Abstract:

The effects of pH, temperature, enzyme to substrate ratio, substrate concentration and hydrolysis time on the hydrolysis degree of whey protein were studied using single factor test. In the following, a Box-Behnken experiment design involving 15 experiments of 3 factors (i.e., pH, temperature, enzyme to substrate ratio) at 3 levels coupled with response surface method was employed to optimize the hydrolysis process. The optimum hydrolysis conditions were as follows: pH 7.50, temperature 45.0 ℃, enzyme to substrate ratio 0.059 (E/S=1:16.92, m/m), substrate concentration 6% and hydrolysis time 150 min. Under such conditions, the degree of hydrolysis was 18.38%, and the ACE inhibition rate was 63.23% after hydrolysis for 8 h. The ACE peptides obtained from the hydorlysis process were further fractionated with ultrafiltration, Sephadex G-25 and Sephadex G-10, and exhibited 75.95% of ACE inhibition.

Key words: whey protein hydrolysis, ACE inhibitory peptide, purification