**2.2. Determination of chemical composition**

Indicators of the chemical composition of protein products were determined by the methods of state standards of the Russian Federation and generally accepted methods. The mass fraction of moisture was determined in accordance with GOST 13586.5-85; ash content—GOST 10847-74; mass fraction of fat—according to the method of Soxhlet in the apparatus of the firm "Buchi"—GOST 29033-91, the mass fraction of protein—in the automated Kjeldahl system of the firm "Buchi"—GOST 10846-91, fiber—according to Gennesberg and Shtoman—GOST 31675-2012. Carbohydrates were calculated as the difference between 100% and the sum of the mass fraction of protein, fat, ash, and fiber.

#### **2.3. Determination of the amino acid composition of proteins**

A liquid chromatograph from Hitachi (Japan) was used in a mode with a sulfonated styrene-divinylbenzene copolymer and a step gradient of sodium citrate buffer solutions with increasing pH and molarity. The data were processed in an online system "MultiChrome 1.52" for Windows 98. A sample of 3–5 mg sample was placed in a glass ampoule, 300 μl of a mixture of concentrated hydrochloric acid and trifluoroacetic acid (2, 1) with 0.1% 2-mercaptoethanol was added. The sample was frozen in liquid nitrogen, evacuated and hydrolyzed at 155°C for 1 h. The hydrolyzable mixture was evaporated on a rotary evaporator (Centrivap Concentrator Labconco, USA). To the residue, 0.1N HCl was added and centrifuged for 5 min at 800 g on a Microfuge 22R centrifuge (Beckman-Coulter, USA).
