Cereal Chem 46:614 - 620.  |  VIEW ARTICLE
Determination of Free Lysine and Methionine in Amino Acid-Fortified Wheat.

R. E. Ferrel, D. A. Fellers, and A. D. Shepherd. Copyright 1969 by the American Association of Cereal Chemists, Inc. 

Nutritional enhancement of cereal proteins by fortifying with limiting amino acids appears to be both simple and practical. A rapid and simple method for determining lysine and methionine added to wheat is reported. Finely ground fortified material is extracted with dilute hydrochloric acid. Methionine content of an aliquot of the extract is determined colorimetrically with nitroferricyanide, and total ninhydrin reactants are determined colorimetrically on a second aliquot. Lysine content is calculated from the total ninhydrin color and the methionine content. The effects of pH on the ninhydrin color and of added glycine on reducing interference in the nitroferricyanide method are discussed.