Contributions to the Amino Acid Composition of Protein Fractions of Wheat Flours

Abstract

The amino acid composition of wheat flours of different quality and their protein fractions separated by an acetic acid fractionation method were determined. Flours milled from the following wheats were used: Jubilejnaja 50, Partizanka, GK-F2, Rana 1, Száva. Three protein fractions were separated from the flours: proteins soluble in 1 M NaCl, proteins soluble in 0,1 M acetic acid, and proteins insoluble in 0,1 M acetic acid. The determination of the amino acid composition — except tryptophan — was carried out from the acidic hydrolysate of protein fractions and of the starting flours by means of a Chinoin Lys 75 type automated amino acid analyzer,, Some characteristic differences were found in the amino acid composition of protein fractions in comparison with each other and with the composition of the starting flours. The salt-soluble protein fractions show the most considerable differences by their higher asparatic acid, glycine, alanine, leucine, lysine, arginine, and lower glutamic acid and proline values. The amino acid compositions of the acetic acid-soluble and acetic acid-insoluble protein fractions show more similarity, that is the content of basic amino acids is very low, while glutamic acid and proline are present in very high amounts in both. In the latter ones the proportion of glycine is also relatively higher. Similar characteristic differences were not found among the same types of protein fractions of different flours.