F. N. Hepburn, W. K. Calhoun, and W. B. Bradley. Copyright 1960 by the American Association of Cereal Chemists, Inc.
The eighteen commonly occurring amino acids were determined by microbiological analysis in two blends of hard red spring and hard red winter wheats and in each of the final products produced by commercial milling. The summation of amino acid values obtained for the separate products, weighted by the proportion of the whole wheat represented in each product, yielded total values in good agreement with the results determined for the wheat. Changes in the relative proportions of the amino acids showed the same trends in both sets of samples. Less lysine, glycine, arginine, alanine, and aspartic acid was found in the flour fractions and more in the offals than in the wheat proteins. Conversely, more proline, glutamic acid, and phenylalanine was found in the flour proteins and less in the offals than was found in the wheats. The proportions of the remaining amino acids were much less affected by milling. The uniformity of amino acid concentrations within the flour fractions explains the previous observation that the amino acid distribution of flour proteins was independent of the degree of separation of the flour. It is postulated that the consistency of amino acid distribution in bread flour protein may be related to the selection and blending of wheats.