Ovalbumin Gels Research Articles

Potential Application of Ovalbumin Gel Nanoparticles Loaded with Carvacrol in the Preservation of Fresh Pork.

Plant essential oil has attracted much attention in delaying pork spoilage due to its safety, but its low antibacterial efficiency needs to be solved by encapsulation. Our previous research had fabricated a type of ovalbumin gel nanoparticles loaded with carvacrol (OCGn-2) using the gel-embedding method, which had a high encapsulation rate and antibacterial activity. The main purpose of this study was to further evaluate the stability and slow-release characteristics of OCGn-2 and potential quality effects of the nanoparticles on the preservation of fresh pork pieces during 4 °C storage. The particle test showed that the nanoparticles had better heat stability below 85 °C and salt stability below 90 mM. The in vitro release study indicated that the carvacrol in OCGn-2 followed a Fickian release mechanism. The pork preservation test suggested that the OCGn-2 coating treatments could remarkably restrict the quality decay of pork slices compared to free carvacrol or a physical mixture of ovalbumin and carvacrol treatment. Nano-encapsulation of ovalbumin is beneficial to the sustained release, enhanced oxidation resistance, and improved antibacterial activity of carvacrol. The study suggested that ovalbumin gel nanoparticles embedded with carvacrol could be applied as an efficient bacterial active packaging to extend the storage life of pork.

Rheological and physicochemical properties of heat-induced ovalbumin gels in presence of sodium carboxymethyl cellulose.

In this study, the effect of sodium carboxymethylcellulose (CMC-Na) on the rheological and physicochemical properties of heat-induced ovalbumin (OVA) gels was evaluated. The OVA/CMC-Na composite gels were prepared by heat-induced (85 °C, pH 7.0) a mixture of CMC-Na (0, 0.2, 0.4, 0.8 and 1%) and OVA. The results revealed that the addition of CMC-Na dramatically reduced the springiness and hardness of the composite gels, while slightly enhancing the intermolecular hydrogen bonding interactions, which facilitated the improvement of the softness of the gels. It can be observed by SEM that the added CMC-Na was stacked on the surface of the OVA, resulting in visible "linear bumps". All gel samples exhibited shear-thinning behavior. The apparent viscosity of the composite gels increased with the addition of CMC-Na, and the OVA gel with 1% CMC-Na showed the highest apparent viscosity and the lowest storage modulus (G'). Additionally, low field nuclear magnetic resonance (LF-NMR) measurements indicated that the increasing CMC-Na boosted the water mobility of the composite gel. This study offers a novel approach to the development of ovalbumin-based soft gel foods, especially for certain populations with swallowing difficulties.

Amelioration of ovalbumin gel properties by EGCG via protein aggregation, hydrogen, and van der Waals force.

The mechanism of epigallocatechin gallate (EGCG)-modified ovalbumin gel (EMOG) was investigated. Results indicated that, with the increase of EGCG concentration from 0% to 0.05%, the opacity, hardness, and cohesiveness of EMOG increased significantly from 0.058 to 0.133, 321.0g to 377.6g, and 0.879 to 0.951, respectively, while the soluble protein, surface hydrophobicity, and free sulfhydryl decreased significantly by 41.74%, 28.26%, and 39.36%, respectively. Moreover, EGCG promoted the formation of dense and stable microstructures of EMOG, changed the expansion rate, and improved the stability of EMOG. Moreover, the results of silico simulation showed that EGCG would insert into ovalbumin and interact with the amino acids through van der Waals force and hydrogen bonds, leading to a compact and stable protein structure. In this paper, the mechanism of modification of ovalbumin by EGCG was elucidated at the macro and micro levels, providing insights into the action of polyphenols and proteins.

Combined effects of NaOH, NaCl, and heat on the characteristics of ovalbumin gel and the exploration of the mechanism of transparent gel formation

Salted preserved eggs are made using poultry eggs under the combined action of NaOH, NaCl, and heat. To elucidate the main basis and mechanism of the formation of salted preserved egg white, the effects of NaOH (0.5–2.5%), NaCl (0–1.2%), and heat (72–100 °C) on the properties of ovalbumin (the most abundant protein in poultry egg whites) gel were studied. With increasing NaOH addition, the pH and the absolute value of zeta potential (TAV-ZP) increased, the opacity and Hunter whiteness decreased, and the relaxation time (T2) initially decreased and then increased. With increasing NaCl addition and heating temperature, the pH and TAV-ZP decreased, the opacity and Hunter whiteness increased, and T2 decreased first and then increased. In addition, the hardness and cohesiveness of the ovalbumin gel were greatly modified by NaOH, NaCl, and heat. NaOH contributed to the formation of the gel network structure. In addition, the surface hydrophobicity (H0) analysis result indicated that the tertiary structure of the ovalbumin had changed during the formation of the ovalbumin gel. The correlation analysis results showed that electrostatic repulsion played a vital role in the formation of the transparent ovalbumin gel, and the transparent ovalbumin gel possessed the following characteristics: low aggregation degree, high cross-linking degree, high immobilized water content, gel network structure, and the fully unfolded structure of ovalbumin molecules. In general, the ovalbumin formed a unique gel under the combined action of NaOH, NaCl, and heat. This study could provide theoretical guidance for the processing and control of salted preserved eggs and a reference for highly transparent egg white gel products.

Influence and effect mechanism of disulfide bonds linkages between protein-coated lipid droplets and the protein matrix on the physicochemical properties, microstructure, and protein structure of ovalbumin emulsion gels

In this study, disulfide bonds between the interfacial protein film formed on the lipid particles and the protein in ovalbumin emulsion gels were blocked with 0, 1, 3, 5 and 10 mM of the N-ethylmaleimide (NEM) to explore the influence and effect mechanism of disulfide bonds between the interfacial proteins on the physicochemical properties, microstructure, and protein structure of sunflower oil–ovalbumin emulsion gels. Ovalbumin emulsion gels with NEM-treated ovalbumin emulsion (N-OE) had lower hardness, free sulfhydryl content, water holding capacity (WHC), and surface hydrophobicity, but higher spin−spin relaxation time (T2) than ovalbumin emulsion gels with NEM-treated ovalbumin substrate solution (N-OSS). In addition, N-OE and N-OSS had lower hardness, free sulfhydryl content, WHC and surface hydrophobicity, as well as a more coarse and disordered microstructure than non-NEM treated ovalbumin emulsion gel (control group). The free sulfhydryl content, hardness, WHC, and surface hydrophobicity of the ovalbumin emulsion gels all decreased as the NEM concentration rose (p < 0.05), whereas the amide A band changed to higher wave numbers. These results collectively indicated that the reduction of disulfide between the interfacial layer and the proteins inhibited the hydrophobic effect, the formation of hydrogen bonds, and prevented the formation of larger aggregates. Thus the disulfide bonds between the interfacial proteins contribute to the hardness enhancement and water stabilization of the ovalbumin gel.

Formation of high-elasticity and high-strength semitransparent ovalbumin gel induced by alkali-heat treatment

ABSTRACT The objective of this study was to prepare high-elasticity and high-strength ovalbumin (OVA) gels by comparing the gelling behaviors under the four treatments (alkali-induced, AI; heat-induced, HI; alkali-heat-induced, AHI; and alkali-heat-induced in sequence, AHIS). We measured the secondary structure and investigated the changes in physicochemical properties, intermolecular forces, and water holding capacity (WHC) of the four gels during aging. The AHIS treatment improved the hardness and springiness of the gel; after 1 h of gel formation, the maximum value reached 754.22 ± 46.92 g and 0.96 ± 0.02, respectively. The WHC of the gels also presented a high level, with a maximum value of 88.40 ± 1.20% at 1 h. Although the HI gel had a high hardness value (957.32 ± 51.96 g), it exhibited the lowest elasticity value (0.68 ± 0.03) in 5 h. Meanwhile, the AI gel had low hardness (661.48 ± 32.43 g) and springiness (0.77 ± 0.03) in 5 h. A compact and regular microstructure was formed when the OVA solution was treated with AHIS, meanwhile, the free sulfhydryl (SH) and disulfide bonds (SS) and WHC of the AHIS gel did not change significantly (p > .05), which demonstrated that the gel had formed a stable gel system. Raman spectroscopy showed that AHIS treatment was beneficial to enhance the degree of cross-linking between proteins, the secondary structure changed considerably, the α-helix structure reduced, and the β-structure (β-sheet and β-turn) and random coil increased. Thus, this study provides a new approach to developing high-protein alkaline gel food.

The underlying mechanism of alkali-induced ovalbumin gel transforms to sol: Physicochemical properties, structure and quantitative protein degradation analysis

Different alkalinity could impart certain desirable properties to ovalbumin (OVA), such as improving gel texture or solidification time. In this study, the physicochemical properties, structural changes, and peptide-based quantitative analysis during degradation of OVA treated with 1.25%, 1.5% and 1.75% NaOH solutions at different time were investigated. With the extension of time, the hardness, water holding capacity, particle size, surface hydrophobicity of OVA gel and the number of peptides increased dramatically, and then decreased gradually regardless of alkalinity. By contrast, the pH and springiness of OVA gel exhibited a steady downward trend. Rheological behavior revealed that the OVA gel network degraded from a high viscosity semi-fluid to an aqueous sol. The ordered gel structure was mainly contributed by β-sheets, accompanied by constantly conversion of α-helices, while the liquefaction was caused by the destruction of those regular secondary structures. LC-MS/MS showed that only a small number of common peptides were obtained at different time of protein degradation, and more similar sequences were observed in peptides generated in one day. In summary, it was concluded that although alkali-induced OVA showed a definite gel-sol transformation, the underlying mechanism could not be precisely expressed by degradation into peptides of specific sequences.

Purification of low-abundance lysozyme in egg white via free-flow electrophoresis with gel-filtration chromatography.

As an effective separation tool, free-flow electrophoresis has not been used for purification of low-abundance protein in complex sample matrix. Herein, lysozyme in complex egg white matrix was chosen as the model protein for demonstrating the purification of low-content peptide via an FFE coupled with gel fitration chromatography (GFC). The crude lysozyme in egg while was first separated via free-flow zone electrophoresis (FFZE). After that, the fractions with lysozyme activity were condensed via lyophilization. Thereafter, the condensed fractions were further purified via a GFC of Sephadex G50. In all of the experiments, a special poly(acrylamide- co-acrylic acid) (P(AM-co-AA)) gel electrophoresis and a mass spectrometry were used for identification of lysozyme. The conditions of FFZE were optimized as follows: 130 μL/min sample flow rate, 4.9mL/min background buffer of 20mM pH 5.5 Tris-Acetic acid, 350V, and 14°C as well as 2mg/mL protein content of crude sample. It was found that the purified lysozyme had the purity of 80% and high activity as compared with its crude sample with only 1.4% content and undetectable activity. The recoveries in the first and second separative steps were 65% and 82%, respectively, and the total recovery was about 53.3%. The reasons of low recovery might be induced by diffusion of lysozyme out off P(AM-co-AA) gel and co-removing of high-abundance egg ovalbumin. All these results indicated FFE could be used as alternative tool for purification of target solute with low abundance.

Physicochemical and antibacterial properties of fabricated ovalbumin-carvacrol gel nanoparticles.

The applications of carvacrol are limited due to its poor stability and water solubility, and high volatility; however, ovalbumin can be used to encapsulate hydrophobic molecules, improve their aqueous solubility, and reduce their volatility. In this study, we fabricated ovalbumin-carvacrol nanoparticles (OCGns) under different pH (2, 5, 7, and 9) conditions using a gel embedding method and investigated their physicochemical and antibacterial properties. Rheological experiments revealed that the G' of ovalbumin gels (OGs) prepared under different pH conditions were OG-2 > OG-7 > OG-9 > OG-5. Carvacrol addition reduced the tight structure of ovalbumin and carvacrol under pH 5 and 7 conditions, with hardness first decreasing and then increasing, but increasing under pH 2 and 9 conditions. Fluorescence and infrared spectroscopy indicated complex formation, with carvacrol increasing the average diameter of nanoparticles prepared at pH 2, 5, 7, and 9. Encapsulation reached 89.34 and 91.86% at pH 2 and 9, respectively; however, inhibition experiments revealed that the minimum inhibitory concentration of OCGn-2 against Gram-positive Bacillus cereus and Salmonella (0.08 and 0.16 mg mL-1, respectively) was lower than that of OCGn-9 (both 0.28 mg mL-1). Moreover, OCGn-2 possessed a better dense gel structure and a higher stability, encapsulation rate, and antibacterial activity, suggesting that pH affects gel microstructure and thus the encapsulation efficiency and bacteriostatic properties of the prepared nanoparticles. These results contribute to our knowledge of the design and fabrication of polymeric nanoparticle delivery systems for bioactive compounds with beneficial properties.

Temperature-dependent near-infrared spectroscopy for studying the interactions in protein aqueous solutions

Temperature-dependent near-infrared spectroscopy has been developed for studying quantitative and structural analysis, as well as the molecular interactions. Taking the advantage of the temperature effect on hydrogen bonding, the technique has shown its potential in analyzing the interactions in aqueous solutions. In our recent studies, the structural changes in homo-oligopeptides K5 (penta-lysine), D5 (penta-aspartic acid), and protein (ovalbumin) aqueous solutions were studied by temperature-dependent near-infrared spectroscopy. The thermodynamics and their interaction with water were analyzed with the help of the chemometric methods including continuous wavelet transform, independent component analysis, two-dimensional (2D) correlation analysis, and Gaussian fitting. The results show that the oligopeptide in aqueous solution improves the thermal stability of the water species, and K5 has stronger interaction with water than D5. In the gelation of ovalbumin, the change of the water species with two hydrogen bonds (S2) follows the same phases as the protein. S2 maintains the stability of the protein in native and molten globule states, and the weakening of the hydrogen bond in S2 by high temperature results in the destruction of the hydration shell and makes the ovalbumin clusters form a gel structure.

Formation mechanism of ovalbumin gel induced by alkali

In this paper, the alkali-induced gelling behavior of ovalbumin, including its microstructure characteristics, intermolecular forces, and molecular structure changes, was investigated. The results showed that ovalbumin formed a three-dimensional gel with an ordered fibrous mesh structure under alkali conditions. The active force between gel molecules was maintained by a large number of ionic bonds (∼85%), a small number of disulfide bonds (∼5%), and very few hydrophobic interactions and hydrogen bonds. SDS-PAGE analysis showed that ovalbumin formed aggregates via ionic and disulfide bonds. ANS fluorescence spectroscopy analysis showed that strong alkali caused rapid denaturation of ovalbumin molecules to expose the hydrophobic core, thus greatly increasing the surface hydrophobicity. However, the hydrophobicity decreased during the gelation stage. FTIR analysis showed that strong alkali induced the secondary-level structure of ovalbumin molecules to interconvert, and most of them existed in a relatively stable α-folding structure. Endogenous fluorescence and UV spectroscopic analyses showed that the amino acid residues of ovalbumin in the gelation stage moved towards the polar environment. It was concluded that the secondary and tertiary structures of ovalbumin changed after treatment with strong alkali and that a crystal gel formed through the action of ionic and disulfide bonds. In addition, the long-term action of strong alkali gradually decreased the gelatinous property.

Activation energy of the disruption of gel networks in relation to elastically stored energy in fine-stranded ovalbumin gels

The aim of this study was to relate the activation energy of the disruption of ovalbumin networks to elastically stored energy (i.e. recoverable energy, RE) obtained from mechanical deformation tests. To this end, heat-set ovalbumin gels were prepared at a fixed volume fraction and pH, but varying incubation temperatures. The activation energy required to disrupt the gels was derived from the Arrhenius equation. Increasing incubation temperature from 65 to 95 °C during gel formation resulted in a gradual increase in the activation energy up to a factor of ∼8. Gels obtained at or just below the protein denaturation temperature of around 75 °C had significantly lower recoverable energy (RE). These latter gels also had lower fracture stress and strain. At incubation temperatures above 70 °C RE was constant around 75%, although a steady increase in activation energy was observed. This demonstrates that storing energy in a protein network is not directly related to the interactions that make up the network. A combination of electron microscopy, water holding, and stress relaxation experiments were performed to study the different energy dissipation modes. It was shown that different dissipation modes for various gels were comparable, and this explains why the RE was similar, with the exception of gels prepared at lower incubation temperatures where (micro) fracture events could have occurred that lowered the RE. These results suggest that RE is not a network characteristic related to microstructural or smaller length scale interactions, but the result of various material-related energy dissipation mechanisms.

Relating water holding of ovalbumin gels to aggregate structure

To increase understanding of water holding in heat-set ovalbumin gels, the relation between aggregate structure (both in solution and in gels) and gel coarseness or gel stiffness is studied. The aggregate morphology obtained by preparation of ovalbumin gels between pH 5.8 and 6.8 differs, as shown by a combination of light scattering, confocal microscopy, electron microscopy and neutron scattering techniques. It is shown that with decreasing pH larger aggregates are formed that are more compact, indicated by the fractal dimension that increased from 1.9 to 2.6. Furthermore, larger, more compact aggregates at pH 5.8 as compared to pH 6.8 resulted in more coarse gels with a less merged microstructures. In addition, a lower gel stiffness is observed at lower pH. The combination of a higher coarseness and lower gel stiffness explains both the lower total water holding and the easier exudation of water from the gel upon applied forces.

Effect of Fish Water Soluble Protein Concentrate on the Formation of Fatty Acid Salt-Induced Gel of Ovalbumin

Effect of Fish Water Soluble Protein Concentrate on the Formation of Fatty Acid Salt-Induced Gel of Ovalbumin

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加熱誘導卵白アルブミンゲルの形成に及ぼす乳&lt;i&gt;α&lt;/i&gt;-カゼインおよびカプリン酸ナトリウム添加の影響

Study on the dissolution of heat-induced ovalbumin gel in alkaline solutions relevant to the removal of fouling deposits

Heat-induced whey protein concentrate gels (HIWPCG) have previously been used to simulate milk fouling and cleaning processes. The related research has generated considerable knowledge, which is of practical interest. In the current study, heat-induced ovalbumin gels (HIOVAG) have been employed to investigate the dissolution process (related to chemical cleaning process). Both HIOVAG and HIWPCG are sensitive to NaOH solution, which is a common cleaning fluid in food industry. In contrast to the HIWPCG behavior, HIOVAG dissolution presents no optimal NaOH concentration where the rate of dissolution is highest. The dissolution temperature was found to positively influence the dissolution process of HIOVAG, i.e. the dissolution rate increased with increasing dissolution temperature. In addition, ovalbumin (OVA) concentration in HIOVAG was found to be another important factor influencing the dissolution process. However, the stirring speed (convection) and heating time had no effect in the range tested, indicating that the process was internally limited.

Microbial transglutaminase-mediated modification of ovalbumin

In the present paper we have investigated the impact of microbial transglutaminase on thermally treated ovalbumin. In fact, ovalbumin was modified by microbial transglutaminase following heat treatment for 1 h at 80 °C. The protein was both intra- and inter-molecularly crosslinked as shown by the formation of high molecular weight polymers and a monomer having similar molecular weight but higher electrophoretic mobility when compared to unmodified ovalbumin. Analysis of simulated digestion under physiological conditions has demonstrated that the biopolymers obtained after transglutaminase treatment were more resistant to both gastric and duodenal digestion. Whilst they started gradually being digested after 5 min of incubation with pepsin, some of them were still present even after 60 min incubation with the duodenal enzymes, trypsin and chymotrypsin. Furthermore, incubation of 1.5% (w/v) ovalbumin gel in the presence of transglutaminase led to the formation of a well-developed viscoelastic gel network with higher modulus and lower phase angle values. These results suggest a possible use of transglutaminase-modified ovalbumin in the food industry as a potential ingredient to enhance both the functional properties of many food-based products, such as digestibility, and mechanical properties, such as viscoelasticity and gel strength.

Mechanical Properties of Ovalbumin Gels Formed at Different Conditions of Concentration, Ionic Strength, pH, and Aging Time

Ovalbumin gels were prepared by heat treatment at constant pH and ionic forces. Ovalbumins are widely utilized as emulsifying or binding agents. However, due to their protein origin, mechanical properties of ovalbumins are enclosed in a wide range of rheological responses depending on concentration, ionic strength, pH, and aging time. The objective of this work was to study the effect of processing conditions (pH, ionic strength, and protein content) on the textural attributes of an ovalbumin protein system by means of uniaxial compression. Gels were prepared by dispersing proteins (purity 98%) (8.3–12.5% w/w) until complete dissolution in deionized water at 90°C by 45 min, pH (6.3–9.1) was adjusted using citric acid, and the ionic strength (0–100 mM of NaCl) was adjusted using NaCl. The storage of gels was done at 63°C (24–168 h). The rheological tests of gels were done by uniaxial compression. A rupture force peak was observed at high protein content together with an increase in the Young’s modulus. At fixed conditions of ion content (NaCl 50 mM) and pH of 7, the gels presented a maximum in fracture force and Young's modulus after 7 days of storage. The addition of minimum amount of citric acid increases the stability of ovalbumin gels. This information is useful to ensure that the final product will remain stable during storage time at longer shelf lives.

Studies of ovalbumin gelation in the presence of carrageenans and after manothermosonication treatments

Ovalbumin is a key ingredient in many food products due to its ability to form a three-dimensional network after heat denaturation, that is, to form gels. We have explored two ways of modifying gels based on ovalbumin: (1) the addition of carrageenans, and (2) manothermosonication (MTS) treatments of ovalbumin suspensions prior to gelation. Ovalbumin gels showed elastic modulus ( G ′) values of 1216 Pa after a heating and a cooling period. The addition of kappa, lambda, and iota carrageenan enhanced G ′ values by 6, 1.7, and 1.7 fold, respectively. Kappa carrageenan was not only the most effective carrageenan in the improvement of ovalbumin gelation but changed also the gelation process at the end of the cooling phase. MTS treatments reduced G ′ values of ovalbumin gels by about 50% measured immediately after MTS treatments but only by ca. 25% after 24 h, which reveals that ovalbumin modifications introduced by ultrasound, whatever they are, are reversible. This reduction does not preclude the use of manothermosonicated liquid egg as gelling agent.

Synthesis of Nanocrystalline Alumina Using Egg White

A new simplified route to prepare nanocrystalline alumina powders is proposed. The method involved the use of freshly extracted egg white (ovalbumin) and aluminum nitrate in an aqueous medium. Changes in ionic strength upon addition of aluminum nitrate resulted in gelation of ovalbumin. The added metal ions were dispersed in the gelled ovalbumin matrix. Heat treatment of the gelled mass resulted in nanosized γ alumina at as low a temperature as 330°C. TEM analysis showed that the particle size ranged from 15 to 80 nm.