Enzymatic Hydrolysis of Soy Protein

Abstract

Soy continues to be one of the top sources of vegetable protein. Structurally modified soy proteins and processed products are used as part of functional foods. Enzymatic hydrolysates of food proteins have different degrees of hydrolysis and functional profiles, hence the constant search for the optimal hydrolysis parameters. The present research objective was to design a two-stage enzymatic conversion process of soy protein using mathematical methods, as well as to evaluate the antioxidant properties of the hydrolysate in laboratory conditions. Soy protein isolate was tested to define the maximal value of the hydrolysis degree. It underwent a series of two-factor experiments in the presence of pepsin and trypsin. The study focused on the hydrolysis time and the enzyme-substrate ratio. The results were optimized using the response surface methodology in MathCad 15. The total antioxidant activity of the hydrolysate during hydrolysis was determined on a Tsvet-Yauza-01-AA chromatograph using the amperometric method. For the pepsin test, the processing time was 7 h and the enzyme-to-substrate ratio was 1:22. For the trypsin test, the time was 7 h and the ratio was 1:30. The mathematical modeling revealed the following optimal parameters. The first stage involved hydrolysis with pepsin for 5 h at an enzyme-to-substrate ratio of 1:20; the second stage involved hydrolysis with trypsin for 3 h at an enzyme-to-substrate ratio of 1:19. The resulting hydrolysate demonstrated 88% hydrolysis. The highest summary antioxidant activity was registered after 5 h of hydrolysis and amounted to about 250 mg/100 mL. The resulting enzymatic hydrolysate of soy protein can be used as a food component or an antioxidant feed additive. The obtained peptides can immobilize essential microelements, e.g., Zn, I, and Se, as well as produce polyvalent complexes. Further studies will be aimed at the residual antigenicity of the hydrolysate and other functional indicators.