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This study prepared emulsion gels by modifying ovalbumin (OVA)-flaxseed oil (FSO) emulsions with transglutaminase (TGase) and investigated their properties, structure and oxidative stability under different enzyme reaction times. Here, we found prolonged reaction times led to the transformation of α-helix and β-turn into β-sheet and random coil. The elasticity, hardness and water retention of the emulsion gels increased significantly, but the water-holding capacity decreased when the reaction time exceeded 4 h. Confocal laser scanning microscope (CLSM) indicated extended enzyme reaction time fostered oil droplet aggregation with proteins. Emulsion gel reduced FSO oxidation, especially after 4 h of the enzyme reaction, the peroxide value (PV) of the emulsion gel was reduced by 29.16% compared to the control. In summary, the enzyme reaction time of 4 h resulted in the formation of a dense gel structure and enhanced oxidative stability. This study provides the potential applications in functional foods and biomedical fields., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In this study, we evaluated potential usage of acylated ovalbumin (AOVA) nanogels fabricated via acylation modification and heat-induced self-assembly process as novel delivery systems for curcumin. Compared to native ovalbumin (NOVA) nanogels without chemical acylation, the obtained AOVA nanogels have shown smaller average hydrodynamic diameter (155.73 nm), relatively uniform size distribution (polydispersity index around 0.28), enhanced negative surface charge (-24.3 mV), and an improved stability under the conditions of high ionic strength, different pH and storage time. Moreover, AOVA nanogels exhibited a remarkable conformational change in secondary and tertiary structures, improved surface hydrophobicity, and increased free sulfhydryl content compared with NOVA nanogels. Moreover, curcumin encapsulated in AOVA nanogels displayed higher encapsulation efficiency (93.64%) and slower sustained release under simulated gastrointestinal conditions as compared with NOVA nanogels. Hence, we have suggested that AOVA nanogels successfully fabricated with improved physicochemical properties as a novel ideal carrier for hydrophobic active compounds., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In addition to small amounts of minerals and carbohydrates, most of the dry matter of chicken egg white is protein, making egg white an ideal resource for obtaining food proteins. Ovalbumin (OVA), which accounts for more than 50% of the total egg white protein, is one of the most widely studied food proteins due to its multiple functional properties, and it has also been used as a model protein molecule in many research fields. The objective of this study was to develop a simple and rapid method for the purification of OVA from egg whites on large scale. First, OVA was separated from ovomucin, ovotransferrin, and ovomucoid by polyethylene glycol (PEG) concentration, using the following optimal parameters: the PEG concentration was 15%, the pH was 6.5, the salt concentration was 100 mmol/L, and the operating temperature was 10°C. The OVA-rich supernatant obtained from PEG precipitation was further purified by isoelectric precipitation at a pI of 4.5 and a temperature of 4°C, and the purified OVA was obtained with at a purity of 95.1% by HPLC, with a yield of 46.4%. After the extraction of OVA, the PEG solution was vacuum dried and then utilized cyclically in the PEG precipitation steps. The whole purification process could be finished within 2 to 3 h at a scale of several kilograms of egg white. This method has the advantages of rapidity, simplicity, low cost, and ease of scalability., (© 2018 Poultry Science Association Inc.)

As the most abundant protein in chicken eggs, ovalbumin plays an important role in the processing of high value-added poultry products. The present study investigated the effects of hydroxyl radical-induced early stage oxidation on the physicochemical and interfacial properties of chicken egg white ovalbumin. Protein carbonyl content of ovalbumin increased (from 0.78 to 1.13 nmol/mg) with the oxidation time (0-5 h), while free sulfhydryl content (from 0.43 to 0.09 nmol/mg) and free amino group content (from 0.49 to 0.43 nmol/mg) decreased. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis showed that the exposure of ovalbumin to hydroxyl radicals caused self-cross-linking and resulted in the formation of dimers and trimers. Accompanied by these changes, the surface hydrophobicity of ovalbumin was enhanced about 1.5-fold with the deepening of oxidation, and the value of zeta potential became more negative (from -7.15 to -20.51 mv). About 2 h of moderate oxidation improved the foaming and emulsifying properties of ovalbumin (1.2-fold to 1.8-fold), while excessive oxidation (3 h) decreased these interface properties. Hydroxyl radical-induced oxidation changed the surface chemical groups and structures of ovalbumin, thereby affecting the surface properties. The foaming and emulsifying properties of ovalbumin could be improved by oxidation, increasing the application possibilities of ovalbumin in the food interface system., (© 2018 Poultry Science Association Inc.)

An efficient one-step grafting approach was developed to modify ovalbumin (OVA) by phosphorylation through selective reaction with the hydroxyl group of Ser and Thr residues present in OVA. The site-specific phosphorylated conjugates were characterized by Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF/MS) and the results indicated that the Ser residue could be more readily phosphorylated, and the typical phosphopeptides 264 LTEWTSSNVMEER 276 and 340 EVVGSAEAGVDAASVSEEFR 359 demonstrated the formation of monophosphoester. Moreover, 13 C NMR analysis showed that the βCH 2 of Ser acted as a hydroxyl donor to react with sodium tripolyphosphate (STPP), and the conjugates with variable phosphorylation sites could improve the weak network and the resulting poor mechanical properties of ovalbumin-based hydrogels. Furthermore, small-amplitude oscillatory measurements, creep recovery tests and texture profile analysis of hardness and stickiness indicated that phosphorylation can strengthen the intermolecular cross-linking of protein molecules and produce significant influence on the rheological behavior and texture properties, suggesting that a suitable conjugation site is essential for the best gelation properties at a different pH. The integrated results indicate that phosphorylation change significantly modify the viscoelastic and mechanical properties of OVA-based hydrogels by changing molecular dynamics upon heating., (Copyright © 2017 Elsevier B.V. All rights reserved.)

To improve the interfacial properties, a phosphorylation modification of OVA was performed through dry-heating at three different pH values (5.0, 7.0 and 9.0) in the presence of sodium tripolyphosphate. X-ray photoelectron and Raman spectroscopies confirmed that phosphate groups were successfully grafted onto the ovalbumin backbone through covalent interaction to form OP bond. Additionally, 23, 21 and 18 phosphorylation sites were identified in the OVA that had been phosphorylated at pH 5.0, 7.0 and 9.0 (P-OVA5, P-OVA7 and P-OVA9) respectively by MALDI-TOF mass spectroscopy. More phosphorylated peptides and possible phosphorylation sites were found here than in previous studies with the reaction time reduced to 12h. As a result, the iso-electric point (pI) of P-OVA shifted to lower pH, improving the stability of the P-OVA-included system over a wider pH range. The dynamic interfacial tension, which depends on the phosphorylation-induced conformational change, was explored by Fourier-transform Raman and circular dichroism spectroscopies, and the equilibrium interfacial tension decreased from 17.359mNm -1 for natural OVA (N-OVA) to 15.969mNm -1 for P-OVA9. Furthermore, P-OVA was applied to O/W emulsions, resulting in a narrower size distribution with a smaller particle size in P-OVA-stabilized emulsions than in N-OVA-stabilized emulsions. The increase rate of mean particle diameter after 60-min storage decreased from 72.37% for N-OVA to 7.97% for P-OVA5, implying a significant improvement of emulsion stability by preventing aggregation and coalescence. The results from this work demonstrated that the natural biopolymer can be applied to O/W emulsions by enhancing interfacial properties with phosphorylation., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In this study, ovalbumin (OVA) was succinylated with the addition of different levels of succinic anhydride, and the structural and functional properties of succinylated OVA (SOVA) were investigated. SDS−PAGE and FTIR spectrum confirmed the covalent attachment of the succinyl group to OVA. Thermal stability and the absolute value of zeta potential (pH 6.0) of SOVA were enhanced by 14.90% and 76.77% higher than that of the native OVA (NOVA), respectively. Circular dichroism (CD) spectra demonstrated that the succinylation decreased the α−helix and increased β−sheet content to 21.31% and 43.28%, respectively. The content of free sulfhydryl groups increased and intrinsic fluorescence spectra suggested the SOVA became more unfolded and flexible as the degree of succinylation enhanced. Furthermore, succinylation effectively enhanced the solubility and decreased the interface tension (oil−water and air−water interface) of OVA. Compared to NOVA, the emulsifying activity and stability of SOVA were increased by 1.6 times and 1.2 times, respectively, and foaming capacity and stability were enhanced by 2.7 times and 1.5 times, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acylation of OVA significantly improved the gel properties of hydrogels. • Acylation modification effectively promoted the formation of network structures in OVA hydrogels. • Acylation modification effectively enhanced hydrophobic interactions during thermal gelation. • Acylated OVA hydrogels exhibited a delayed drug release of curcumin. In this paper, the effects of acylation modification on the gel behavior of ovalbumin (OVA) under heating induction have been investigated. From the obtained results, the acylated OVA hydrogels exhibited superior gelation properties than the native OVA hydrogels (NOVA-G) in terms of light transmission, gel hardness, resilience and water holding capacity. SEM revealed acylation modifications effectively promoted the formation of uniform and dense network structure of OVA hydrogels. The main intermolecular forces of the acylation-modified OVA hydrogels were hydrophobic interactions and hydrogen bonding. FTIR showed that acylation modifications caused 26.2% decrease in α-helix and 59.2% increase in β-sheet content compared to NOVA-G. Furthermore, in-vitro release experiments showed that the release rate of curcumin from acylated OVA hydrogels was significantly delayed. Moreover, the above results have shown that acylation modifications can be considered as an effective method to improve the gelation as well as drug release properties of protein hydrogels. [ABSTRACT FROM AUTHOR]

As two major proteins of egg white, the interaction between lysozyme (LYZ) and ovalbumin (OVA) has been studied. In the present research, the mechanism and kinetics of the interaction between LYZ and OVA were studied using several methods, including cyclic voltammetry (CV), dual polarization interferometry (DPI) and surface plasmon resonance (SPR), and the effect of their interaction on the activity of LYZ was investigated using a bacteriolytic activity assay. Cyclic voltammograms showed that there was an interaction between these two proteins. DPI results indicated that the interaction is a type of chimeric mode, and the K A and K D of the interaction were 498 and 2.01 × 10−3 mol/L, respectively, calculated from the fitting of the surface plasmon resonance curve. The bacteriolytic activity assay showed that the interaction between these two proteins reduced the bacteriolytic activity of LYZ. [ABSTRACT FROM AUTHOR]

In this work, ovalbumin (OVA) was phosphorylated by dry-heating at three different pH values (5.0, 7.0 and 9.0) and 45 °C for 12 h in the presence of sodium tripolyphosphate (STP). The results indicated that, when compared with native OVA (N-OVA), the zeta potential absolute value of phosphorylated OVA (PP-OVA) increased from 2.13 mv (N-OVA) to 13.57(PP-OVA-pH5.0), 16.00(PP-OVA-pH 7.0) and 11.20 mv (PP-OVA-pH 9.0); the volume-weighted mean diameter (D [4,3])of emulsions stabilized by the N- and PP-OVA decreased from 70.22 μm (N-OVA) to 37.16(PP-OVA-pH 5.0), 16.21(PP-OVA-pH 7.0) and 43.52 μm (PP-OVA-pH 9.0); and PP-OVA emulsions exhibited a more narrow monomodal size distribution and a smaller particle size than those of N-OVA, with the corresponding emulsifying activities index (EAI) increased from 92.71(N-OVA) to 142.51(PP-OVA-pH5.0), 224.88(PP-OVA-pH 7.0), and 150.97(PP-OVA-pH 9.0), respectively. The microscopic observation showed that the emulsion droplets of PP-OVA were more densely and uniformly distributed than those of N-OVA. Furthermore, characterization of PP-OVA by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and 31 P nuclear magnetic resonance ( 31 P NMR) revealed that phosphate groups were bound to the -OH on serine and threonine and the -NH 2 on lysine and arginine, with covalent interactions (C–O–P and C-N-P bounds) formed between OVA and STP. This study demonstrated that the introduction of phosphate groups could increase the amount of negative charge and intermolecular repulsion, decrease the particle size of droplets and improve the emulsifying ability of PP-OVA. [ABSTRACT FROM AUTHOR]

Abstract In this study, ovalbumin (OVA) was phosphorylated under wet-heating in the presence of sodium tripolyphosphate at pH 6.0 and 60 °C for 1, 2, 3, 4 and 5 h, and the structural and physical properties of phosphorylated OVA (P-OVA) were investigated. The FT-IR spectrum confirmed the covalent attachment of the phosphate group to OVA. New possible phosphate sites (Ser-221, Ser-269, Tyr-281 and Ser-324) were detected by using liquid chromatography in tandem with mass spectrometry. Circular dichroism (CD) spectra demonstrated that P-OVA molecular became more flexible and disordered. The decreased fluorescence intensity indicated that the chromophore microenvironment became more exposed and polar because of conformational changes. The surface hydrophobicity (H 0) and the absolute value of zeta potential of P-OVA obtained at 5 h was 1.8 and 1.5 times higher than that of N-OVA. Foaming ability (FA) and foaming stability (FS) were enhanced by 1.7 and 4.4 times after wet-heating phosphorylation for 4 h, which were up to 87.0% and 28.5%, respectively. Furthermore, the correlation analysis suggested that FA was significantly correlated to random structure (P < 0.01) and H 0 (P < 0.01), and zeta potential was related with FS (P < 0.05). Graphical abstract Image 102 Highlights • Ovalbumin was phosphorylated by sodium tripolyphosphate under wet-heating. • Possible phosphate sites were detected by LC-MS/MS. • Structural changes were confirmed by fluorescence and CD spectrum. • H 0 and the absolute value of zeta potential increased after the phosphorylation. • Foaming ability and stability were promoted by phosphorylation. [ABSTRACT FROM AUTHOR]

Fluorescence resonance energy transfer (FRET), a near-field energy transfer from a fluorescent donor to a fluorescent acceptor within close proximity, has been widely used in biosensing. In this study, a rapid and universal sensor for the detection of ovalbumin (OVA) using nitrogen, oxygen, phosphoric co-doped CDs (NOP-CDs) and graphene oxide (GO) was established based on the FRET technology. First, novel NOP-CDs peak at 443 nm were synthesized by a one-pot hydrothermal method using egg powder and phosphorus acid. Then, in the absence of OVA, the fluorescence of OVA-antibody modified NOP-CDs was quenched by GO via electrostatic attraction and π-π stacking interaction due to the FRET effect. The introduced OVA competed to displace the GO by special binding with the anti-OVA, resulting in the recovery of the fluorescence. This sensor displayed a linear response to OVA from 0.5 to 15 μg/mL with a detection limit of 153 ng/mL and was successfully applied to the detection of the OVA sample with recoveries ranging from 99.25 to 118.90%. In summary, the green and easy-to-synthesize nano-material was used in this method, the accurate detection results, and the simple process exhibited the great potential of this method for practical applications. [ABSTRACT FROM AUTHOR]

During the egg storage, the change in structure of ovalbumin (OVA) was determined by spectroscopy of Fluorescence, Circular Dichroism and Fourier-Transform Raman. The relationships between the OVA properties and structure were also investigated in this study. Comparing with the consequence of Circular Dichroism and Fourier-Transform Raman spectra, it was obvious that the percentage of α-helix and β-sheet showed downward trends after storage. In contrast, the percentage of β-turn and random coil clearly presented raising trend. Furthermore, tryptophan residues were buried in a more hydrophobic environment. The emulsifying and foaming properties of OVA all decreased during the storage. Moreover, the correlation analysis indicated that β-sheet related to the emulsifying stability of OVA ( p < 0.01), α-helix related to the foaming stability ( p < 0.05) at the same time. This study provided new interesting idea for the study on the relationships between the structure and functional properties of protein during food storage. [ABSTRACT FROM AUTHOR]

Abstract: Obtaining several proteins from chicken egg whites from a single extraction in a continuous process is imperative because there are potential applications for egg white proteins in the pharmaceutical and food industries. In this study, chicken egg whites were divided into four components using polyethylene glycol precipitation. All precipitates, except for ovomucin (Precipitate A), were further purified through Q Sepharose Fast Flow anion-exchange chromatography. Lysozyme, ovotransferrin, ovalbumin and ovoflavoprotein were purified from Precipitate B, Precipitate C and Supernatant D, respectively, which were determined to be 91.84%, 94.55%, 96.45% and 88.16% pure, respectively, by HPLC. The results showed that this method is feasible for the co-purification of major egg white proteins with high purity. This method is scientifically practical and easy to use and thus will suitable for industrial-scale production. [Copyright &y& Elsevier]

The aim of this research was to synthesize ovalbumin-pullulan conjugates through the Maillard reaction and compare the molecular characteristics of native ovalbumin (N-OVA), heated ovalbumin (H-OVA) and glycosylated ovalbumin (G-OVA). The glycosylation was monitored by the degree of graft and Amadori compound. Covalent binding between ovalbumin and pullulan was confirmed by SDS-PAGE and FTIR. CD spectra showed that glycosylation could inhibit the heat-induced formation of β-sheet. Due to the shielding effect of polysaccharide, H 0 and fluorescence intensity of G-OVA were lower than those of heated group. Meanwhile, zeta potential values of G-OVA at three different pH were extreme small, close to zero. Compare with N-OVA, the free exposed sulfhydryl contents of conjugates increased and total free sulfhydryl contents decreased. For G-OVA, foaming stability was 50.5%, which was a factor of 7.1 higher than the value of N-OVA (7.1%). G-OVA foam displayed smaller and more homogeneous bubble size than N-OVA and H-OVA. In addition, G-OVA foam presented the slowest rate of the bubble size increase over time. Overall, Maillard reaction was proven to be successful in enhancing the foaming properties of ovalbumin. Image 1 • Pullulan was conjugated to ovalbumin using Maillard reaction. • SDS-PAGE and FTIR confirmed the covalent attachment of ovalbumin to pullulan. • Pullulan bound to albumin covered the surface of the globular ovalbumin. • Foaming stability was enhanced by glycosylation. [ABSTRACT FROM AUTHOR]