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Jin J.,Jiangsu University | Jin J.,Jiangsu Provincial Key Laboratory for Physical Processing of Agricultural Products | Ma H.,Jiangsu University | Ma H.,Jiangsu Provincial Key Laboratory for Physical Processing of Agricultural Products | And 11 more authors.
Ultrasonics Sonochemistry | Year: 2015

The effects of multi-frequency power ultrasound (MPU) pretreatment on the kinetics and thermodynamics of corn gluten meal (CGM) were investigated in this research. The apparent constant (KM), apparent break-down rate constant (kA), reaction rate constants (k), energy of activation (Ea), enthalpy of activation (ΔH), entropy of activation (ΔS) and Gibbs free energy of activation (ΔG) were determined by means of the Michaelis-Menten equation, first-order kinetics model, Arrhenius equation and transition state theory, respectively. The results showed that MPU pretreatment can accelerate the enzymolysis of CGM under different enzymolysis conditions, viz. substrate concentration, enzyme concentration, pH, and temperature. Kinetics analysis revealed that MPU pretreatment decreased the KM value by 26.1% and increased the kA value by 7.3%, indicating ultrasound pretreatment increased the affinity between enzyme and substrate. In addition, the values of k for ultrasound pretreatment were increased by 84.8%, 41.9%, 28.9%, and 18.8% at the temperature of 293, 303, 313 and 323 K, respectively. For the thermodynamic parameters, ultrasound decreased Ea, ΔH and ΔS by 23.0%, 24.3% and 25.3%, respectively, but ultrasound had little change in ΔG value in the temperature range of 293-323 K. In conclusion, MPU pretreatment could remarkably enhance the enzymolysis of CGM, and this method can be applied to protein proteolysis industry to produce peptides. © 2015 Elsevier B.V. Source

Jin J.,Jiangsu University | Ma H.,Jiangsu University | Ma H.,Jiangsu Provincial Key Laboratory for Physical Processing of Agricultural Products | Wang W.,Jiangsu University | And 8 more authors.
Journal of the Science of Food and Agriculture | Year: 2016

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. CONCLUSION: Ultrasound pretreatment is an efficient method in RP proteolysis to produce peptides through its impact on the molecular conformation and microstructure of proteins. © 2015. Society of Chemical Industry. Source

Jin J.,Jiangsu University | Ma H.,Jiangsu University | Ma H.,Jiangsu Provincial Key Laboratory for Physical Processing of Agricultural Products | Wang K.,Jiangsu University | And 12 more authors.
Ultrasonics Sonochemistry | Year: 2015

The aim of this study was to investigate the effect of multi-frequency power ultrasound (sweeping frequency and pulsed ultrasound (SFPU) and sequential dual frequency ultrasound (SDFU)) on the enzymolysis of corn gluten meal (CGM) and on the structures of the major protein fractions (zein, glutelin) of CGM. The results showed that multi-frequency power ultrasound pretreatments improved significantly (P <0.05) the degree of hydrolysis and conversion rate of CGM. The changes in UV-Vis spectra, fluorescence emission spectra, surface hydrophobicity (H0), and the content of SH and SS groups indicated unfolding of zein and glutelin by ultrasound. The circular dichroism analysis showed that both pretreatments decreased α-helix and increased β-sheet of glutelin. The SFPU pretreatment had little impact on the secondary structure of zein, while the SDFU increased the α-helix and decreased the β-sheet remarkably. Scanning electron microscope indicated that both pretreatments destroyed the microstructures of glutelin and CGM, reduced the particle size of zein despite that the SDFU induced aggregation was observed. In conclusion, multi-frequency power ultrasound pretreatment is an efficient method in protein proteolysis due to its sonochemistry effect on the molecular conformation as well as on the microstructure of protein. © 2014 Elsevier B.V. Source

Jin J.,Jiangsu University | Jin J.,Southwest University of Science and Technology | Ma H.,Jiangsu University | Ma H.,Jiangsu Provincial Key Laboratory for Physical Processing of Agricultural Products | And 8 more authors.
Ultrasonics Sonochemistry | Year: 2016

The impact of dual-frequency power ultrasound (DPU) on the molecular weight distribution (MWD) of corn gluten meal (CGM) hydrolysates and its mechanism were investigated in the present study. The mechanism was studied from aspects of structural and nano-mechanical characteristics of the major protein fractions of CGM, viz. zein and glutelin. The results of molecular weight distribution indicated that DPU pretreatment of CGM was beneficial to the preparation of peptides with molecular weights of 200-1000 Da. Moreover, FTIR spectral analysis and atomic force microscopy characterization showed that the DPU pretreatment changed the contents of secondary structure of proteins, decreased the particle height and surface roughness of glutelin, reduced the Young's modulus and stiffness of zein while increased its adhesion force. In conclusion, DPU pretreatment of proteins before proteolysis is an efficient alternative method to produce short-chain peptides because of its positive effects originating from acoustic cavitation on the molecular conformation, nano-structures and nano-mechanical properties of proteins as well. © 2015 Elsevier B.V. Source

Wang B.,Jiangsu University | Wang B.,University of California at Davis | Atungulu G.G.,University of Arkansas | Khir R.,University of California at Davis | And 6 more authors.
Food Biophysics | Year: 2015

Pretreatment of oat protein with ultrasound showed excellent prospects in increasing the efficiencies of enzymatic hydrolysis and inhibitory activities of peptides against angiotensin converting enzyme (ACE). The mechanism of the ultrasound pretreatment on enhancement of protein hydrolysis rate and the characterization of the enzymolysis process was investigated. The Michaelis-Menten model was used to study the effects of ultrasound on the hydrolysis rate. An ordered sequential bi-substrate reaction mechanism model was applied to describe the characteristics of enzymolysis of the protein with ultrasonic pretreatment. The protein concentration and the enzyme loading were factors in this model. The kinetic parameters of the models were estimated by experimental results and evaluated. The results showed that ultrasonic power, time and enzymolysis time greatly influenced the degree of hydrolysis and ACE inhibitory activities of the peptides. The best conditions for hydrolysis and ACE inhibitory activities were 750 W, 20 min of sonication followed by 60 min of enzymolysis. After the treatment, the hydrolysis rate and the ACE inhibitory activities of peptides were significantly (P < 0.001) increased by 32.1 and 53.8 %, respectively compared to the samples without ultrasonic pretreatment. The Michaelis constant Km indicated the ultrasonic treatment enhanced the affinities between the alcalase and oat protein. The enzymolysis kinetic model fitted well the enzyme catalyzed hydrolysis trend for the ultrasonic pretreated oat protein. The model provided a theoretical basis for describing the complex enzymatic process and preparing the ACE inhibitory peptides efficiently. © 2014, Springer Science+Business Media New York. Source

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