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The production of bioactive peptides from egg white proteins (EWPs) and their separation are emerging areas with many new applications. The objective of this study was to compare antioxidant activity of three distinct EWP hydrolysates and their peptide fractions prepared by membrane ultrafiltration using membranes with 30, 10 and 1 kDa molecular weight cut-off. The hydrolysates were obtained by thermal and ultrasound pretreated EWPs hydrolyzed with a bacterial protease, Alcalase. It appeared that the pretreatment significantly affected peptide profiles and antioxidant activity of the hydrolysates measured by ABTS, DPPH and FRAP methods. The hydrolysate prepared using Alcalase and ultrasound pretreatment at 40 kHz - 15 min has shown to be the most effective in scavenging both DPPH and ABTS radicals (28.10±1.38 and 79.44±2.31%, respectively). It has been noticed that this hydrolysate had a nutritionally more adequate peptide profile than the other hydrolysates with a much lower amount of peptides

In order to confirm the gluten potential for inclusion into functional foods, the synergistic effect of the heat treatment and controlled enzymatic hydrolysis on the functional and the antioxidant properties of alcalase-assisted wheat gluten hydrolysates (AWGHs) will be discussed. For this purpose, wheat gluten was heat-treated during 30 min at 75 °C and intensively hydrolyzed with alcalase at degree of hydrolysis ( DH) 16.1%, 22.9%, and 30.2%. All the hydrolysates had excellent solubility over a pH range of 2-12. Emulsifying activity and stability were also improved, while proteolysis was deleterious to foam capacity and stability, water-holding capacity, fat-binding capacity and did not show improvement at higher DH (22.9% and 30.2%). As well, controlled hydrolysis of heat-treated gluten resulted in a remarkable improvement in antioxidant activities. The results show that the heat-treated AWGHs were superior to the untreated hydrolysate in the functional and antioxidant properties tested. Practical applications This report examines existing evidence regarding the wheat gluten proteins (WGP), which is a byproduct from wheat starch processing. It is known that enzymatic hydrolysis is frequently used to improve functional properties of protein hydrolysates and largely dependent on the degree of hydrolysis ( DH), which needs to be controlled to elude redundant proteolysis that can deteriorate functionality and cause unfavorable effects. The DH is a substantial factor which affect the hydrolysates' performances and an appropriate selection of protease for WGP hydrolysis will result in maximum biological activity and improved functionalities. Heat treatment is often used to facilitate the proteolysis of proteins. Thus, functional and antioxidant properties of WGP hydrolysates, as a function of heat treatment and the DH were adequately examined in this study and results showed that by combining heat prehydrolysis treatment under controlled conditions, hydrolysates with improved properties can be produced enhancing utilization of WGP in food products. [ABSTRACT FROM AUTHOR]

The objective of this research was to investigate the impact of high-intensity ultrasound (HIU) generated by a probe-type sonicator (frequency 20 ± 0.2 kHz and an amplitude of 40%) for 2-20 min on the selected functional and structural properties of egg white proteins (EWPs) and their susceptibility to hydrolysis by alcalase. The protein solubility, foaming, and emulsifying properties were studied as a function of ultrasonication time and related to protein particle and structural properties. The length of ultrasonication exhibited important effect on EWP particle size, uniformity, and charge, affecting also the protein conformation and susceptibility to alcalase hydrolysis and determining functional properties. There was a linear correlation between the particle size decrease and the solubility while a two-step linear correlation between the foam capacity (FC)/foam stability (FS) and particle size was apparent. Specifically, FC and FS sharply increased with decreasing particle size for range from ∼370 to ∼260 nm, and below this range from 260.6 to 68.4 nm, the changes were not that substantial. Besides, the solubility, FC, and FS were directly and linearly related with the absolute value of the particle zeta potential. The overall emulsifying properties were also improved with an increase of sonication time, through both the decrease of the mean particle diameter and the increase of zeta potential, but there was no direct correlation between the emulsion activity/stability index and protein particle size and/or charge. Analysis of EWP structure by Raman spectroscopy revealed that the HIU leads to changes in the secondary structure, while heat and ultrasound generated by the ultrasound bath were not sufficient to exhibit this effect. [ABSTRACT FROM AUTHOR]

The impact of ultrasound waves generated by probe-type sonicator and ultrasound cleaning bath on egg white protein susceptibility to hydrolysis by alcalase compared to both thermal pretreatment and conventional enzymatic hydrolysis was quantitatively investigated. A series of hydrolytic reactions was carried out in a stirred tank reactor at different substrate concentrations, enzyme concentrations, and temperatures using untreated, and pretreated egg white proteins (EWPs). The kinetic model based on substrate inhibition and second-order enzyme deactivation successfully predicts the experimental behavior providing an effective tool for comparison and optimization. The ultrasound pretreatments appear to greatly improve the enzymatic hydrolysis of EWPs under different conditions when compare to other methods. The apparent reaction rate constants for proteolysis ( k2) are 0.009, 0.011, 0.053, and 0.045 min−1 for untreated EWPs, and those pretreated with heat, probe-type sonicator, and ultrasound cleaning bath technologies, respectively. The ultrasound pretreatment also decreases hydrolysis activation ( Ea) and enzyme deactivation ( Ed) energy, enthalpy (Δ H), and entropy (Δ S) of activation and for the probe-type sonication this decrease is 61.7%, 61.6%, 63.6%, and 32.2%, respectively, but ultrasound has little change in Gibbs free energy value in the temperature range of 318 to 338 K. The content of sulfhydryl groups and ζ potential show a significant increase ( P < 0.05) for both applied ultrasound pretreatments and the reduction of particle size distribution are achieved, providing some evidence that the ultrasound causes EWP structural changes affecting the proteolysis rate. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effects of different ultrasound pretreatment on enzymatic hydrolysis of egg white proteins (EWPs) by Alcalase as well as evaluating some functional and antioxidant properties of hydrolysates obtained by various proteases treatment and ultrasound technology. The effects of chosen ultrasound pretreatment parameters including frequency of ultrasonic waves (35 and 40 kHz), temperature (25 and 55 °C), time of pretreatment (15-60 min) and pH of egg white solution (7.00-10.00) were examined. It appeared that controlled ultrasound treatment can improved the hydrolysis process compared with untreated samples, but optimization of the power and length of sonication was important. The optimal ultrasound pretreatment at calorimetric power of 21.3 W and frequency of 40 kHz for 15 min at 25 °C and with naturally basic egg white (pH 9.25) resulted in increased initial rate and equilibrium degree of Alcalase hydrolysis by about 139.8 and 13.86 % compared with the control, respectively. EWP hydrolysates with ≈27.0 % degree of hydrolysis obtained with heat pretreatment and ultrasound pretreatments under optimal conditions were further separated by sequential ultrafiltration into 4 hydrolysate fractions (<1, 1-10, 10-30 and >30 kDa) which were investigated for protein content, peptide yield and antioxidant activity. The hydrolysis after heat pretreatment generated more peptides <1 kDa (19.04 ± 1.02 %) than ultrasound pretreatment did (11.90 ± 0.53 %), whereas the proportion of peptides <10 kDa were higher in the second case (28.80 ± 0.07 vs. 20.46 ± 0.39 %). The fraction obtained by the ultrasound pretreatment containing peptides with a molecular weight between 1 and 10 kDa demonstrated the strongest ABTS radical scavenging efficacy among the fractions (97.54 ± 0.30) with IC value of 4.31 mg/mL. Compared with single-enzyme processes, the two-stage enzymatic processes did not significantly improve both antioxidant and functional hydrolysates' properties. [ABSTRACT FROM AUTHOR]

The aim of the study was to find the optimal operational and process parameters for the enzymatic hydrolysis of wheat gluten in a batch stirred bioreactor regarding both degree of hydrolysis and antioxidant capacity of the obtained hydrolysates. It appeared that impeller geometry and agitation speed influenced the mass transfer resulting in enhanced gluten hydrolysis. The highest initial reaction rate (0.83 ± 0.02 min −1 ) and degree of hydrolysis (30.47%) were achieved with the pitched four-bladed impeller and agitation speed of 350–450 rpm, conditions which provided proper balance between requirements for adequate mass/heat transfer and low shear stress. The impact of other process conditions including gluten concentration, temperature, pH and enzyme-gluten ( E / S) ratio on the enzymatic reaction was investigated by applying a Box-Behnken experimental design from the viewpoint of the degree of hydrolysis (DH) and antioxidant activity. Three models obtained allowed calculation of the hydrolysis degree, and both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ABTS (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulpfonic acid) radical scavenging activity from a given set of reaction conditions with good predictability. The statistical analysis showed that each variable had a significant effect on degree of hydrolysis and the antioxidant capacity of both tested systems. Hydrolysis up to around DH 15% improved DPPH radical scavenging activity, while excessive hydrolysis worsened it. The ABTS activity of the hydrolysates was not associated with the DPPH activity nor with the DH, revealing that it was not possible to fulfill all desirable quality requirements (maximum degree of hydrolysis and protein yield, maximum DPPH and ABTS scavenging activities) by using the same reaction conditions. Overall, the study might contribute to approve wheat gluten, a by-product of wheat starch industry, as an accessible and cheap source of bioactive compounds for the development of novel nutraceuticals, cosmetics and drugs. [ABSTRACT FROM AUTHOR]