4.5. Determination of the Protein Concentrate Amino Acid Composition

To study the amino acid composition of proteins, a method was used based on the decomposition of the objects of study under the action of acids (concentrated hydrochloric and sulfuric acids) and inorganic alkali into free forms of amino acids, their further separation, and quantitative determination of the latter on a capillary electrophoresis system Capel-105/105M (Lumex, St. Petersburg, Russia) using the M-04-38-2009 technique, which is based on the extraction of acids from the test sample with distilled water, separation, and quantitative determination of components by capillary electrophoresis with indirect detection at a wavelength of 190 nm [27]. An L-amino acids kit LAA-21 by Lumex (Lumex, St. Petersburg, Russia) was used as standard samples. The protein hydrolysis process in the presence of acid (H⁺) is shown in Scheme 1.