Abstract:In this paper，angiotensin convert enzyme （ACE）inhibitory peptides were prepared via hydrolysis of sea cucumber gonads using an ultrasound technique （0-500 W，0-35 min）catalyzed by a neutral protease（0.5%-5%，1 h-6 h，1 500 U/g-7 500 U/g），and the digestion stability of these peptides was analyzed by simulating in vitro digestion experiments.The experimental results showed that the ACE-inhibition rate presented a trend of increasing first and then decreasing with an increase in ultrasound power，ultrasound exposure time，substrate concentration，enzymolysis time，and enzyme addition amount.With the increase in ultrasound power，ultrasound exposure time，and substrate concentration，the degree of hydrolysis（DH）exhibited the same changing trend；with the increase in enzymolysis time and enzyme addition amount，the DH gradually increased and then stabilized.According to the changes in DH and ACE-inhibition rate，the conditions of ultrasound pretreatment and enzymatic hydrolysis for the efficient preparation of ACE-inhibitory peptides from sea cucumber gonads were as follows：when the ultrasound pretreatment power was 200 W，the ultrasound pretreatment time was 15 min，substrate concentration was 2%，enzyme addition amount was 4 500 U/g，enzymolysis time was 2 h，and DH and ACE-inhibition rate of the sea cucumber gonad enzymatic hydrolysate were high，which were 7.81% and 73.81%，respectively.The ACE-inhibitory peptide prepared from sea cucumber gonads under these conditions was subjected to simulated gastrointestinal digestion experiments after ultrafiltration.There was no significant difference in the activity of the ACE-inhibitory peptide in the sea cucumber gonad before and after digestion（P＞0.05），indicating that it had good stability in vivo and stably lowered blood pressure.