Effects of ultrasound pretreatment with different frequencies on the degree of hydrolysis and ACE inhibitory activity of stevia protein

Abstract

The effects of ultrasound pretreatment with different frequencies and operational modes, including single frequency ultrasound and dual-frequency ultrasound on the degree of hydrolysis (DH) of stevia protein (SP) and angiotensin-I-converting enzyme (ACE) inhibitory activity of SP hydrolysate were investigated. The results of this study indicated that ultrasound pretreatment did not influence DH of SP significantly However, all the ultrasound pretreatment influence the ACE inhibitory activity of SP hydrolysate significantly. The maximum DH under ultrasonic treatment with ideal settings was found to be 11.6% .The dual frequncy ultrasound pretreatment of 20/28 kHz showed higher ACE inhibitory activity compared to that of other single frequency ultrasound and control. In conclusion, the perfect choice of frequency ultrasound pretreatment of SP is indispensable for the preparation of ACE inhibitory peptide.