European Food Research and Technology

, Volume 238, Issue 3, pp 435–442 | Cite as

Effects of sweeping frequency ultrasound treatment on enzymatic preparations of ACE-inhibitory peptides from zein

  • Xiaofeng Ren
  • Haile Ma
  • Shuyun Mao
  • Huiji Zhou
Original Paper


In this study, the effect of sweeping frequency ultrasound (SFU) treatment on the degree of hydrolysis of zein and the angiotensin I-converting enzyme (ACE)-inhibitory activity of its hydrolysates were investigated. The mechanism through which ultrasonic pretreatment releases peptides with ACE-inhibitory activity was also studied by fluorescence, circular dichroism (CD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Compared to the control, SFU and fixed frequency ultrasound (FFU) increased the degree of zein hydrolysis by approximately 11.5 %. Sweeping frequency ultrasound pretreatment increased ACE-inhibitory activity of zein hydrolysates by 12.3–116.7 % over the control. At 40 ± 2 kHz, SFU-treated zein hydrolysates had 42.9 % ACE-inhibitory activity, representing an increase of 116.7 % over the control. The fluorescence intensity of SFU- and FFU-treated zein was weaker than in untreated zein, indicating that more Phe, Trp, and Tyr residues were exposed outside the polypeptide chains. CD spectra show that SFU treatment resulted in increase in the α-helix content by 3.4 %, and β-sheet, β-turns, and random coils content by 24.4 %. Analyses of microstructure by SEM and AFM revealed that ultrasonic pretreatment ruptured the fine meshwork structure of zein resulting in the appearance of several micro-holes. We conclude that the SFU pretreatment for 40 ± 2 kHz can remarkably raise the degree of zein hydrolysis and ACE-inhibitory activity of the hydrolysates by altering the second structure of zein and rupturing the smooth surface of protein.


Zein Sweeping frequency Ultrasound Angiotensin I-converting enzyme 



The authors wish to extend our appreciation for the support provided by National 863 Plan of China (Hi-Tech Research and Development Program of China) (2013AA100203), the National Natural Science Foundation of China (NNSFC-31071502), the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions, Nature Science Foundation of Jiangsu Provincial Education Department (11KJB550001), and Research-Innovation Program of Postgraduate in General Universities of Jiangsu (CX10B_279Z), China.

Conflict of interest


Compliance with Ethics Requirements

This article does not contain any studies with human or animal subjects.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Xiaofeng Ren
    • 1
  • Haile Ma
    • 1
    • 2
  • Shuyun Mao
    • 1
  • Huiji Zhou
    • 1
  1. 1.School of Food and Biological EngineeringJiangsu UniversityZhenjiangPeople’s Republic of China
  2. 2.Jiangsu Provincial Key Laboratory for Physical Processing of Agricultural ProductsJiangsu UniversityZhenjiangPeople’s Republic of China

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