Gel properties of heat-induced transparent hydrogels from ovalbumin by acylation modifications

Ultrasonic-microwave technique promotes the physicochemical structure of hydrogel and its release characterization of curcumin in vitro

In this study, soybean protein isolate and hawthorn pectin were mixed to prepare binary hydrogels using ultrasound and microwave techniques. Moderate treatment can not only significantly improve the mechanical strength of the hydrogel, but also increase the tightness of the internal cross-linking. The strengthening of interactions (hydrogen bonds, hydrophobic interactions, and disulfide bonds) was the main reason for this trend. Especially, the ultrasonic-microwave (80 s) treatment hydrogel possessed excellent hardness (33.426 N), water-holding capacity (98.26%), elasticity (G' = 1205 Pa), and a more homogeneous and denser microstructure. In addition, the hydrogel minimized the extent of curcumin loss (21.23%) after 5 weeks of storage. In general, the ultrasonic-microwave technique could significantly promote the physicochemical structure and curcumin bioaccessibility of hydrogels, which showed excellent market prospects in the food industry.

Transglutaminase cross-linking ovalbumin-flaxseed oil emulsion gels: Properties, microstructure, and performance in oxidative stability

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.

Formation mechanism, environmental sensitivity and functional characteristics of succinylated ovalbumin/ε-polylysine electrostatic complexes: The roles of succinylation modification and ε-polylysine combination

Biocomplex materials formed by oppositely charged biopolymers (proteins) tend to be sensitive to environmental conditions and may lose part functional properties of original proteins, and one of the approaches to address these weaknesses is protein modification. This study established an electrostatic composite system using succinylated ovalbumin (SOVA) and ε-polylysine (ε-PL) and investigated the impact of varying degrees of succinylation and ε-PL addition on microstructure, environmental responsiveness and functional properties. Molecular docking illustrated that the most favorable binding conformation was that ε-PL binds to OVA groove, which was contributed by the multi‑hydrogen bonding and hydrophobic interactions. Transmission electron microscopy observed that SOVA/ε-PL had a compact spherical structure with 100 nm. High-degree succinylation reduced complex sensitivity to heat, ionic strength, and pH changes. ε-PL improved the gel strength and antibacterial properties of SOVA. The study suggests possible uses of SOVA/ε-PL complex as multifunctional protein complex systems in the field of food additives.

Age Gelation in Direct Steam Infusion Ultra-High-Temperature Milk: Different Heat Treatments Produce Different Gels

To investigate the gelation process of direct ultra-high-temperature (UHT) milk, a pilot-scale steam infusion heat treatment was used to process milk samples over a wide temperature of 142-157 °C for 0.116-6 s, followed by storage at 4 °C, 25 °C, and 37 °C. The results of the physicochemical properties of milk showed that the particle sizes and plasmin activities of all milk samples increased during storage at 25 °C, but age gelation only occurred in three treated samples, 147 °C/6 s, 142 °C/6 s, and 142 °C/3 s, which all had lower plasmin activities. Furthermore, the properties of formed gels were further compared and analyzed by the measures of structure and intermolecular interaction. The results showed that the gel formed in the 147 °C/6 s-treated milk with a higher C* value had a denser network structure and higher gel strength, while the 142 °C/6 s-treated milk had the highest porosity. Furthermore, disulfide bonds were the largest contributor to the gel structure, and there were significant differences in disulfide bonds, hydrophobic interaction forces, hydrogen bonds, and electrostatic force among the gels. Our results showed that the occurrence of gel was not related to the thermal load, and the different direct UHT treatments produced different age gels in the milk.

Mechanically Tough and Conductive Hydrogels Based on Gelatin and Z-Gln-Gly Generated by Microbial Transglutaminase

Gelatin-based hydrogels with excellent mechanical properties and conductivities are desirable, but their fabrication is challenging. In this work, an innovative approach for the preparation of gelatin-based conductive hydrogels is presented that improves the mechanical and conductive properties of hydrogels by integrating Z-Gln-Gly into gelatin polymers via enzymatic crosslinking. In these hydrogels (Gel-TG-ZQG), dynamic π-π stacking interactions are created by the introduction of carbobenzoxy groups, which can increase the elasticity and toughness of the hydrogel and improve the conductivity sensitivity by forming effective electronic pathways. Moreover, the mechanical properties and conductivity of the obtained hydrogel can be controlled by tuning the molar ratio of Z-Gln-Gly to the primary amino groups in gelatin. The hydrogel with the optimal mechanical properties (Gel-TG-ZQG (0.25)) exhibits a high storage modulus, compressive strength, tensile strength, and elongation at break of 7.8 MPa at 10 °C, 0.15 MPa at 80% strain, 0.343 MPa, and 218.30%, respectively. The obtained Gel-TG-ZQG (0.25) strain sensor exhibits a short response/recovery time (260.37 ms/130.02 ms) and high sensitivity (0.138 kPa-1) in small pressure ranges (0-2.3 kPa). The Gel-TG-ZQG (0.25) hydrogel-based sensors can detect full-range human activities, such as swallowing, fist clenching, knee bending and finger pressing, with high sensitivity and stability, yielding highly reproducible and repeatable sensor responses. Additionally, the Gel-TG-ZQG hydrogels are noncytotoxic. All the results demonstrate that the Gel-TG-ZQG hydrogel has potential as a biosensor for wearable devices and health-monitoring systems.

Ultra-stable pickering emulsion stabilized by anisotropic pea protein isolate-fucoidan conjugate particles through Maillard reaction

Bio-based emulsifiers hold significant importance in various industries, particularly in food, cosmetics, pharmaceuticals and other related fields. In this study, pea protein isolate (PPI) and fucoidan (FUD) were conjugated via the Maillard reaction, which is considered safe and widely used in the preparation of food particle. The PPI-FUD conjugated particles exhibit an anisotropic non-spherical structure, thereby possessing a high detachment energy capable of preventing emulsion coalescence and Ostwald ripening. Compared to emulsions previously prepared in other studies (< 500 mM), the Pickering emulsion stabilized by PPI-FUD conjugate particles demonstrates outstanding ionic strength resistance (up to 5000 mM). Furthermore, when encapsulating curcumin, the Pickering emulsion protects the curcumin from oxidation. Additionally, the formulated emulsions demonstrated the capability to incorporate up to 60 % (v/v) oil phase, revealing remarkable performance in terms of storage stability, pH stability, and thermal stability.

Enhanced emulsification performance and interfacial properties of Janus-like rapeseed cruciferin through asymmetric acylation modification

Plant protein emulsifiers, particularly rapeseed protein isolate with its superior amino acid composition and predominantly globular protein, have captured significant interest in the food industry. Nonetheless, the application of these proteins has been stymied by their lackluster emulsification properties. Addressing this challenge, our study implements an innovative asymmetric acylation technique to modify the surface of rapeseed cruciferin (RC), morphing it into a structure resembling Janus nanoparticles. This alteration amplifies the emulsification prowess of RC by a remarkable 2.7 times compared to its natural form, and 1.43 times over its conventionally acylated counterpart. The asymmetrically acylated RC, marked by a distinctive three-phase contact angle of 90.4°, manifests an outstanding amphiphilic character. Moreover, it surpasses both the natural and conventionally acylated RC in terms of diffusion, penetration, and rearrangement rates, as well as protein concentration at the oil-water interface. Compared to commonly used emulsifiers in the food industry, such as lecithin and soy protein, the asymmetrically acylated RC stands out, stabilizing emulsions with the tiniest particle size and effectively staving off emulsion stratification over a longer duration. This study underscores that asymmetric acylation serves as a reliable methodology for producing efficient plant protein emulsifiers, considerably amplifying their utility in the food industry.

New insight into yolk sphere microgel structure impacted by lipid and protein distribution changing under heating processing

The gel structure of boiled, shelled egg yolk is formed by the accumulation of yolk spheres, which are rich in lipids and proteins, and investigating the properties of the lipid-protein complex gel structure of the yolk sphere under heating is important. In this study, we used SEM and CLSM to confirm lipid migration and protein aggregation. We observed that during the heating process, the thermal stability decreased, and there was an increase in the content of β-turns and the degrees of freedom of water and lipids. G' increased during the frequency sweep but decreased after heating for 120 min. The various yolk gel structures exhibited varying degrees of resistance to compression from external forces. Prolonged heating resulted in the presence of gaps and increased surface roughness of the spheres. In conclusion, heating induced lipid migration and protein aggregation in the sphere microgels, thereby altering the structural properties of the gels.

Translucency mechanism of heat-induced pigeon egg white gel

In this study, the properties of pigeon egg white (PEW) and chicken egg white (CEW) thermal gels were compared, with the aim of revealing the mechanisms involved in the high transparency of PEW thermal gels. Results demonstrated that PEW gels exhibited higher transparency than CEW gels. Scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis revealed that PEW gels formed a fine chain gel network structure with an average diameter of thermal aggregates (89.84 ± 7.13 nm). The molecular properties of PEW proteins, such as higher content of β-sheet structures (32.73 %), reactive groups (free sulfhydryl groups, hydrophobic groups), and absolute zeta potential (-3.563 mV), were found to contribute to the formation of smaller thermal aggregates during thermal denaturation. The microrheology measurements showed that these features allowed PEW proteins to interact less with each other and form smaller thermal aggregates during thermal denaturation, which facilitated the formation of fine chain gel networks and thus improved the transparency of the gels. The present study initially reveals the molecular basis of the high transparency of PEW thermal gels and provides a theoretical reference for the development of new highly transparent protein materials.

Designing future foods: Harnessing 3D food printing technology to encapsulate bioactive compounds

Bioactive compounds (BCs) provide numerous health benefits by interacting with one or more components of living tissues and systems. However, despite their potential health benefits, most of the BCs have low bioaccessibility and bioavailability, hindering their potential health-promoting activities. The conventional encapsulation techniques are time-consuming and have major limitations in their food applications, including the use of non-food grade chemicals, undesired sensory attributes, and storage stability issues. A cutting-edge, new technique based on 3D printing can assist in resolving the problems associated with conventional encapsulation technologies. 3D food printing can help protect BCs by incorporating them precisely into three-dimensional matrices, which can provide (i) protection during storage, (ii) enhanced bioavailability, and (iii) effective delivery and controlled release of BCs. Recently, various 3D printing techniques and inks have been investigated in order to create delivery systems with different compositions and geometries, as well as diverse release patterns. This review emphasizes the advances in 3D printing-based encapsulation approaches, leading to enhanced delivery systems and customized food formulations.

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.

Protein-polysaccharide-based delivery systems for enhancing the bioavailability of curcumin: A review

In recent years, a wide attention has been paid to curcumin in medicine due to its excellent physiological activities, including anti-inflammatory, antioxidant, antibacterial, and nerve damage repair. However, the low solubility, poor stability, and rapid metabolism of curcumin make its bioavailability low, which affects its development and application. As a unique biopolymer structure, protein-polysaccharide (PRO-POL)-based delivery system has the advantages of low toxicity, biocompatibility, biodegradability, and delayed release. Many scholars have investigated PRO-POL -based delivery systems to improve the bioavailability of curcumin. In this paper, we focus on the interactions between different proteins (e.g. casein, whey protein, soybean protein isolate, pea protein, zein, etc.) and polysaccharides (chitosan, sodium alginate, hyaluronic acid, pectin, etc.) and their effects on complexes diameter, surface charge, encapsulation drive, and release characteristics. The mechanism of the PRO-POL-based delivery system to enhance the bioavailability of curcumin is highlighted. In addition, the application of PRO-POL complexes loaded with curcumin is summarized, aiming to provide a reference for the construction and application of PRO-POL delivery systems.

Structural and textural properties of walnut protein gels induced by ultrasound and transglutaminase: encapsulation and release of tea polyphenols

This study investigated the synergy of ultrasonic and transglutaminase (TGase) treatment on the structural, physicochemical, rheological, gelation properties and controlled release properties of dehulled walnut proteins (DWP). The results showed that after ultrasonic-TGase treatment, the surface hydrophobicity was decreased, indicating the involvement of disulfide bonds in gel formation. Scanning electron microscopy (SEM) showed that ultrasonic-TGase treatment resulted in a more uniform and denser microstructure of DWP gels. Ultrasonic-TGase treatment changed the secondary structure of the DWP gels as determined by Fourier transform infrared spectroscopy, with an increase in α-helix, β-turn and random coils and a decrease in β-sheets. In addition, in vitro drug release profiles showed that ultrasonic-TGase treatment promoted the cross-linking of protein molecules and formed a dense network to embed tea polyphenols (TP), thereby slowing down the digestion of TP in simulated gastric fluid and achieving the purpose of slow-release in simulated intestinal fluid. Thus, the synergy of ultrasonic and TGase treatment might be an effective method to improve gel properties and expand the application of protein gels in the food industries.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05756-6.

Allergenicity, assembly and applications of ovalbumin in egg white: a review

Ovalbumin (OVA), the most abundant protein in egg whites, has been widely used in various industries. Currently, the structure of OVA has been clearly established, and the extraction of high-purified OVA has become feasible. However, the allergenicity of OVA is still a serious problem because it can cause severe allergic reactions and may even be life-threatening. The structure and allergenicity of the OVA can be altered by many processing methods. In this article, a detailed description on the structure and a comprehensive overview on the extraction protocols and the allergenicity of OVA was documented. Additionally, the information on assembly and potential applications of OVA was summarized and discussed in detail. Physical treatment, chemical modification, and microbial processing can be applied to alter the IgE-binding capacity of OVA by changing its structure and linear/sequential epitopes. Furthermore, research indicated that OVA could assemble with itself or other biomolecules into various forms (particles, fibers, gels, and nanosheets), which expanded its application in the food field. OVA also shows excellent application prospects, including food preservation, functional food ingredients and nutrient delivery. Therefore, OVA demonstrates significant investigation value as a food grade ingredient.

Elastic and transparent ovalbumin hydrogels formed via succinylation combined with pH-shifting treatment

Ovalbumin (OVA) is a model protein with extensive research on structure and function, however, the application of OVA in food processing is limited due to its low gelation properties. In this study, thermally-induced highly transparent and elastic hydrogels from OVA pretreated by succinylation combined with pH-shifting method were reported. Transmission electron microscope (TEM) and free sulfhydryl groups determination revealed that the pretreatment induced the stretching of the protein structure and promoted the formation of preliminary aggregates. Further heating the pretreated OVA suspension resulted in a homogeneous and macroporous gel network with thin connecting walls. Such homogeneous gel network structures may be related to the effective modulation of the thermal aggregation efficiency of proteins by succinylation and the high level of protein unfolding by pH-shifting treatments, which synergistically allowed for more active sites to be created during heating to facilitate intermolecular interactions, including hydrogen bonding and hydrophobic interactions. Notably, the method resulted in a 507.14% increase in elasticity, a 60.74% increase in water holding capacity of the OVA hydrogels compared to the native OVA hydrogels without pretreatment. Also, the hydrogels were transparent with 73.11% light transmittance. In conclusion, succinylation and pH-shifting combined treatment could be an effective method for the preparation of OVA hydrogels with superior gelation properties.

Effects of dual succinylation and ultrasonication modification on the structural and functional properties of ovalbumin

In this study, the functional properties of ovalbumin (OVA) were improved through dual modification with succinylation (succinylation degrees of 32.1 % [S1], 74.2 % [S2], and 95.2 % [S3]) and ultrasonication (ultrasonication durations of 5 min [U1], 15 min [U2], and 25 min [U3]), and the changes in protein structures were explored. Results showed that as the succinylation degree was increased, the particle size and surface hydrophobicity of S-OVA decreased by the maximum values of 2.2 and 2.4 times, respectively, causing emulsibility and emulsifying stability to increase by 2.7 and 7.3 times, respectively. After ultrasonic treatment, the particle size of succinylated-ultrasonicated OVA (SU-OVA) had decreased by 3.0-5.1 times relative to that of S-OVA. Moreover, the net negative charge of S3U3-OVA had increased to the maximum value of - 35.6 mV. These changes contributed to the further enhancement in functional indicators. The unfolding of the protein structure and the conformational flexibility of SU-OVA were illustrated and compared with those of S-OVA via protein electrophoresis, circular dichroism spectroscopy, intrinsic fluorescence spectroscopy, and scanning electron microscopy. The dually modified OVA emulsion (S3U3-E) presented small droplets (243.33 nm), reduced viscosity, and weakened gelation behavior that were indicative of even distribution, which was visually proven by confocal laser scanning microscopy images. Furthermore, S3U3-E exhibited favorable stability, a particle size that was almost unchanged, and a low polydispersity index (<0.1) over 21 days of storage at 4 °C. The above results demonstrated that succinylation combined with ultrasonic treatment could be an effective dual modification method for enhancing the functional performance of OVA.

Research advance of non-thermal processing technologies on ovalbumin properties: The gelation, foaming, emulsification, allergenicity, immunoregulation and its delivery system application

Ovalbumin (OVA) is the most abundant protein in egg white, with excellent functional properties (e.g., gelling, foaming, emulsifying properties). Nevertheless, OVA has strong allergenicity, which is usually mediated by specific IgE thus results in gut microbiota dysbiosis and causes atopic dermatitis, asthma, and other inflammation actions. Processing technologies and the interactions with other active ingredients can influence the functional properties and allergic epitopes of OVA. This review focuses on the non-thermal processing technologies effects on the functional properties and allergenicity of OVA. Moreover, the research advance about immunomodulatory mechanisms of OVA-mediated food allergy and the role of gut microbiota in OVA allergy was summarized. Finally, the interactions between OVA and active ingredients (such as polyphenols and polysaccharides) and OVA-based delivery systems construction are summarized. Compared with traditional thermal processing technologies, novel non-thermal processing techniques have less damage to OVA nutritional value, which also improve OVA properties. OVA can interact with various active ingredients by covalent and non-covalent interactions during processing, which can alter the structure or allergic epitopes to affect OVA/active components properties. The interactions can promote OVA-based delivery systems construction, such as emulsions, hydrogels, microencapsulation, nanoparticles to encapsulate bioactive components and monitor freshness for improving foods quality and safety.

Design of glucono-δ-lactone-induced pinto bean protein isolate/κ-carrageenan mixed gels with various microstructures: fabrication, characterization, and release behavior

BACKGROUND

Protein gels are used for different purposes, such as providing good texture, serving as fat replacers, and enhancing the nutritional and functional characteristics of foods. They can also deliver controlled release agents for sensitive drugs. The objective of this study was to investigate the impact of κ-carrageenan (kcr) concentration (0, 1.5, 3, and 4.5 mg g^-1 ) on the morphological and physicochemical properties and release behavior of glucono-δ-lactone (GDL)-induced pinto bean protein aggregate (PBA) gels.

RESULTS

When κ-carrageenan concentration increased from 0 to 1.5 and 3 mg.g^-1 , the firmness of the samples increased significantly, by 2.04 and 3.7 fold, respectively (P < 0.05). A compact and homogenous network with considerable strength and maximum water-holding capacity (97.52 ± 1.17%) was obtained with the addition of 3 mg g^-1 κ-carrageenan to the gel system. Further increasing the κ-carrageenan concentration to 4.5 mg g^-1 produced a coarse gel structure with higher storage modulus (G'), firmness (6.30-fold), thermal stability, and entrapment efficiency (85.6%). Depending on the κ-carrageenan concentration, various microstructures from protein continuous phase to κ-carrageenan continuous phase were observed. The release test indicated that 70.25% of the loaded curcumin was released in the simulated gastrointestinal tract for pure PBA gels. In contrast, for binary gels containing 4.5 mg g^-1 κ-carrageenan, curcumin was protected in the upper gastrointestinal tract, and 64.45% of loaded curcumin was delivered to the colon.

CONCLUSION

Our study showed that κ-carrageenan/PBA gels had high entrapment efficiency and could protect curcumin in the upper gastrointestinal tract. The hydrogels are therefore very valuable for colon-targeting delivery purposes. © 2022 Society of Chemical Industry.

Spectroscopic Characterization of the Binding and Release of Hydrophilic, Hydrophobic and Amphiphilic Molecules from Ovalbumin Supramolecular Hydrogels

Protein-based hydrogels have attracted growing attention for pharmaceutical and biomedical applications. Ovalbumin (OVA), the hen egg white albumin, possessing good foaming and gelling properties and being widely used in the food industry, has recently been indicated as a potential pharmaceutical vehicle. In this study, the binding and release properties of pure OVA hydrogels were investigated by electron paramagnetic resonance (EPR) spin labeling. The comparative analysis between OVA and serum albumin (SA) hydrogels revealed the same release kinetics of hydrophilic 3-carbamoyl-proxyl and 3-carboxy-proxyl, suggesting the diffusion-dominated release of small probes from both hydrogel types. The results obtained with the amphiphilic 16-doxylstearate (16-DS) indicate that OVA, unlike SAs, does not possess a specific fatty acid binding site. However, the OVA hydrogels were able to accommodate a two-fold excess of 16-DS, resulting from protein thermally induced conformational changes, as confirmed by Raman spectroscopy. Similarly, the hydrophobic modified paullone ligand HL, which was initially free in the OVA solution, was bound in the hydrogel. The hydrogels were found to retain a significant amount of 16-DS and HL after 7-day dialysis in physiological saline. The observed facilitated binding of amphiphilic/hydrophobic molecules in OVA hydrogels compared to the solution, and their sustained release, demonstrate the applicability of OVA hydrogels in pharmaceutics.

Encapsulation and sustained release of curcumin by hawthorn pectin and Tenebrio Molitor protein composite hydrogel

In this study, the effects of pH value, mixing ratio and the Ca²⁺ concentration on the complex gelation of hawthorn pectin (HP) and Tenebrio Molitor protein (TMP) were investigated. The turbidity results showed that the composite gel had the maximum polymer concentration when the mixing ratio was 2:1 and the pH value was 3.35. The rheological measurement results showed that TMP/HP (15 mmol/L) hydrogel (THIH) had the highest storage modulus and loss modulus, indicating that the properties of the hydrogel at this Ca²⁺ concentration had been significantly improved. The results of scanning electron microscope and pore size also proved that the network structure prepared under this condition was compact and uniform, the pore size was small, which was beneficial to the entrapment of active components. Subsequently, in order to explore the storage stability and antioxidant activity of THIH-loaded curcumin in simulated gastrointestinal environment, in vitro simulated digestion experiment was carried out and satisfactory results were obtained. To sum up, THIH was a promising delivery system with broad application prospects, which was expected to provide a novel idea for the entrapment and delivery of active components.

Egg white protein-based delivery system for bioactive substances: a review

Some bioactive substances in food have problems such as poor solubility, unstable chemical properties and low bioavailability, which limits their application in functional food. Recently, many egg white protein-based delivery carriers have been developed to improve the chemical stability, biological activity and bioavailability of bioactive substances. This article reviewed the structure and properties of several major egg white proteins commonly used to construct bioactive substance delivery systems. Several common carrier types based on egg white proteins, including hydrogels, emulsions, micro/nanoparticles, aerogels and electrospinning were then introduced. The biological functions of common bioactive substances, the limitations, and the role of egg white protein-based delivery systems were also discussed. At present, whole egg white protein, ovalbumin and lysozyme are most widely used in delivery systems, while ovotransferrin, ovomucoid and ovomucin are less developed and applied. Egg white protein-based nanoparticles are currently the most commonly used delivery carriers. Egg white protein-based hydrogels, emulsions, and microparticles are also widely used. Future research on the application of various egg white proteins in developed new delivery systems will provide more choices for the delivery of various bioactive substances.

Formation mechanism of high-viscosity gelatinous egg white among "Fenghuang Egg": Phenomenon, structure, and substance composition

"Fenghuang Egg" is a special egg product incubated for 12 days by fertilized hen eggs. Its egg white contains high-viscosity and excellent thermal gel strength. A comparative study on the differences in gel properties, structure, and substance composition between fresh egg white (FEW) and "Fenghuang egg" gelatinous egg white (GEW) was carried out. Experimental results showed GEW had better apparent viscosity, as well as the hardness, cohesiveness and water holding capacity (WHC) of thermal gel; the content and size of aggregate structure increased significantly in GEW, and a fibrous dense network composed of numerous spherical nanoparticles connected in series was formed after heating. In addition, it also discovered that more water molecules in GEW existed in the form of bound water. A total of 41 proteins changed significantly in FEW and GEW, Mucin 6 might be the main reason for the enhanced viscosity of GEW, and OVA might be the dominant protein differentiating the thermal gel properties between FEW and GEW. This study revealed that the differences in gel properties and structures between FEW and GEW were closely related to the content of highly glycosylated globular proteins, laying a theoretical foundation for the application of high-viscosity egg whites.

Modification methods and applications of egg protein gel properties: A review

Egg protein (EP) has a variety of functional properties, such as gelling, foaming, and emulsifying. The gel characteristics provide a foundation for applications in the food industry and research on EP. The proteins denature and aggregate to form a dense three-dimensional gel network structure, with a process influenced by protein concentration, pH, ion type, and strength. In addition, the gelation properties of EP can be altered to varying degrees by applying different treatment conditions to EP. Currently, modification methods for proteins include physical modification (heat-induced denaturation, freeze-thaw modification, high-pressure modification, and ultrasonic modification), chemical modification (glycosylation modification, phosphorylation modification, acylation modification, ethanol modification, polyphenol modification), and biological modification (enzyme modification). Pidan, salted eggs, egg tofu, and other egg products have unique sensory properties, due to the gel properties of EP. In accessions, EP has also been used as a new ingredient in food packaging and biopharmaceuticals due to its gel properties. This review will further promote EP gel research and provide guidance for its full application in many fields.