•Frequency effects of ultrasound pretreatment on enzymolysis of RP were studied.•Structural characteristics of RP pretreated by ultrasound were further investigated.•A new tri-frequency generating ultrasound was used.The effects of ultrasound pretreatment with different frequencies and working modes, including mono-frequency ultrasound (MFU), dual-frequency ultrasound (DFU) and tri-frequency ultrasound (TFU), on the degree of hydrolysis (DH) of rice protein (RP) and angiotensin-I-converting enzyme (ACE) inhibitory activity of RP hydrolysate were investigated. Ultraviolet–visible (UV) spectroscopy, fourier transform infrared (FTIR) spectroscopy, surface hydrophobicity and scanning electron microscopy (SEM) of RP pretreated with ultrasound were measured. The results showed that ultrasound pretreatment did not increase DH of RP significantly (p > 0.05). However, all the ultrasound pretreatment increased the ACE inhibitory activity of RP hydrolysate significantly (p < 0.05). The MFU of 20 kHz showed higher ACE inhibitory activity compared to that of other MFU. The ACE inhibitory activity of sequential DFU was higher than that of simultaneous with the same frequency combination. Sequential TFU of 20/35/50 kHz produced the highest increase in ACE inhibitory activity in contrast with other ultrasound frequencies and working modes. All the results under ultrasound pretreatment showed that ultrasound frequencies and working modes were of great effect on the ACE inhibitory activity of RP. The changes in UV–Vis spectra and surface hydrophobicity indicated the unfolding of protein and exposure of hydrophobic groups by ultrasound. The FTIR analysis showed that all the ultrasound pretreatment with different frequencies and working modes decreased α-helix, β-turn content and increased β-sheet, random coil content of RP. The SEM results indicated that ultrasound pretreatment resulted in the deformation of RP. In conclusion, the frequency selection of ultrasound pretreatment of RP is essential for the preparation of ACE inhibitory peptide.

•Effects of frequency mode on ultrasound-assisted enzymolysis were studied.•Ultrasound condition was further optimized under the optimal frequency mode.•Effects of ultrasound pretreatment on the structural characteristics were studied.The effects of ultrasonic frequency mode, power density, pretreatment time and other parameters under low power density on the degree of hydrolysis (DH) of defatted wheat germ protein (DWGP) and angiotensin-I-converting enzyme (ACE) inhibitory activity of DWGP hydrolysate were studied in this research. Ultraviolet–visible (UV–Vis) spectra, free sulfhydryl (SH), disulfide bond (SS), surface hydrophobicity and hydrophobic protein content of ultrasound-pretreated protein and hydrophobic amino acid (HAA) content of alcalase-hydrolysate of DWGP were measured under optimized ultrasonic condition. The ultrasonic frequency mode with dual-fixed frequency combination of 28/40 kHz showed higher ACE inhibitory activity of DWGP hydrolysate compared with that of other ultrasound frequency modes and all the ultrasonic frequency combinations involving in 28 kHz showed higher ACE inhibitory activity. Under the dual-fixed frequency ultrasound mode of 28/40 kHz, ultrasonic power density of 60 W/L, pretreatment time of 70 min, temperature of 60°C and substrate concentration of 60 g/L, the ACE inhibitory activity of DWGP hydrolysate was the highest with its value of 74.75% (increased by 62.30% compared to control). However, all the ultrasonic pretreatment did not increase the DH of DWGP significantly (p > 0.05). The changes in UV–Vis spectra, SH and SS groups, surface hydrophobicity and hydrophobic protein content indicated that the structure of DWGP unfolded after ultrasound pretreatment. The HAA content of hydrolysate from the pretreated DWGP increased significantly (p < 0.05). The results proved that ultrasound pretreatment loosed the protein structure and exposed more HAA residues of protein to be attacked easily by alcalase. This resulted in the increase in the HAA content which related to the ACE inhibitory activity.

•HMF is prepared from glucose in water, DMSO and [Bmim]Cl with metal chlorides.•Optimal temperature/time varies with solvent/catalyst system used.•DMSO/CrCl3·6H2O results in the highest HMF yield and water/FeCl3·6H2O in the lowest yield.•Mechanism of glucose dehydration in solvent/catalyst system is proposed.•Kinetics of HMF synthesis are described.Synthesis of 5-hydroxymethylfurfural (HMF) from glucose was done in H2O, dimethylsulfoxide (DMSO) and 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) catalyzed by metal (III) chloride (FeCl3·6H2O, CrCl3·6H2O and AlCl3). The effects of solvent/catalyst system and temperature/time on the performance of the reaction are studied. HMF yield in the different solvents follows a decreasing order as DMSO > [Bmim]Cl > H2O. The highest HMF yield is achieved by CrCl3·6H2O, followed by AlCl3 and then FeCl3·6H2O. An optimal temperature/time is found at 393 K or 403 K and a time between 30 min and 480 min. Under the optimal reaction conditions, HMF yields of 54.43% and 52.86% are obtained in DMSO with CrCl3·6H2O at 403 K and 480 min and AlCl3 at 393 K and 240 min, respectively. The mechanism of the halide chlorides catalyzed glucose conversion reaction is proposed. The kinetic model is established to describe the HMF formation and the experimental data conform to the model.Conversion of glucose into 5-hydroxymethylfurfural (HMF) in H2O, DMSO and ([Bmim]Cl with metal (III) chloride catalyst.Download high-res image (96KB)Download full-size image

•Pulsed light could rapidly and completely inactivate horseradish peroxidase.•Pulsed light led to protein aggregation and denaturation.•Pulsed light could unfold the tertiary structure of protein molecules.•Pulsed light caused the secondary structure change of horseradish peroxidase.The objective of this research was to investigate the effects of pulsed light on the activity and structure of horseradish peroxidase in buffer solution. Enzyme residual activities were measured. Surface topography, secondary, and tertiary structures of horseradish peroxidase were determined using atomic force microscopy (AFM), Raman spectroscopy, and fluorescence spectroscopy, respectively. Results showed that a complete inactivation of horseradish peroxidase was achieved by application of 10 pulses of pulsed light treatment at an intensity of 500 J/pulse. The AFM analysis revealed that the aggregation of enzyme protein increased and surface roughness decreased with the increase in the treatment time. Fluorescence and Raman spectroscopy analysis exhibited that pulsed light destroyed the tertiary and secondary protein structures. The β-sheet composition was decreased while β-turn and random coils were increased. Pulsed light could effectively inactivate horseradish peroxidase by destroying the secondary and tertiary structures of protein in the active center of the enzyme.

The effects of ultrasound pretreatments on mass transfer kinetics, microstructure, carotenoid and vitamin C contents of sweet potato were investigated. Sweet potato samples were treated in distilled water with ultrasound (DWU), osmotic dehydration without ultrasound (OD) and ultrasound-assisted osmotic dehydration (UOD). Samples were subjected to ultrasound probe of 2 cm diameter, frequency of 28 kHz at 300 W maximum power at different pretreatment times of 20, 30, 45 and 60 min. The Azuara model used in this study fitted the experimental data well with high coefficient of correlation ranging from 0.92 to 0.98, low values of chi-square (<0.6), root mean square error (<0.9) and percent mean relative deviation (<10%). The results showed that UOD significantly (p < 0.05) had the highest mass transfer coefficient and equilibrium value for water loss and solid gain, compared to DWU and OD. DWU had no significant effect on the structure of sweet potato samples, while UOD had the highest effect on the structure. The samples treated in OD had the highest carotenoid retention compared to DWU and UOD at all pretreatment times. However, ultrasound enhanced the retention of vitamin C (>70%) in sweet potato samples treated in DWU and UOD.

•Heat/ultrasound pretreatment on enzymolysis of corn gluten meal protein was investigated.•Best hydrolysis rate and degree was in sonicated/preheated corn gluten meal protein.•Structure and morphology of heat/ultrasound pretreated corn protein was changed.The purpose of this study was to investigate the effect of pretreatments of heat (HP), ultrasound (UP), and combinations of heat/ultrasound (HPUP) and ultrasound/heat (UPHP) on protamex-catalyzed enzymolysis of corn gluten meal (CGM). Enzymolysis kinetics, molecular conformation and microstructure of CGM protein were monitored. Enzymolysis reaction rate increased with increasing substrate concentration and 80 g/L resulted in the highest hydrolysis reaction rate. The best improvement in CGM enzymolysis was obtained by HPUP (KM value decreased by 11.56%) and then followed by UPHP (KM value decreased by 9.97%). Fluorescence spectra and fourier transform infrared (FTIR) spectra indicated that the CGM pretreatments induced molecular unfolding, exposing the hydrophobic groups. HPUP and UPHP pretreatments both decreased the α-helix content by 12.2% and increased the random coil content by 2.23 and 2.60%, respectively. Scanning electron microscopy and atomic force microscopy showed that HPUP and UPHP changed surface topography and distribution of protein particles, enhancing the rate of enzymolysis. In conclusion, combined ultrasound and heat pretreatment and controlled enzymolysis could be an effective method for the functionality modification of globular proteins.

•An in-situ spectra monitoring system of enzymatic process was created•The optimal intervals for the enzymatic hydrolysis index of wheat gluten were selected.•Spectral quantitative models for the index of enzymatic hydrolysis of wheat gluten were established.The degree of hydrolysis (DH), peptide content and angiotensin I-converting enzyme (ACE) inhibitory activity of hydrolysates are the three most important indexes for process control in proteins enzymatic hydrolysis and ACE inhibitory peptides preparation. In this study, a miniature fiber optical spectrometer in conjunction with multivariate analysis for in-situ and real-time monitoring of the parameters (DH, peptide content and ACE inhibitory activity) in wheat gluten (WG) hydrolysis process. Synergy interval partial least square (Si-PLS) algorithm was performed to variables selection and the regression model was calibrated. The performance of a model was evaluated by the correlation coefficient (Rp) and the root mean square error (RMSEP) in the prediction set. The results showed that Rp = 0.9270, RMSEP = 1.73% for DH; Rp = 0.9673, RMSEP = 0.79 mg/ml for peptide content; Rp = 0.9507, RMSEP = 5.12% for ACE inhibitory. This work demonstrated that miniature fiber optical spectrometer combined Si-PLS model can be used as an alternative method for in-situ and real-time monitoring the enzymatic process of WG.Download high-res image (108KB)Download full-size image

•Effect of ultrasound pretreatment on fried sweet potato was investigated•Ultrasound pretreatment significantly lowered oil uptake compared to control•Ultrasound enhanced moisture transfer rate during frying•The lowest activation energy was obtained in ultrasound pretreated samplesThe possibility of ultrasound assisted pretreatments of sweet potato to lower the moisture content and oil uptake during deep fat frying and its effects on the mass transfer rate was investigated. Sweet potato samples prior to frying were immersed in distilled water with ultrasound (UD), osmotic dehydration without ultrasound (OD) and ultrasound assisted osmotic dehydration (UOD). Ultrasound probe having frequency of 28 kHz at 300 W maximum power and time of 30 min was used for the pretreatment. The control (without pretreatment) and the pretreated samples were fried using sunflower oil at temperature of 130, 150 and 170 °C for 2, 4, 6, 8 and 10 min. The first order kinetic model was used for the mass transfer rate for moisture loss and oil uptake. The lowest moisture content was found in fried samples pretreated in UOD and OD while the lowest oil uptake was obtained in fried samples pretreated in UD having 65.11 and 71.47% oil reduction at temperature of 150 and 170 °C, respectively, compared to the untreated sample. The k values of all pretreated samples were higher than that of the untreated at 150 and 170 °C. The highest activation energy for moisture loss was found in untreated samples while the lowest activation energy for oil uptake was found in samples pretreated in UOD. The results from this work proved that ultrasound is a good pretreatment that can be used to obtain a low moisture content and oil uptake during deep fat frying of sweet potato.Industrial relevanceUltrasound is a novel technology that is widely used in the food industries because of its numerous advantages over conventional methods. Its application in the frying of foods could also help in the reduction of oil uptake, thus making safe the consumption of fried foods. The information about frying kinetics could also help in the design and optimization of the process in the food industry.

•A novel method to pretreat rice protein with ultrasound assisted alkali.•Microstructures of rice protein pretreated by ultrasound assisted alkali analyzed.•Energy-gathered ultrasound equipment used.The objectives of this study were to investigate the effects of multi-frequency energy-gathered ultrasound (MFEGU) and MFEGU assisted alkaline pretreatments on the enzymolysis and the mechanism of two pretreatments accelerating the rice protein (RP) proteolysis process. The results showed that MFEGU and MFEGU assisted alkaline pretreatments improved significantly (P < 0.05) the degree of hydrolysis (DH) and the protein elution amount of RP. Furthermore under the same DH conditions, ultrasound and ultrasound assisted alkaline pretreatments were more save the enzymolysis time than the unpretreatment. The changes in UV–vis spectra, fluorescence emission spectra indicated unfolding and destruction of RP by MFEGU and MFEGU assisted alkaline pretreatments. The circular dichroism analysis showed that both pretreatments decreased α-helix but increased β-sheet and random coil of RP. Amino acid composition revealed that MFEGU and MFEGU assisted alkaline pretreatments could increase the protein elution amount and the ratio of hydrophobic amino acids. Atomic force microscopy (AFM) indicated that both pretreatments destroyed the microstructures and reduced the particle size of RP. Therefore, MFEGU and MFEGU assisted alkaline pretreatments are beneficial to improving the degree of hydrolysis due to its sonochemistry effect on the molecular conformation as well as on the microstructure of protein.

•A simplified enzymolysis kinetic equation was deduced with the impeded coefficient.•Rice protein was hydrolyzed after ultrasound and ultrasound allied alkali pretreatments.•The structure characteristics of rice protein pretreated by ultrasound and ultrasound allied alkali were studied.This research investigated the structural characteristics and enzymolysis kinetics of rice protein which was pretreated by energy-gathered ultrasound and ultrasound assisted alkali. The structural characteristics of rice protein before and after the pretreatment were performed with surface hydrophobicity and Fourier transform infrared (FTIR). There was an increase in the intensity of fluorescence spectrum and changes in functional groups after the pretreatment on rice protein compared with the control (without ultrasound and ultrasound assisted alkali processed), thus significantly enhancing efficiency of the enzymatic hydrolysis. A simplified kinetic equation for the enzymolysis model with the impeded reaction of enzyme was deduced to successfully describe the enzymatic hydrolysis of rice protein by different pretreatments. The initial observed rate constants (Kin,0) as well as ineffective coefficients (kimp) were proposed and obtained based on the experimental observation. The results showed that the parameter of kin,0 increased after ultrasound and ultrasound assisted alkali pretreatments, which proved the effects of the pretreatments on the substrate enhancing the enzymolysis process and had relation to the structure changes of the pretreatments on the substrate. Furthermore, the applicability of the simplified model was demonstrated by the enzymatic hydrolysis process for other materials.

•Immobilized enzyme was used to investigate the mechanisms of ultrasonic assisted enzymolysis.•DH significantly increased after DFU assisted-enzymolysis.•Yield of soluble solids content increased after DFU assisted-enzymolysis.•Content of α-helix and random coil in rapeseed protein decreased, β-chain increased after DFU assisted-enzymolysis.•Surface roughness of immobilized Alcalase increased after DFU assisted-enzymolysis.The mechanism of ultrasound field promoting enzymolysis efficiency is difficult to study, because the reaction system mixes with enzymes, proteins and hydrolysates. Immobilized enzyme is a good option that can be used to investigate the mechanism by separating enzymes out from the system after enzymolysis. The objective of this study was by using immobilized Alcalase to investigate the effects and mechanisms of the promotion of dual-frequency ultrasound (DFU) assisted-enzymolysis on rapeseed protein. Based on single factor experiments, response surface methodology model with three factors – hydrolysis time, power density and solid–liquid ratio at three levels was utilized to optimize the degree of hydrolysis (DH). Circular dichroism (CD) was used to analyze the secondary structure change of the protein, scanning electron microscopy (SEM) was used to analyze the surface microstructure change of the enzyme. The results showed that with DFU assisted-enzymolysis, the DH increased by 74.38% at the optimal levels for power density 57 W/L, solid–liquid ratio 5.3 g/L and enzymolysis time 76 min. After DFU assisted-enzymolysis, the yield of soluble solids content, including protein, peptides and total sugar in hydrolysate increased by 64.61%, 40.88% and 23.60%, respectively. CD analysis showed that after DFU assisted-enzymolysis, the number of α-helix and random coil decreased by 10.7% and 4.5%, β-chain increased by 2.4%. SEM showed that the degree of surface roughness of immobilized Alcalase increased. The above results indicated that the improvement of hydrolysis by DFU assisted-enzymolysis was achieved by enhancing the solid solubility, changing the molecular structure of protein and increased the surface area of immobilized enzyme.

The main objective of this research was to study the effects of ultrafine grinding and pulsed magnetic field (PMF) treatment on free gossypol (FG) content in cottonseed meal (CSM). The results revealed that FG content decreased from 831 to 584 mg kg−1 after CSM was ultrafine ground with an airflow crusher. A further decrease of FG content was achieved by processing with PMF. Response surface methodology (RSM) was applied to optimize the process of detoxification, and results showed that the influence of PMF intensity and pulse numbers was remarkable. Removal efficiency increased distinctly with increasing of PMF intensity (50–500 mT) and pulse numbers (10–60) but decreased slightly with increasing of sample weight (0.5–10 g). The relationship between the removal ratio of FG and PMF intensity, pulse numbers, and sample weight all can be expressed with quadratic equations, respectively. The total removal ratio of FG even reached 83.39 % after cottonseed coarse powder (CSCP) was processed with ultrafine grinding and PMF under conditions of PMF intensity (500 mT), pulse number (50), and sample weight (3 g). And the Box–Behnken design (BBD) generated satisfactory mathematical models that accurately explained the behavior of the system, allowing one to predict the removal efficiency of FG from CSM.

Pulsed magnetic field (PMF) technology has emerged as a non-thermal method for inhibition of spoilage microorganism in food. In this study, we evaluate the effect of PMF treatment on the inactivation of Bacillus subtilis. The mechanisms responsible for cell death were also studied using transmission electron microscopy (TEM) and proteome approaches. Results showed that the survival rate of B. subtilis generally decreased with an increase of pulse numbers at the intensity of 3.30 T. The observation of TEM showed damage in cell cytoplasm and cytoplasmic membrane after PMF treatment. Additionally, 18 differentially expressed protein spots were identified by two dimensional gel electrophoresis (2D-GE) and matrix-assisted laser desorption/ionization-time-of-flight/time-of-flight (MALDI-TOF/TOF) analysis. The down-regulated outer membrane protein A (OmpA) illustrated that PMF destroyed the cell membrane. Furthermore, Gene ontology (GO) analysis and kyoto encyclopedia of genes and genomes (KEGG) pathway analysis were used to characterize the functions of those proteins. That PMF treatment damaged the membrane component, depressed cellular molecular functions and biological process, and decreased the carbohydrate metabolism and energy metabolism, which explain the death of cells. The presented results give the better view into the proteome of food microorganism and provide insight into the nature of PMF inactivation mechanisms.

Biological effect and inactivation mechanism of Bacillus subtilis exposed to pulsed magnetic field (PMF) were investigated. Cell morphology, membrane permeability, release of intracellular proteins and damage of deoxyribonucleic acid (DNA) were monitored. The inactivation effect of PMF treatment on B. subtilis was enhanced with the increase in intensity and pulse number. Scanning electron microscopy (SEM) analysis showed that the PMF treated bacterial cells had rough surfaces and damaged cellular membranes. Flow cytometry measurements showed that the cell membrane permeability increased after the PMF treatment. Leakage of intracellular contents, measured as OD, significantly increased with the increase in PMF intensity and pulsed number. A maximum leakage of cytoplasmic contents was detected at intensity of 3.30 T and 30 pulses. Enterobacterial repetitive intergenic consensus - polymerase chain reaction (ERIC-PCR) fingerprint signaled that the DNA was fragmented after the PMF treatment at the intensity of 3.0 T with 30 pulses and 3.3 T with 10, 20 and 30 pulses. These findings may give clues to the mechanism of bacterial cell death due to the PMF treatment.

•MPU accelerated the CGM enzymolysis under different reaction conditions.•MPU increased the affinity between enzyme and CGM, accelerated the breakdown of CGM.•MPU increased reaction rate constant k significantly (P < 0.05).•MPU decreased the values of Ea, ΔH and ΔS (P < 0.05).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.

•Multi-frequency power ultrasound were employed in the enzymolysis of CGM.•Ultrasound pretreatments increased the DH and CR of CGM significantly.•The molecular conformations of zein and glutelin were investigated respectively.•SEM was adopted to study the microstructures of zein, glutelin, CGM and residues.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.

•Soybean oil deodorizer distillate was used as feedstock for biodiesel production.•A new enhancing method of counter-current probe ultrasonic was employed.•CCPUE was a better method for enhancing transesterification.•The average biodiesel conversion was 96.1% for CCPUE method.Biodiesel production from soybean oil deodorizer distillate enhanced by counter-current pulsed ultrasound was studied. Effect of static probe ultrasonic enhanced transesterification (SPUE) and counter-current probe ultrasonic enhanced transesterification (CCPUE) on the biodiesel conversion were compared. The results indicated that CCPUE was a better method for enhancing transesterification. The working conditions of CCPUE were studied by single-factor experiment design and the results showed that the optimal conditions were: initial temperature 25 °C, methanol to triglyceride molar ratio 10:1, flow rate 200 mL/min, catalyst content 1.8%, ultrasound working on-time 4 s, off-time 2 s, total working time 50 min. Under these conditions, the average biodiesel conversion of three experiments was 96.1%.

•Effects of SFCU and SFU pretreatments on ACE inhibitory activity were investigated.•Two mathematical models were developed to show the effect of each variable.•The SFCU and SFU pretreatments were compared under optimum conditions.The sweep frequency ultrasound (SFU) and single frequency countercurrent ultrasound (SFCU) pretreatments were modeled and compared based on production of angiotensin I-converting enzyme (ACE) inhibitory peptides from garlic hydrolysates. Two mathematical models were developed to show the effect of each variable and their combinatorial interactions on ACE inhibitory activity. The optimum levels of the parameters in SFU were determined using uniform design, which revealed these as follows: total ultrasonic time 1.5 h, on-time of pulse 18 s and off-time of pulse 3 s. Under optimized conditions, the experimental values of SFU and SFCU were 65.88% and 67.78%, which agreed closely with the predicted values of 63.44% and 67.33%. The SFU and SFCU pretreatments both resulted in higher ACE inhibitory activity compared with untreated garlic (p < 0.05). However, there were no significant differences in the ACE inhibitory activities and IC50 values obtained from SFCU and SFU pretreatments under optimum conditions (p > 0.05).

•The ultrasound caused viscosity to decrease exponentially with treated time.•The dynamics and theoretical derivation were established and confirmed.•The distribution and new fraction of degraded polysaccharides was found.•The cleavage preferentially took place roughly at the centre of large PP molecules.•The inhibition activities of SGC7901 with polysaccharides were increased.The exposure of polysaccharides solutions to high-energy ultrasound produces a permanent reduction in viscosity and change in activity. However, the exact mechanism which occurs in the process is still not clear. In this work, degradation of polysaccharides from Porphyra yezoensis (PP) was indirectly and directly judged by intrinsic viscosity and high performance gel permeation chromatography. The degradation process was established with dynamics and affirmed by theoretical derivation. Inhibition of cancer cell lines (SGC-7901, 95D) was also investigated by assays of tetrazolium colorimetric. The intrinsic viscosity of the degraded PP decreased exponentially with increase in ultrasonic time, and theoretical derivation was established and confirmed well. The distribution and new fraction of degraded polysaccharides was found. Ultrasound degraded preferentially large PP molecules and cleavage took place roughly at the centre of the molecules. During ultrasound degradation the molecular weight distribution was narrowed. The inhibition activities of SGC7901 with ultrasound degraded polysaccharides were increased.

•Antioxidant peptides from CGM protamex hydrolysis were prepared and optimized.•Comprehensive balance method of orthogonal design to optimize variables used.•CGM oligopeptides fraction is mainly responsible for the antioxidant activity.•CGM peptides are efficient in scavenging DPPH radical and reducing power.•Amino acids and Alanyl-Tyrosine have a role in peptide antioxidant activity.Protamex catalyzed corn gluten meal (CGM) hydrolysis peptides (CHP) were prepared. Orthogonal design L16 (45) was used to optimize processing variables of CGM concentration, CGM heat pretreatment (121 °C) time, and enzymolysis pH, temperature, and time. Degree of hydrolysis (DH), undigested residue ratio, molecular weight (MW) distribution and DPPH radical inhibition were selected as analysis indicators. Optimum variables were CGM concentration of 18%, heat pretreatment time of 40 min, and enzymolysis pH, temperature and time of 7.5, 55 °C and 24 h, respectively. Verification test showed that CHP IC50 for scavenging hydroxyl radical was the best and then followed by reducing power. Oligopeptides improved after hydrolysis at the expense of di- and tripeptides, suggesting formation of soluble aggregates from low MW peptides. The increase in the DH, oligopeptides, Alanyl-Tyrosine, and antioxidant free amino acids coincided with the improvement in the antioxidant activity of CHP.

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.

Acetobacter pasteurianus plays an important role in the process of traditional vinegar production and is also essential for the fermentation of Zhenjiang aromatic vinegar. In this study, we utilized the proteomic approach to analyze the proteomic profile of A. pasteurianus HSZ3-21, and 258 proteins were successfully identified by MALDI–TOF-MS and database search. The hydropathy and GO analyse combined with COG results of the identified proteins revealed the molecular biological characteristics of A. pasteurianus proteins, that is, most proteins of A. pasteurianus were related to metabolic process, binding, catalytic or cellular response. Meanwhile, our results also showed that some proteins of A. pasteurianus may be responsible for acetic acid tolerance, thermotolerance, and stress response. Therefore, the identification of 258 proteins not only deciphers protein composition and functional classification of A. pasteurianus, but also provides useful information for improving quality of Zhenjiang aromatic vinegar.

•Seven Cnmim/FeCl4 magnetic and acidic ionic liquids (MAILs) were synthesized.•The MAILs were characterized with Raman, FT-IR, TGA, UV spectra and MPMS.•MAILs contained FeCl4−/Cnmim+ exhibit typical hard magnetic materials behavior.•Introducing Cnmim/MCl3 as catalysts for hydrolysis of sugars to platform chemicals.•C3mim/WCl3 is found to be very effective for conversion glucose/xylose to HMF.The exploitation of dual functional magnetic and acidic ionic liquids (MAILs) for hydrolysis of cellulose to platform chemicals can solve some practical challenges through easy separation of products and efficient catalyst recyclability. In this work, seven Cnmim/FeCl4 MAILs were synthesized and investigated with combined experimental and molecular dynamics. The MAILs contained FeCl4− anions and exhibited a typical hard magnetic materials behavior with rather strong magnetic susceptibilities. These MAILs were stable up to 250–310 °C, the decomposition was started up at 250/310–480–810 °C in two steps with the formation of the undecomposed residue. The Gibbs energy for the reaction of glucose/xylose conversion to 5-hydroxymethylfurfural by metal chlorides in the CnmimCl ionic liquid was studied using the density functional theory calculations and the results that C3mim/WCl3 may be the most hopeful catalyst. The MAILs have the potential to open up promising new catalytic systems because of their easy product separation and efficient catalyst recyclability.

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.

•Athermal effects of microwave on simplified model as glucose/glycine were examined.•Microwave and bath heating did not cause any change of Maillard reaction products.•All data failed to show any significant athermal effects in compositional changes.Many reports claim the existence of athermal effects in microwave-induced reactions, and this challenge the assumption that the thermal effect (heating) is the sole factor in microwave heating. Therefore, microwave-induced Maillard reaction of d-glucose/glycine and degradation of polysaccharide from Porphyra yezoensis (PSPY) were investigated. Browning reactions were monitored by measuring heating rate, UV-absorbance and brown color, UV–vis and synchronous fluorescence spectra, GC/MS analysis and intrinsic viscosity of degradation. Heating of d-glucose/glycine solution produced brown compounds which were detected at A420, and the intermediate products, 2-acetylfuran and 5-methylfurfural, whose fluorescence intensity evidenced their formation. Maximum emission of synchronous fluorescence spectra of samples were at 430–440 nm and 370–390 nm. Both microwave and water bath heating did not cause any compositional changes in the Maillard reaction products. All data failed to show any significant athermal effects of compositional changes in the Maillard reaction products. It can be inferred that some of the reports suggesting the existence of athermal effects, which could ascribe to the different set-up obtained in not well temperature controlled microwave heating systems.

Short peptides from different sources have been proven to be very efficient inhibitors of angiotensin I-converting enzyme (ACE), an enzyme with a major role in the regulation of blood pressure. In order to obtain ACE-inhibitory peptides from Tenebrio molitor (L.) larva, enzymatic hydrolysis was performed using Alcalase. The hydrolysate (DH 20 %) with the highest ACE inhibition was fractionated into four peaks according to their relative molecular weight by gel filtration on Sephadex G-15. The IC50 value of peak 2 (with the relative molecular weight 180–500 Da) was 0.23 mg/mL, while it was 0.39 mg/mL of hydrolysate before fractionation determined by reversed-phase high performance liquid chromatography (RP-HPLC). Antihypertensive activity of peak 2 was proven by single oral administration to spontaneously hypertensive rats (SHR). Multiple dose oral administration (100, 200, and 400 mg/kg body weight) to SHR led to a significant decrease in blood pressure for peak 2. The reduction of systolic blood pressure even reached 27 mm Hg at 4 h post-administration at a dose of 400 mg/kg body weight. Additionally, further separation and purification of the ACE-inhibitory peptides from peak 2 were performed using RP-HPLC on C18 column. Then a novel peptide Tyr–Ala–Asn was identified by tandem mass spectrometry with an IC50 value of 0.017 mg/mL. The result of research indicates that Tenebrio molitor (L.) larva protein may be a suitable candidate to prepare ACE-inhibitory peptides which could be used for food industry and nutraceuticals.

The degree of hydrolysis (DH) and angiotensin I-converting enzyme (ACE)-inhibitory activity of vital wheat gluten (VWG) hydrolyzed using Alcalase were investigated using Box-Behnken response surface methodology (RSM). The mean responses were fitted to a second order polynomial to obtain regression equations. The enzyme-substrate ratio and the hydrolysis time increased the DH significantly (p<0.05). The substrate concentration was the only significant linear term leading to an increase in ACE-inhibitory activity. The optimized conditions of a substrate concentration of 5.04%, an enzyme-substrate ratio 5.94%, and a hydrolysis time 30.79 min gave a point prediction of a 12.74% DH and 82.28% ACE-inhibitory activity. Analytical results from confirmatory experiment were a 12.22%±0.5 DH and a 78.93%±1.07 ACE-inhibitory activity. The optimized conditions of the study provide useful information to the functional food and beverage industries to enhance the anti-hypertensive activities of peptides from VWG.

There is a great demand for developing efficient enzymolysis methods in order to increase the enzymolysis efficiencies and activities of angiotensin converting enzyme (ACE) inhibitory peptides from wheat germ protein. The enzymolysis kinetics, ACE inhibitory activity of peptide and conversion rate of protein were studied using sweep frequency and pulsed (SFP) ultrasound-assisted enzymolysis and the results were compared with traditional enzymolysis. The studied factors were enzymolysis time and substrate concentration. By considering the activity of ACE inhibitory peptide and operation cost, the recommended conditions of SFP ultrasound-assisted enzymolysis were enzymolysis time of 120 min and substrate concentration of 24.0 g/L, which gave high conversion rates of protein (60.7%) and ACE inhibitory activity of peptide (65.9%). Compared to traditional enzymolysis, SFP ultrasound-assisted enzymolysis significantly increased the initial reaction rate (V) by 60.0% at substrate concentration of 24.0 g/L, increased the apparent breakdown rate constant (kA) by 66.7%, decreased the apparent constant (KM) by 6.9%, and raised the conversion rate of protein by 35.5% and ACE inhibitory activity of peptides by 35.6% under the recommended conditions. It has been concluded that SFP ultrasound can remarkably raise the enzymolysis efficiency and activity of ACE inhibitory peptides from wheat germ protein.

The chemical structure and antioxidant of natural and ultrasonic degraded polysaccharides from Porphyra yezoensis Udea was investigated. The degraded polysaccharide (PYPSUD) was purified, and F2 (a homogeneous fraction) was obtained. FT-IR, 1H and 13C NMR spectral analysis revealed that F2 have typical porphyran structure. It has a backbone of alternating (1 → 4)-3,6-anhydro-α-l-galactopyranose) units and (1 → 3)-linked β-d-galactose or (1 → 4)-linked α-l-galactose 6-sulfate units. The result ascertained ultrasound degradation did not change the main structure of polysaccharides in the test conditions. Antioxidant proved that the activity of scavenging superoxide and hydroxyl radical is F2 > VC > PSPYUD > PSPY. It was possible that ultrasonic treatment is an effective way for enhancing PSPY's antioxidant activity ascribing to decreasing molecular weight of polysaccharides.

The effects of ultrasonic treatment during proteolysis on kinetic characterisation of the hydrolysis of defatted wheat germ protein (DWGP), and on ACE-inhibitory activity of the hydrolysate, were investigated. The effects of ultrasonic pretreatment on the release of peptides with ACE-inhibitory were also studied. The results showed that the value of kA for DWGP hydrolysis under ultrasonic irradiation increased by about 22.2%, and KM decreased about 13.0%, compared with that obtained without ultrasound. Analysis of ACE-inhibitory activity indicated that ultrasound during enzyme treatments had less effect on the ACE-inhibitory activity, while ultrasonic pretreatment caused a 21.0–40.7% increase in ACE-inhibitory activity of DWGP hydrolysate. Analyses of hydrophobicity, microstructure, and amino acid composition revealed that ultrasonic pretreatment could accelerate the release of hydrophobic amino acids from DWGP during enzymatic hydrolysis. In conclusion, ultrasonic treatment during proteolysis could facilitate the enzymatic hydrolysis of DWGP, whereas ultrasonic pretreatment could promote the release of ACE-inhibitory peptides from DWGP during enzymatic hydrolysis.

This research was to develop a antihypertensive peptide, an efficient angiotensin converting enzyme (ACE) inhibitor (ACEI), from Porphyra yezoensis. Seven commercial enzymes were screened and then enzymatic hydrolysis conditions were optimised. The results showed that alcalase was the most effective for hydrolysis and its optimum conditions for achieving the highest antihypertensive activity of peptide were 1.5% substrate, 5% alcalase, pH 9.0, and temperature of 50 °C at a hydrolysis time of 60 min. The antihypertensive peptide produced under the optimum conditions had a high ACE inhibition rate of 55.0% and a low IC50 value of 1.6 g/l and remained at high stability at temperatures of 4, 25, and 37 °C, pH values of 2.0 and 8.0, and after pepsin and trypsin treatments. Major proteins from P. yezoensis were glutelin, albumin, and gliadin. The albumin and glutelin had higher hydrolysis rates than the gliadin, but the IC50 value of glutelin was the lowest, which indicated that the antihypertensive peptide from glutelin was more functional.

•Ultrasound pretreatment of substrate/enzyme before prepare ACE inhibition peptides.•Neutrase activity increased by 8.74% after sonication at 250 W for 15 min.•ACE inhibition of pretreated at 250 W for 10 min CGM protein increased by 18.27%.•Protein unfolding of CGM and neutrase after sonication was found.The impact of ultrasound pretreatment of corn gluten meal (CGM) protein and neutrase on the ACE (angiotensin converting enzyme) inhibitory activity of hydrolysate was studied. The UV–vis differential spectra and fluorescence spectra of the CGM protein and neutrase were determined. The neutrase activity and the ACE inhibitory activity of the CGM protein hydrolysates were analyzed. The highest ACE inhibitory activity was obtained at 10 min hydrolysis when the CGM protein was pretreated at 20 kHz for 10–30 min and at a power of 1000 W. The neutrase activity and ACE inhibitory activity were at their maxima at sonication of 250 W and sonication time of 15 min. The fluorescence and UV differential spectra of the proteins of CGM and neutrase reflected molecular unfolding due to sonication. Sonication of the protein substrate and the enzyme before hydrolysis may be an effective way to enhance the ACE inhibition attributes of the hydrolysate.

•Effect of ultrasound on kinetic constants of garlic enzymolysis was investigated.•Hydrolysis curves of garlic catalyzed by alcalase were determined.•The enzymolysis process was modeled over a wide range of operating conditions.This research was to describe the enzymolysis process of garlic powder which was pretreated by single frequency countercurrent ultrasound. The kinetic constants for ultrasonic pretreated and traditional enzymolysis have been determined. Results showed the value of KM in ultrasonic pretreated enzymolysis decreased by 12.7% over the traditional enzymolysis, which indicates a fast reaction speed induced by ultrasound pretreatment. Degrees of hydrolysis (DH) in the enzymolysis of garlic powder were determined and kinetics of the reaction was considered in detail in relation to substrate concentration, enzyme concentration, reaction time and DH. Our results suggested a general kinetic equation for the enzymolysis model of ultrasonic pretreated garlic powder. For the model system, the calculated values agree well with the experimental data with average relative error of 4.42%. The proposed kinetic equation can be used to model the bio-reaction process of protein enzymatic hydrolysis and optimize the operation parameters for bioreactor design.