Abstract:

In the present study, response surface methodology was used to optimize the process conditions for the hydrolysis
of amaranth protein by alcalase to prepare highly active angiotensin-I converting enzyme (ACE) inhibitory peptides. One-factorat-
a-time designs were used to analyze the effect of enzyme type, hydrolysis time, substrate concentration, enzyme/substrate
ratio, hydrolysis pH and hydrolysis temperature on the degree of hydrolysis (DH) and ACE inhibitory activity of amaranth
protein hydrolysate. A quadratic regression model describing ACE inhibitory rate as a function of three variables was fitted by
using an orthogonal rotary composite design. The optimal hydrolysis conditions were obtained from the regression model as
follows: enzyme/substrate ratio of 3.50%, hydrolysis pH of 8.78, hydrolysis temperature of 54.4 ℃, substrate concentration of
4 g/100 mL and hydrolysis time of 3 h. Under these conditions, the ACE inhibitory activity of the obtained hydrolysate was
46.45%, which was close to the predicted value. At the same time, the IC50 of the hydrolysate was 0.756 mg/mL.

Key words: amaranth, ACE inhibitory peptide, enzymatic hydrolysis, response surface methodology