phenol-sulfuric acid. Carbohydrate analyses expressed as percent glucose included: water-extractable proteins, 1.6-2.0; isoelectrically precipitated globulins, 1. 5-2.3; whey proteins, 2.8-4.2; glycinin, 1.5-1.9; cold-insoluble fraction, 0.3-0.5; and purified 11S component, 0.2.Effluents of soybean proteins chromatographed on hydroxylapatite columns were analyzed with phenol-sulfuric acid. Although carbohydrates were eluted with all the proteins present in the water-extractable mixture, definite fractions were indicated. The first carbohydrate fraction was non-dialyzable, was eluted as a sharp peak slightly ahead of the first protein fraction, and occurred largely in whey upon isoelectric precipitation of the globulins. Four or more carbohydrate fractions were eluted with the other water-extractable protein components.