Cereal Chem 60:429 - 432. | VIEW
Composition of Acid- and Alkali-Extracted Barley Proteins as Revealed by Isoelectric Focusing.
A. M. El-Negoumy, C. W. Newman, and B. R. Moss. Copyright 1983 by the American Association of Cereal Chemists, Inc.
Barley cultivars Carlesberg II and its mutant Carlesberg/Riso-56, and Bomi and its mutant Bomi/Riso 1508 were extracted with 0.05M NaOH or 0.05M acetic acid to remove glutelin after sequential extraction of the albumin, globulin, and hordein fractions. Samples of these cultivars were also extracted with deionized water at pH 2, 4, 6, 8, 10, and 11. Albumin and globulin were isolated from a sample of Lenta barley, both before and after dialysis in deionized water, to remove natural salts. An isoelectric focusing technique more suitable for barley proteins was used to examine the extracted proteins. The glutelin extracted with acetic acid represented only 1.1% of the total protein and appeared, on the basis of isoelectric points, to be composed of albumin and globulin components. However, this may not be the true composition, because proteins with similar isoelectric points may differ in their other chemical and physical properties. Glutelin extracted with NaOH represented about 25% of the total protein and differed completely in electrofocusing composition from that extracted by acetic acid. The proteins extracted with deionized water at pH 2-8 resembled those extracted by acetic acid, whereas those extracted at pH 10 and 11 contained all protein fractions including glutelin. These results may indicate that the acetic acid extract consisted mainly of the remnants of albumin plus globulin left in the residue after albumin, globulin, and hordein were extracted. Removal of natural salts from a sample of Lenta flour by dialysis gave an albumin fraction much less contaminated with globulin and ensured more complete recovery of the globulin fraction.