Production of ACE Inhibitory Peptides from Trypsin Hydrolyzing Whey Protein

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.