Cereal Chem 66:478-482   |  VIEW ARTICLE

Protein Composition of a High-Protein Barley Flour and Barley Grain.

R. Linko, A. Lapvetelainen, P. Laakso, and H. Kallio. Copyright 1989 by the American Association of Cereal Chemists, Inc. 

The hot air-dried, proteinaceous by-product from a barley starch pilot plant was compared with the raw material of the process, 10% dehulled barley grain. The by-product, high-protein barley flour, has been used for feeding pigs, cows, and sheep. The proportions of four protein fractions, isolated according to their solubility, and the nonprotein nitrogen content were evaluated. The polypeptide distribution of the protein fractions was observed by vertical sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by densitometric scanning. The amino acids of the fractions were determined by gas chromatography of their pentafluoropropionyl-2-propyl esters. The protein content was approximately three times greater in the barley protein flour tha n in barley grain. The most abundant protein fraction was that of alkali-soluble "glutelins" (45%) in the protein flour and that of alcohol-soluble "prolamins" (35%) in barley grain. During processing, the proportion of prolamins and water- and salt-soluble "albumins" + "globulins" decreased, as the proportion of glutelins increased. In the barley protein flour, 80% of the salt-soluble nitrogen compounds was nonprotein nitrogen. The most remarkable differences between the amino acid compositions of the protein flour and its raw material were detected in glutelin fractions. The sum of the essential amino acids determined was 6-21% lower in all protein fractions of protein flour compared with that of the barley grain. The polypeptide distribution differed most in the albumin and globulin fractions.