Optimization of technological parameters of casein hydrolysis

Milk proteins are valuable raw materials for obtaining protein hydrolysates and active peptides formed during hydrolysis. Various proteolytic enzymes and bacteria are most often used for hydrolysis. Important parameters for regulating the degree of protein hydrolysis are duration, temperature of hydrolysis and concentration of a biological agent. The aim of the study was to establish optimum parameters for casein hydrolysis with chymotrypsin and bacterial starter of acidophilus bacillus. A three-factor experiment was used to determine optimum conditions for the hydrolysis process. Three factors were varied during the experiment: hydrolysis time (from 6 to 26 h) with a step of 10 h; temperature (from 32 to 42 °C) with a step of 5 °C; starter amount (from 0.5 to 1.5 %) with a step of 0.5 %. The dependent variable was the degree of hydrolysis. The content of total nitrogen in casein was determined by the Kjeldahl method, and that of amine nitrogen was determined by formol titration. The influence of independent variables on the dependent variable was analyzed using MathCAD, where response surfaces were also constructed. For the obtained multiple regression equations, the authors determined the reliability of the equation by the determination coefficient (R2) and Fisher’s criterion (Fkr), and the statistical significance of the parameters of the multiple regression equation by the Student’s criterion (t). Two regression equations were obtained for the process of casein hydrolysis with chymotrypsin and bacterial starter. Determination coefficients were established, confirming the high significance of the models. Response surfaces were constructed showing the dependence of the hydrolysis degree on the hydrolysis parameters. The optimum parameters of hydrolysis with the enzyme chymotrypsin and acidophilus starter were established. For example, when using chymotrypsin with a hydrolysis duration of 21.99 h, a temperature of 43.3 °C, and an enzyme amount of 0.02 %, the hydrolysis degree will be 28.6 % and when using acidophilus starter with a hydrolysis duration of 31.1 h, a temperature of 35.8 °C, and an amount of starter of 1.5 %, the hydrolysis degree will be 17.33 %.) Thus, the results of the multifactorial experiment made it possible to establish the optimum hydrolysis parameters for obtaining casein hydrolysates with chymotrypsin and acidophilus starter.

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