title: Effects and mechanism of ultrasound pretreatment on rapeseed protein enzymolysis.
abstract: BACKGROUND
  The disadvantages which stem from the use of traditional enzymolysis of protein has necessitated the need to employ sweeping frequency and pulsed ultrasound (SFPU) in the pretreatment of rapeseed protein prior to proteolysis in order to bring about improvement in enzymolysis efficiency. Further, in order to determine the mechanism of ultrasound-accelerated enzymolysis of RP, the effects of SFPU on the kinetics, thermodynamics, molecular conformation and microstructure of RP were investigated.
  
  
  RESULTS
  Kinetic studies showed that SFPU pretreatment on RP improved enzymolysis by decreasing the apparent constant KM significantly (P < 0.05) by 32.8% and reducing the thermodynamic parameters Ea , ΔH and ΔS by 16.6%, 17.7% and 9.2% respectively. Fluorescence spectra revealed that SFPU pretreatment induced molecular unfolding, causing more hydrophobic groups and regions inside the molecules to be exposed to the outside. Circular dichroism analysis indicated that SFPU pretreatment decreased the α-helix content by 16.1% and increased the random coil content by 3.6%. In addition, scanning electron microscopy showed that SFPU pretreatment increased the specific surface area of RP.
  
  
  CONCLUSIONS
  Ultrasound pretreatment is an efficient method in RP proteolysis to produce peptides through its impact on the molecular conformation and microstructure of proteins.
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Jin
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China.|Jiangsu Provincial Key Laboratory for Physical Processing of Agricultural Products, Zhenjiang, Jiangsu, 212013, China.
authors.forename: Haile
authors.initials: H
authors.lastname: Ma
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Wang
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China.
authors.forename: Min
authors.initials: M
authors.lastname: Luo
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China.
authors.forename: Bei
authors.initials: B
authors.lastname: Wang
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China.
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Qu
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China.|Jiangsu Provincial Key Laboratory for Physical Processing of Agricultural Products, Zhenjiang, Jiangsu, 212013, China.
authors.forename: Ronghai
authors.initials: R
authors.lastname: He
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China.|Department of Hospitality, School of Applied Science and Technology, Koforidua Polytechnic, PO Box 981, Koforidua, Ghana.
authors.forename: John
authors.initials: J
authors.lastname: Owusu
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu, 212013, China.
authors.forename: Yunliang
authors.initials: Y
authors.lastname: Li
mesh_terms: D029741:Brassica rapa / Q000737:chemistry*; D006801:Humans; D010940:Plant Proteins / Q000737:chemistry*; D058767:Protein Unfolding; D013329:Structure-Activity Relationship; D000069453:Ultrasonic Waves
chemical_list: D010940:Plant Proteins
keywords: circular dichroism; kinetics; rapeseed protein; scanning electron microscopy; thermodynamics; ultrasound