COMBINED EFFECT OF ULTRASOUND AND ENZYMATIC TREATMENTS ON PRODUCTION OF ACE INHIBITORY PEPTIDES FROM WHEAT GERM PROTEIN

Inhibition of angiotensin I-converting enzyme (ACE) activity is effective in reducing blood pressure. Wheat germ protein, an important by-product of the flour milling industry, is rich in ACE inhibitory peptides. In this article, wheat germ protein was pretreated with ultrasound ranging from 200 to 1800 W before hydrolysis, and response surface methodology (RSM) was employed to optimize enzymatic hydrolysis conditions for the preparation of ACE inhibitory peptides. The results showed that ultrasonic pretreatment increased the ACE inhibitory activity of the peptides released from wheat germ protein. When wheat germ protein was pretreated with ultrasound at 600 W for 10 min, the ACE inhibitory activity was increased by 32.14% over the control. Single-factor experiments displayed that the change in ACE inhibitory activity was not consistent with the degree of hydrolysis (DH). For the pretreated protein, the optimum RSM operating conditions were: hydrolysis time of 88.14 min, substrate concentration of 1.17% and enzyme to substrate (E/S) ratio of 2.18%. Under this condition, ACE inhibitory activity of the hydrolysate was 68.96%, being closely associated with the predicted value (69.68%) from the model generated based on RSM optimization.