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Background: Salted hen egg yolks are less oily and less flavorful than salted duck egg yolks. However, hen eggs have a more adequate market supply and have a broader application prospect than duck eggs. In the present study, egg yolks, plasma, and granules were dehydrated by adding 1% NaCl to simulate traditional curing process of salted egg yolk. The changes in the pickling process of hen egg yolks (HEY) and duck egg yolks (DEY) plasma and granules were compared to reveal the gelation mechanism and the underlying causes of quality differences in salted HEY and DEY. Salted HEY can be compared with the changes in DEY during the pickling process to provide a theoretical basis for the quality improvement of salted HEY to salted DEY., Results: The results showed that both plasma and granules were involved in gel formation, but exhibited different aggregation behaviors. Based on the intermolecular forces, the HEY proteins achieved aggregation mainly through hydrophobic interactions and DEY proteins mainly through covalent binding. According to spin-spin relaxation time, HEY gels immobilized a large amount of lipid and interacted strongly with lipids. DEY gels showed much free lipid and had weak interaction with lipid. The microstructure showed that HEY proteins were easily unfolded to form a homogeneous three-dimensional gel network structure after salting, whereas heterogeneous aggregates were formed to hinder the gel development in DEY. Changes in protein secondary structure content showed that pickling can promote the transformation of the α-helices to β-sheets structure in HEY gels, whereas more α-helices structure was formed in DEY gels., Conclusion: The present study has demonstrated that different gelation behaviors of hen and duck egg yolk proteins (especially in plasma) through salting treatment led to the difference in the quality of salted HEY and DEY. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

In this study, the oxidation of egg yolk lipids (EYL) by salt-induced heat and non-heat treatments was investigated for quality and flavor. The correlation between physicochemical properties, lipid oxidation and antioxidant activity was modeled using partial least squares discriminant analysis (PLS-DA). The results indicated that the prolonged salt-induced synergistic heat treatment produced the highest level of lipid oxidation, antioxidant activity and oil exudation, along with the lowest level of polyunsaturated fatty acid content. In addition, higher contents of pyrazines and fewer acid species were detected, which was not the case with the salt-free heat treatment. In total, 14 identical volatile organic compounds (VOCs) were produced, yet their overall flavor profiles determined by the electronic nose would remain dramatically distinguished. Therefore, heat treatment was particularly critical for lipid oxidation and the generation of aromatic compounds, implying that heat-treated EYL induced by salt is a flavor component with good antioxidant potential., 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. Published by Elsevier Ltd.)

The aim of this study was to investigate effects of cholesterol removal treatment (CRT) on the flavor, taste, texture, color, and nutritional value of hot gel egg yolk (EY). The off-odor, volatile components and taste of EY treated with CRT were studied by electronic nose (E-nose), gas chromatography-mass spectrometry (GC-MS) and electronic tongue (E-tongue). The effect of CRT on the nutritional value of EY was studied by amino acid and fatty acid analysis. The CRT significantly reduced the content of hexanal, 2-amyl-furan, 1-octene-3-ol, styrene and heptanal in EY1-EY4, also decreased its bitter taste without affecting other taste and elasticity. In addition, the CRT did not affect the essential amino acids (EAA) content and L*, a* and b* values of EY1-EY4, but it led to the reduction in polyunsaturated fatty acids (PUFA) content. In general, the CRT is an effective way to reduce the off-odor of EY without affecting consumer acceptance., 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 © 2023. Published by Elsevier Ltd.)

Salted egg yolks (SEY) have a desirable and unique flavor with multiple underlying applications in food processing, and their abundant lipids contribute to a creamy and pleasant aroma. However, it is important to maintain the stability of the SEY flavor, which depends to a large extent on the egg species and the processing method. This study aimed to extract different SEY lipids with conventional solvents, analyze the fatty acid composition, and screen the volatile compounds to elucidate the flavor differences between salted hen eggs and duck eggs. Compared to ethanol extraction, acetone-extracted lipids had lower acid value and viscosity, and almost had no phospholipid content. Fatty acid analysis revealed that the highest content of fatty acid in SEY lipids was oleic acid, followed by palmitic acid and linoleic acid, while there were significant variations of different SEY lipids in the fatty acid profiles. The volatile compounds were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and the overall odor was detected by the electronic nose (E-nose). A total of 27 volatile compounds were analyzed in SEY lipids and divided into 8 chemical classes. The aldehydes, furans and pyrazines were decreased, and the hydrocarbons were increased compared with untreated SEY. The combination of the physical properties and flavor evaluation of SEY lipids could provide a theoretical basis for the extension of the characteristic flavor matrix in SEY., 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 © 2022. Published by Elsevier Ltd.)

In this study, the effect of freeze-thaw treatment on isolation of IgY was investigated, with macrograph, protein concentration, solid content, and transmittance evaluated. The results showed that higher refrigeration power (at -18 °C for more than 4 h and -40 °C for more than 2 h) caused yolk gelation and was helpful for removing heteroproteins. To reveal the mechanism of freeze-induced gelation assisting isolation of IgY, the properties of yolk frozen at -5°C, -18 °C and -40 °C for 8 h were determined, with SDS-PAGE, rheology property, low field NMR and interactions between proteins evaluated. As the results showed, the purity of separated IgY increased obviously (frozen at -18 °C and -40 °C), corresponding to the removal of LDL which aggregated during freezing. LDL aggregation may be triggered by hydrophobic interaction during boundary water crystallization. Therefore, freeze-induced yolk gelation is beneficial for IgY isolation by keeping LDL in dense gel structure while releasing IgY to the supernatant., (Copyright © 2021. Published by Elsevier Ltd.)

Background: Egg yolk, as a natural emulsifier, is widely used in high-oil-phase food systems, such as mayonnaise and salad. However, the application of egg yolk in an oil-in-water system is still limited due to poor emulsifying stability. To improve the emulsifying capacity of egg yolk, the effect of chitosan addition sequence and concentration on emulsifying properties (creaming stability, thermal tolerance and oxidation resistance) of egg yolk hydrolysates were investigated., Results: Stacking sequence of multilayer materials has an influence on properties of composite emulsions. The composite emulsions with egg yolk hydrolysis dominate at the interface (functioning on reducing interfacial tension), and chitosan layered on the surface (providing steric hindrance) displayed better stability. Little chitosan addition (0.5 g × kg -1 , w/w) was unhelpful for the dispersion of emulsion droplets as a result of bridging flocculation. At a chitosan concentration of 2 g kg -1 (w/w), the composite emulsion possesses the best stability. When chitosan concentration was higher than 2 g kg -1 (w/w), depletion flocculation would occur. Hydrolyzed egg yolk prepared composite emulsions possessed better thermal resistance, but with poorer oxidative stability as compared to natural egg yolk. In combination with chitosan it also displayed a negative effect on the oxidative stability of the emulsion system., Conclusion: The research revealed the effect of chitosan addition on the physical and chemical stability of emulsions prepared with egg yolk hydrolysates. The results could provide guidance on expanding the application of egg yolk as an emulsifier in water-abundant food systems such as beverages. © 2021 Society of Chemical Industry., (© 2021 Society of Chemical Industry.)

This study reported a powder formulation containing omega-3-rich algal oil emulsions stabilized by egg yolk granules (EYGs)/lecithin composites. The improved physical stability of the algal oil samples due to increasing pH and lecithin addition was beneficial to the oxidative stability through analysis of free radical scavenging activities, metal ion chelating activities, and the release of primary and secondary oxidation products during accelerated storage (12 days, 60 °C). In addition, the effect of three antioxidants, i.e. ascorbic acid (VC), ascorbyl palmitate (AP), and α-tocopherol (VE), on lipid oxidation was investigated. Results showed that antioxidant partitioning at different regions of the emulsion system influenced its ability to prevent oxidation with the effectiveness of AP (at the O/W interface) > VE (in the oil phase) > VC (in the aqueous phase). This study developed a new powder-based emulsion formulation for algal oils with superior oxidative stability as an alternative source of omega-3., (Copyright © 2020. Published by Elsevier Ltd.)

The salted egg yolk (SEY) is very popular in China for its pleasant flavor and texture. However, the long production cycle of traditional pickling and the waste of salted egg white had limited its industrialization. To solve these problems, a salted egg yolk flavoring was generated through enzymatic hydrolysis and microwave irradiation from fresh egg yolk in this study. The combination of enzymatic hydrolysis and microwave irradiation could force water and lipids in egg yolk to migrate out, and lead to lipid oxidation in high temperature. Lipid oxidation and Strecker degradation were defined as the major pathways of flavor generation. Among the generated volatile compounds, Hexanal, Heptanal, Benzaldehyde and 2-Pentyl-furan were supposed closely related to SEY flavor. This method could be used as an alternative method for the production of salted egg yolk. Furthermore, it could provide a foundation for further investigation of egg yolk containing flavor system., 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 © 2020. Published by Elsevier Ltd.)

The aim of the present paper was to fabricate egg yolk-modified starch complex at neutral pH as novel emulsifiers to stabilize high internal phase emulsions (HIPEs). Octenyl succinic anhydride (OSA) and hydroxypropyl distarch phosphate (HPDSP) were selected as representative models of surface active and non-surface active polysaccharides. Results of particle diameter, zeta-potential and turbidity indicated that egg yolk-modified starch complex could be formed via electrostatic and hydrophobic interaction. The soluble complex could be formed in egg yolk-OSA starch solutions, which was beneficial to decrease the droplet size and increase the apparent viscosity of HIPEs. However, at the high concentration of HPDSP (3-4 %), the insoluble complex could be formed in egg yolk-HPDSP solutions, which increased the viscosity of water phase and promoted the stability of oil droplets. This work provides a feasible way to successfully fabricate HIPE, which may help to expand their application in the food industry., (Copyright © 2020. Published by Elsevier Ltd.)

In this study, the influence of NaCl on the flocculation behavior and gel properties of egg yolk/κ-carrageenan mixed dispersions or emulsions were studied. As a result of NaCl incorporation, there was a decrease in the mean droplet size, zeta potential, degree of flocculation and viscosity of the mixed dispersions/emulsions, and the onset point of gelation was also brought forward. Increasing the concentration of NaCl led to a significant increase in gel strength and decrease in gel cohesiveness. Results from low field nuclear magnetic resonance (LF-NMR) confirmed that the addition of NaCl could significantly reduce the hydration ability of gel molecules and increase the content of immobilized water of hydrogels as the gel strength increased, while the water holding capacity of emulsion gels was depressed with the incorporation of oil. These findings suggested the flocculation state and gel properties of egg yolk/κ-carrageenan mixed dispersions/emulsions can be tailored by adjusting NaCl for food formulations., 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 © 2020. Published by Elsevier Ltd.)

Summary: The rapid shell‐less curing method significantly simplifies the processing cycle of salted egg yolks (SEYs). However, differences in flavour attributes between rapidly cured SEYs and traditionally cured SEYs have yet to be clearly established. Herein, a comprehensive evaluation of the volatile compounds in SEYs using HS‐SPME‐GC‐MS and HS‐GC‐IMS aims to delineate the flavour characteristics under varying preparation methods. Despite reduced oil exudation, the rapid salting process resulted in higher levels of free amino acids than the traditional approach. Hexanal, nonanal, 1‐octen‐3‐ol, 2‐pentyl‐furan, phenylacetaldehyde, benzaldehyde, 2‐octenal, and 2,5‐dimethyl‐pyrazine were identified as significant contributors to the SEY flavour profile. Conversely, salted hen egg yolks contained methional, decanal and 2‐methyl‐pyrimidine; whereas salted duck egg yolks presented with (E,E)‐2,4‐decadienal, 2,6‐diethyl‐pyrazine and nonanoic acid. Principal component analysis of the E‐nose revealed that the aroma profile of rapid curing (SHY‐R25) was more similar to that of traditional curing (SHY). The rapid preparation technology presented a viable alternative to traditional pickling, capable of partially replicating the flavour of traditional salted egg yolks within a single day. These findings contributed to a more scientific application and preparation of SEY flavouring bases, providing a theoretical basis for flavour enhancement and development. [ABSTRACT FROM AUTHOR]

In this study, the flavor characteristics and physicochemical properties of salted egg yolk (SEY) under different cooking methods (steaming/baking/microwaving) were investigated. The microwave-treated SEY exhibited the highest levels of salt content, cooking loss, lightness, and b* value, as well as the highest content of flavor amino acids. A total of 31, 27, and 29 volatile compounds were detected after steaming, baking, and microwave treatments, respectively, covering 10 chemical families. The partial least squares discriminant analysis confirmed that 21 compounds, including octanol, pyrazine, 2-pentyl-furan, and 1-octen-3-ol, were the key volatile compounds affecting the classification of SEY aroma. The electronic nose revealed a sharp distinction in the overall flavor profile of SEY with varying heat treatments. However, no dramatic differences were observed in terms of fatty acid composition. Microwave treatment was identified as presenting a promising approach for enhancing the aroma profile of SEY. These findings contribute novel insights into flavor evaluation and the development of egg products as ingredients for thermal processing. [ABSTRACT FROM AUTHOR]

BACKGROUND: Egg yolk granules (EYGs)‐soy lecithin (SL) complex is a newly developed delivery system that is effective for improving the storage stability of hydrophobic bioactive compounds. However, the formation mechanism of EYGs and SL complex and its effect on the gastrointestinal fate of lutein‐loaded emulsions needs to be investigated further. RESULTS: Adding SL greatly improved the surface activity of the EYGs, as evidenced by reduced surface tension and an increased adsorption rate to the oil/water interface. Hydrophobic interaction was the dominant force in the formation of EYG‐SL complex, with hydrogen and ionic bonds playing complementary roles. Using the EYG‐SL complex, stable oil‐in‐water emulsions were formed and exhibited an enhanced retention ratio and bioaccessibility of lutein after simulated digestion. Correlation analysis demonstrated that the additional anti‐oxidant activity as a result of EYGs was responsible for the high retention of lutein, whereas low surface tension facilitated the micellization of bioaccessible lutein. CONCLUSION: The present study shows that the EYG and SL have a synergistic effect with respect to improving the retention ratio and bioaccessibility of lutein in emulsions stabilized by EYG‐SL complex after digestion and this will guide the development of value‐added oil‐in‐water emulsion products using protein‐lecithin complex as a promising nutrient delivery vehicle. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Spray dried egg yolk powder (EYP) is a kind of food ingredient with high nutritional value. However, its low solubility and insufficient emulsifying properties restrict its applications in the food industry. In this study, a new method of dual enzymatic hydrolysis (phospholipase and protease) was proposed to improve the functional properties of EYP including emulsifying properties, solubility, rehydration time and so on. The optimal conditions were determined to be 50 U/g (phospholipase A1 (PLA1)) and 250 U/g (neutral protease). Under these optimal conditions, the solubility of HYP (hydrolyzed EYP) treated by dual enzyme (61.30%) was significantly higher than that of unhydrolyzed EYP (16.49%) or HYP treated by single PLA1 (23.97%). Meanwhile, the emulsifying stability index (ESI) of HYP (hydrolyzed EYP) treated by dual enzymes was about 16/1.4 times larger than unmodified EYP/single PLA1 modified HYP. The increasing electronegativity and decreasing surface hydrophobicity/surface tension of HYP could be responsible for the above results. Scanning electron microscopy (SEM) revealed that dual-enzyme hydrolysis could promote the formation of fine HYP with pore structure, enabling it to rehydrate more effectively. In addition, the usage of protease could improve the radical scavenging activity of dual enzyme modified HYP by releasing antioxidant peptides. This study could provide new insights to promote the techno-functionality of EYP, thus optimizing its utilization as a high-performance emulsifier in the food industry. [Display omitted] • A dual-enzyme method was developed to modify the properties of egg yolk powder. • Strong synergy between phospholipase and protease was found. • SDS-PAGE and FTIR were used to reveal structural changes in proteins and lipids. • The relationship between physicochemical and functional properties was analyzed. [ABSTRACT FROM AUTHOR]

In this study, the differences in the gelation, digestibility and release of antioxidant peptides of egg white (EW)/yolk (EY) in boiled eggs prepared by different boiling times were investigated. The hardness, gumminess and chewiness of boiled EW/EY both showed an increase trend with the duration of boiling time. Prolonging the boiling time increased the proportion of immobilized water in boiled EW, but reduced the retention ability of boiled EY for water or lipid. Increasing boiling time increased the content of β-sheet of boiled EW/EY at the expense of α-helix with varying degrees, accompanying with the increase of the disulfide bond and the formation of dense gel network structure. The results of in-vitro simulated digestion showed that boiled EW, especially prepared by boiling for a longer time, had a lower protein digestibility and less release of antioxidant peptides than that of boiled EY due to its compact gel network and large broken particles after digestion. This work demonstrated that prolonged boiling time will improve the gel strength of boiled EW and boiled EY, but is not conducive to their digestion and the release of antioxidant peptides. [Display omitted] • Differences in gelation and digestibility of cooked egg white/yolk were evaluated. • Long boiling time increased the water holding of egg white, but not for egg yolk. • Short boiling time improved the digestibility of boiled eggs. • The digestibility of cooked egg white differed from yolk due to their broken degree. [ABSTRACT FROM AUTHOR]

The effects of pH and NaCl on the physicochemical (zeta potential, particle size and surface tension) and interfacial properties (foaming and emulsifying properties) of egg white and yolk were investigated in order to protmote its applications in food industries. Results showed that the increase of foam expansion power/emulsifying activity index of egg white exhibited a good correlation with the decrease of particle size and increase of surface tension. However, the extra charge and decreasing surface tension of egg white/yolk dispersions at pH > 7.0/NaCl ≥ 0.6% resulted in the destabilization of foams. The emulsifying stability of egg yolk dispersions continued climbing to pH 10.0 due to the continuous reduction of particle size and started declining with the slow decrease amplitude of particle size at NaCl > 1.8%, thus z-average particle size is the main factor that dominates the emulsifying stability index of egg yolk dispersions. These results indicated that the foaming/emulsifying properties of egg white/yolk proteins can be manipulated by altering the physicochemical characteristics such as charge, surface tension and particle size in order to achieve optimal functional properties for food industrial applications. [ABSTRACT FROM AUTHOR]

Hypocrellins, including hypocrellin A and hypocrellin B, are natural red pigments isolated from a traditional Chinese medicine. The present work was designed to investigate the influence of dietary HA supplementations on the colour and emulsifying properties of egg yolk and HA distributions in tissues of laying hens. A Chinese hen breed (black-bone silky fowl) was used. Ninety-six layers were assigned randomly to diets containing 0, 10, 30 and 50 mg HA per kilogram for 21 days. HA concentrations in egg yolk and tissues of laying hens such as ovary, liver, lung, heart, gizzard and breast muscle were determined by HPLC. Dietary HA supplementations improved the colour of egg yolk ( P < 0.05), whereas no significant differences ( P > 0.05) in the emulsifying properties of egg yolk were observed. There was a dose-dependent manner increase in egg yolk HA content in response to dietary HA supplementations ( P < 0.05). The highest HA concentration was measured in ovary followed by liver and egg yolk. [ABSTRACT FROM AUTHOR]

The egg yolk powder (EYP) was modified in this study by incorporating the tea polyphenols (TP), rosemary extract (RE), curcumin (CC), ascorbic acid (AA), and vitamin E (VE) to create the complex of polyphenols/vitamins-EYP. The structure, flavor, and emulsification properties of the complex were investigated. The results demonstrated that the addition of these five substances enhanced the flavor of EYP. Among them, VEP (EYP modified by VE) exhibited the flavor profile closest to EYP, while TPP (EYP modified by TP) had the most different flavor compared to EYP. This was because VE could induce secondary and tertiary structural changes in EYP and exposed more functional groups for binding with volatile flavor compounds such as hexanal, 1-octen-3-ol, and benzaldehyde, thereby improving the overall flavor of EYP. However, due to its larger molecular weight (1099.62 Da), VE exhibited the limited degree of interaction with EYP, thereby enabling it to preserve the overall flavor profile of EYP. On the other hand, TP possessed most active hydroxyl groups, which easily interacted with EYP, forming new complexes that significantly altered its flavor characteristics. Among the five modified powders, VEP had the highest emulsification, but it was still lower than that of EYP. This was because the particle size of VEP (1592.75 nm) was higher than that of EYP (821.88 nm), which was not conducive to the rapid movement to the oil-water interface, resulting in the reduced emulsification. [Display omitted] • Flavor substances are bound to proteins through non-covalent interactions such as hydrophobic interactions. • The molecular weight of VE is higher, making it less prone to interact with EYP and exerts the least impact on its flavor. • TP, with the most active hydroxyl groups, leads to a significant alteration in the flavor profile of EYP. • The combination of polyphenols/vitamins with EYP increases the particle size and reduces the emulsification. [ABSTRACT FROM AUTHOR]

The effects of three different enzyme treatments on the structure and volatile compounds of egg yolk protein were investigated. The secondary and tertiary structures, as well as volatiles, were characterized using ultraviolet spectroscopy (UV), fourier transform infrared (FTIR) spectroscopy, free sulfhydryl group analysis, and gas chromatography-mass spectrometry (GC-MS). FTIR analysis revealed a decrease in the contents of intermolecular, intramolecular, and intermolecular antiparallel β-sheets while an increase in random coils was observed. The contents of α-helices and β-turns did not show significant changes, indicating a reduction in protein compactness. Enzymatic treatment led to an increase in hydrophobic interaction, electrostatic interaction, and hydrogen bond formation within the egg yolk hot gel (EYG). Structural characterization demonstrated that EYG formed large uniform air chamber cavities after lipase hydrolysis (LEYG), while EYG hydrolyzed by papain (PEYG) and by flavor protease (FEYG) exhibited more compact structures. In addition, the binding of proteins to flavor substances inhibited the release of volatile flavor compounds. These findings provide insights into enhancing the flavor and texture of egg yolk by modulating its protein structure. [Display omitted] • The enzyme treatment induced a significant alteration in the secondary structure, resulting in increased flexibility. • The flavor components potentially formed hydrophobic interactions with egg yolk, thereby improving their flavor profile. • The alteration of free sulfhydryl group could potentially result in a reduction in gel strength. • The interrelation among protein structure, gel texture, and flavor was investigated through diverse analytical approaches. [ABSTRACT FROM AUTHOR]

Hen egg yolk (EY) has a variety of techno-functionalities, including emulsifying, gelling, and film-forming properties. However, the application of native EY and its fractions is still limited due to the insufficient functionalities. Thus, various modification treatments have been used to improve the functionalities. In addition, there has been increasing research interest to explore the potential of modified EY and its fractions for applications in developing value-added food products. This review provides a brief introduction of EY structures, fractions, and components and focuses on discussing a wide range of existing modification methods and the mechanism of each method to change the structure and improve the desirable functionality of EY and its fractions. Three emerging applications of EY in food formulation industry, i.e. nutrient encapsulation and delivery system, unmodified EY substitutes, and edible films, are finally highlighted. Recent studies have shown that pre-treatment of EY and its fractions are often needed using enzymatic hydrolysis, complexing with polysaccharides, or other chemical, physical, and fermentation methods. The purpose of the pre-treatment is to dissociate the aggregated EY protein state, modify solution characteristics (such as solubility, hydrophobicity, and surface charge), so that the functionality is greatly improved, leading to more stable emulsion systems or other novel EY-based food products. By reviewing the new modification technology and application trends of EY, this review provides expert opinions of future research directions for the development of value-added EY derived food products. • Modification techniques for the functional enhancement of egg yolk are summarized. • Egg yolk derived emulsions or micro-capsules are attractive delivery systems. • Low cholesterol egg yolk fractions are new alternatives for unmodified egg yolk. • Egg yolk components are important candidates in the preparation of edible films. [ABSTRACT FROM AUTHOR]

Abstract The foaming characteristics (foam ability, foam stability and foam microstructure) of fresh foams based on egg white protein, and with the addition of different proportions of egg yolk and yolk fractions (plasma and granules) were analyzed in this research. The relationships between foaming properties and addition of yolk fractions were carried out via surface tension, surface hydrophobicity, apparent viscosity and zeta potential. The results showed that charge properties of yolk fraction dispersions were considered to have positive correlations with their foam stability to egg white. The foam abilities might possibly be determined by their particular structure and interactions with egg white protein. Besides, their interactions could also be represented by surface tension and surface hydrophobicity. Therefore, this study provides a new insight for determining the relationship between foaming properties of egg white contaminated by proportions of egg yolk fractions and the physicochemical properties of egg white/yolk or yolk fractions dispersions. Graphical abstract Image 1 Highlights • Foaming properties of egg white-yolk/fractions were studied. • Components and Structures in yolk/fractions influenced foaming characterization. • Surface indexes dominated foam properties of egg white-yolk/fractions dispersions. • Surface charge resulted in high foam stability of egg white/granules bubbles. [ABSTRACT FROM AUTHOR]

Abstract Egg gel is the combined gelation of egg white (EW) and egg yolk (EY); its properties depend on the fixed ratio of EW and EY in shell egg. This study investigated the gelation properties of egg mixtures in artificial blends to explore innovative egg solutions catering to the market demands and provide guidance for the production of creative egg products. Results showed that solubility of samples decreased with the increase of EY proportion while solid content increased. More surface hydrophobicity and total SH group increases were observed with higher EY proportion. Rheological tests suggested that adding EY decreased samples' initial G' values. Egg gel containing 20% EY presented the largest hardness value, which seems to be related to the fine gel network microstructure. Besides, the springiness and water-holding capacity of gels gradually increased with EY addition, which may be the result of dense microstructure and high solid content of EY. Highlights • Gelling properties of egg white and yolk were dependent on the proteins. • Water-holding capacity of egg gels was closely related to gels' microstructure. • Yolk filled the cavities existing in egg white gels, making microstructure denser. [ABSTRACT FROM AUTHOR]

The effects of NaCl addition on the gelling and water holding properties of egg white/yolk gels were studied via solubility, surface hydrophobicity, reduced sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared spectra (FTIR), textural analysis, low-field nuclear magnetic resonance (LF-NMR) and centrifugation. Results showed that more solubility and surface hydrophobicity increase of egg yolk dispersions were observed than that of egg white dispersions. SDS-PAGE results indicated that the different change trend of surface hydrophobicity between two egg proteins was closely related with the dissociation of egg yolk granule proteins. NaCl-induced protein heat denaturation will result in the decrease of ordered secondary structure (α-helix and β-sheet) by breaking hydrogen bond for both egg protein gels. A rapid decrease ( p < 0.05) in fracture strength/strain of egg white gels was found as the NaCl increased, while the fracture strength/strain of egg yolk gels first rose and then descended, indicating that the significant increases of solubility and hydrophobicity of egg yolk dispersions at a certain NaCl concentration (≤1.8%) were benefit to the formation of strong molecule interaction among gel network. Results from LF-NMR and centrifugation water holding capacity (WHC) tests revealed that NaCl addition affected the WHC of egg white gels by increasing the mobility and distribution of free water, and had a complex influence on proton mobility and relaxation peak changeability of egg yolk gels due to the interaction among lipid, protein and water. [ABSTRACT FROM AUTHOR]

Egg yolk will undergo gelation when it is stored below −6 °C due to protein denaturation and aggregation. In this study, the cryoprotective effects of sugar alcohols with various molecular weights (erythritol, xylitol, mannitol and maltitol) on egg yolks stored at −18 °C were compared, and the corresponding mechanism was elucidated. The rheological and textural properties showed that small molecular weight sugar alcohol could greatly increase the fluidity of frozen-thawed yolk and weaken the gel strength. Smaller molecule sugar alcohol, such as erythritol, had better efficiency in inhibiting the aggregation of proteins during freezing, due to the restricted growth of ice crystals, which was verified by the decrease in the loss of immobile water and crystallization enthalpy. In addition, the dominant interaction between protein molecules changed from hydrophobic interactions to electrostatic interactions in the presence of erythritol. It could be concluded that, small molecule sugar alcohols especially erythritol could more effectively protect proteins from aggregation by inhibiting the denaturation caused by ice crystal growth and hindering intermolecular hydrophobic interactions. • Small molecule sugar alcohol can effectively improve fluidity of frozen egg yolk. • The improved fluidity of frozen egg yolk was related to the reduced aggregation and ice crystal formation. • Erythritol addition could restrict inter-molecular hydrophobic interaction between frozen egg yolk proteins. • The gelation and emulsifying properties of frozen egg yolk were significantly improved. [ABSTRACT FROM AUTHOR]

This study investigated the effects of subcritical fluid extraction on lipid removal and the physicochemical properties of egg yolk powder. In addition, two-step enzymatic hydrolysis was used to improve the physicochemical properties. The content of total lipids and cholesterol decreased to 30.2% and 10.5 mg/g after subcritical propane-butane extraction, respectively, while phospholipids were retained. Protein solubility, surface hydrophobicity and total sulfhydryl results showed that this partial defatting avoided further quality deterioration of egg yolk powder. Scanning electron microscopy and confocal microscopy showed that the surface morphology and distribution of proteins and lipids changed with defatting degree. After two-step enzymatic hydrolysis, protein solubility of subcritical propane-butane extraction egg yolk powder significantly increased to 31.4% and soluble peptides with an average molecular weight lower than 1000 Da accounted for 70.0%. The improved defatted egg yolk powder is rich in protein, peptides and phospholipids and has great potential as a nutritional supplement. [Display omitted] • Subcritical extraction selectively removed triglycerides and cholesterol in yolk. • Phospholipids were retained after subcritical propane and butane extraction. • Part defatting avoided further quality deterioration of defatted egg yolk powder. • Surface morphology and components distribution changed with defatting degree. • Two steps enzymatic hydrolysis improved quality of defatted egg yolk powder. [ABSTRACT FROM AUTHOR]

Abstract: Monodispersed and functional immobilized metal affinity magnetic chondroitin sodium sulfate nanoparticles (short as IMAN @ Fe (III)) were prepared and employed in extracting of Phosvitin Phosphopeptides (short as PPPs) from egg yolk. It was found that the diameter of the magnetic CS nanoparticles was about 20nm, and they could easily be aggregated by a magnet when suspending in the aqueous solution. The adsorption equilibrium of PPPs onto the obtained nanocarriers fitted well with the Langmuir model. The adsorption capacity of PPPs onto the superparamagnetic nanoparticles was influenced by pH and the initial concentration of the peptides solution. The final nitrogen/phosphorus molar ratios (short as N/P) of PPPs from crude egg yolk peptides and phosvitin peptides were low to 5.78 and 5.23, respectively. Compared with traditional methods, the need for preparation of phosvitin before purification is obviated and the higher purity of PPPs were obtained. In conclusion, this type of IMAN @ Fe (III) would bring advantages to the conventional separation techniques of PPPs from chicken egg yolk. [Copyright &y& Elsevier]

Abstracts: The effects of non-treated and modified dried egg yolk on the rheological properties of flour dough were investigated. It indicated that farinograph dough development time, dough stability, and farinograph quality number of the dough increased with the incorporation of the dried egg yolk, while the dough softness decreased. The incorporation of PLA2-treated dried egg yolk into flour has more significant effect on farinograph than that of the non-treated dried egg yolk. Extensograph resistance to extension, and area below the curve (energy) significantly increased with the addition of dried egg yolk, while extensibility decreased and the water adsorption was unchanged. The addition of dried egg yolk lead to the increase of G'' (the storage modulus) and G” (loss modulus) under frequency sweep from 0.1 to 20Hz at 1.5% strain and temperature sweep from 20 to 90°C at 1Hz. The microstructure of the dough showed great difference when non-treated or PLA2-treated dried egg yolk was incorporated into wheat dough. Starch granules flowed into the continuous matrix compared to the blank wheat dough. The gluten network structure of the dough was increased when PLA2-treated dried egg yolk was added. [Copyright &y& Elsevier]

The aim of this study was to describe the foaming properties of egg white protein systems in the presence of egg yolk in varying percentages (0–1, wt%) from an industrial "contamination" view, and to investigate the relationship among their dispersions, batters and cakes in detail. Foaming properties of dispersions, likely the most vital factors determining the quality of final products, were highly correlated with the specific density of batters and specific volume of cakes. To better understand the problem, their effects on interfacial (apparent viscosity, surface tension, size and zeta potential) and structural (optical micrographs, mean bubble sizes and cake slices) properties were also investigated. Results revealed that the interfacial properties of sample dispersions exhibited high correlations with their foaming and structural properties. Rheological characteristics of batters showed higher G′ could be reached during heating with less egg yolk (<0.2, wt%), whereas higher concentrations of egg yolk (0.5–1, wt%) had negative effect on overrun, specific volume and cross-sections. Our results indicated that the quality of cakes can be reflected by the interfacial properties of protein dispersions and the structural properties of cake batters. In addition, our study has supplied a fundamental approach for food industrial applications (such as baked goods) based on egg white to achieve optimal properties of cakes. • Interfacial properties of yolk-contaminated egg white systems were investigated. • The negative effects of egg yolk on the foaming properties were demonstrated. • Bubble size in batters remarkably increased when yolk-contamination was increased. • High correlations among protein dispersions, batters and cakes were proved. [ABSTRACT FROM AUTHOR]

Egg yolk powder is a widely used functional food ingredient due to its beneficial physicochemical and nutritional properties. However, its utilization in food can be limited due to its relatively high lipid content and low water-solubility. To address this issue, a two-step processing method utilizing enzymatic treatment combined with subcritical fluid extraction was investigated in this study. This method effectively reduced lipid content and improved water-solubility of egg yolk powder. An alcalase enzyme concentration of 500 U/g, extraction temperature of 313.15 K, extraction time of 120 min and a solid-liquid ratio of 1:9 (g:mL) produced powder with 20% lipid content and 71% water-solubility. Enzymatic hydrolysis clearly enhanced subcritical fluid extraction efficiency. This was attributed to hydrolysis disrupting the structure of egg yolk particles and facilitating the release of enclosed lipid molecules and was confirmed by scanning electron microscopy and laser confocal microscopy. [Display omitted] • Low-fat (20%) egg yolk powder with high water solubility (71%) was developed. • Enzymatic hydrolysis combined with subcritical fluid extraction was used. • Enzymatic hydrolysis improved the water solubility. • The highest oil extraction efficiency was achieved using 500 U/g alcalase. • Disruption in egg yolk structure promoted oil release. [ABSTRACT FROM AUTHOR]

In this study, alginate/κ-carrageenan hydrogel beads were developed to encapsulate and release egg yolk immunoglobulin Y (IgY) under simulated gastrointestinal conditions. The effects of κ-carrageenan concentration on the encapsulation and loading efficiency of the hydrogel beads was assessed, as well as on their swelling and release behavior in a simulated human gut. An κ-carrageenan concentration of 0.30% gave the optimum encapsulation and loading efficiency. After incubation in simulated gastric fluids, there was no loss in IgY activity when it was encapsulated within alginate/carrageenan beads but around 35% loss when it was encapsulated in pure alginate beads. This effect was attributed to a stronger electrostatic attraction and a more closely packed biopolymer network formed within the composite beads, based on measurements of their electrical and microstructural properties. The composite beads were resistant to swelling in the stomach phase, but not in the intestine phase. The kinetics of swelling under simulated gastric conditions was found to follow Schott's second-order model. The gastrointestinal digestion of the IgY was slower in the composite beads than in the pure alginate beads. The release kinetics of IgY from the composite beads was fitted by an irregular release model. Our results suggest that alginate/κ-carrageenan composite beads are efficient carriers for the delivery systems of hydrophilic immunoglobins. Image 1 • A high encapsulation efficiency of IgY in alginate/carrageenan beads was achieved. • Alginate/carrageenan beads had a denser internal microstructure than alginate ones. • 0.3% carrageenan gave strong protection of IgY-loaded beads in gastric conditions. • Release kinetics of IgY from beads was fitted best by an irregular release model. [ABSTRACT FROM AUTHOR]

In this study, the method of subcritical fluid-propane extraction (SPE) used to coproduce egg yolk oil (EYO) and low-fat egg yolk powder from spray-dried egg yolk powder (EYP) was investigated. Results showed that the optimum parameters were: extraction temperature of 313.15 K, extraction time of 120 min, and solid-liquid ratio of 1:9 (g/mL). Under this condition, the residual oil rate of EYP was 21.04%, which was much lower than that of ethanol extraction (39.24%). Scanning electron microscopy reveled that serious disruptions of egg yolk sphere extracted by SPE were observed, facilitating the EYO extraction. In addition, oil extracted by SPE had lower acid value and peroxide value than that of ethanol extraction. Moreover, the emulsifying properties and solubility of low-fat EYP obtained by SPE were similar to the original egg yolk powder. This study provides a new technique for coproducing high-quality oil and protein. Image 1 • SPE was used to coproduce yolk oil and low-fat dried egg yolk powder. • Yolk sphere was severely damaged and released more lipids under SPE. • Compared to ethanol extraction, EYO extracted by SPE had better oil quality. • The emulsifying properties and solubility of LYP-P were similar to OYP. [ABSTRACT FROM AUTHOR]

In this study, the interactions between egg yolk granule and soybean lecithin and their emulsion properties were investigated. For egg yolk granule, the increase of solubility and negative zeta-potential and decrease of hydrophobicity could be observed with the increase of lecithin concentrations, indicating the interactions between granule protein and lecithin. Results from the z-average particle size and the AFM image showed that the increase of solution pH and addition of lecithin could destroy the aggregated structure of the egg yolk granule. The disrupted granule exhibited better emulsion stability than that of native granule due to the higher surface charge and lower particle size. Notably, appropriate addition of lecithin (less than 0.25%) would be conducive to the formation of high stable emulsions by modestly reducing the contact angle, while extra lecithin (more than 0.50%) would induce excessive substitution of granule protein by competitive adsorption, leading to destabilization of the O/W emulsions via surfactant-induced depletion flocculation. Image 1 • The increase of solution pH and addition of lecithin could dissociate the egg yolk granule. • Dissociation of egg yolk granule was beneficial to emulsion stability. • Excessive displacement of interface granule proteins by lecithin resulted in stratification. [ABSTRACT FROM AUTHOR]

This study investigated the effects of heat treatment (at 72, 76, 80, 84 °C for 2, 4, 6, 8, 10, 12 min) on the rheological, microstructural, protein structures and 3D printing characteristics of egg yolk. The results showed that the storage modulus (G′), loss modulus (G″) and viscosity exhibited an increasing trend with increasing heating time. Confocal laser scanning microscope (CLSM) showed that after heating for 8 min at 76 °C, 80 °C and 84 °C, lipids were released from viscous yolk paste, followed by second recombination and aggregation among yolk components. At these points above, the solid behaviors (G' ≥ G″) of egg yolks were observed, which caused a restraint of proton migration of water and lipid. Fourier transform infrared spectroscopy (FTIR) demonstrated that after heating at 72 °C for 8 min, 76 and 80 °C for 6 min and 84 °C for 4 min, a left shift began to appear in the heat-induced egg yolk paste at wavenumber 1631 cm−1, which were in accordance with a decrease in the shorter relaxation time (T 21) and fluorescence intensity and an increase in apparent viscosity of egg yolks. The results of printing performance showed that the viscous yolk pastes induced by heat treatment (at 76 °C for 8 and 10 min or 80 °C for 6 min) can be used for 3D printing. Image 1073 • Heat-induced egg yolk paste can be used for 3D printing without additives. • LF-NMR, FTIR was used to reveal protein, lipid and water mobility and hydrogen bond. • Best printing performance of yolk was obtained by heat treatment at 76 °C for 8 min. • HDL plays a particular role in the formation of high-viscous heat-induced egg yolk. • Relationship between rheology, protein structure and printing behavior was analyzed. [ABSTRACT FROM AUTHOR]

The physicochemical properties, rheology, texture, water state and microstructure of gels formed from different ratio of egg proteins and soybean protein isolate were investigated. Results showed that composite solution that contained 75% egg proteins had the highest protein surface hydrophobicity while the biggest solubility was found when the proportion of egg proteins was 25%. Solid content and total sulfhydryl groups content before centrifugation increased as the proportion of egg proteins raised while total sulfhydryl groups content after centrifugation had less fluctuations because of the changes of protein solubility. Egg proteins-soybean protein isolate composite solutions had various growth ratio of G' during different stages of solution-gel transition process, suggesting the composition of the solutions affected the molecular interactions and then changed the gelling properties. Besides, composite gels that contained the whole egg had higher hardness and lower springiness than those gels that contained egg yolk. The gel hardness after 50% addition of the whole egg and egg yolk was about 561% and 329% of the original gel strength while the gel springiness was 0.91 and 0.94, respectively. From results of microstructure, egg yolk-soybean protein isolate composite gels possessed denser gel network, which may be related with higher solid content of egg yolk. Conversely, the whole egg-soybean protein isolate composite gels showed rigid fiber network with holes, leading to better water mobility, higher hardness and lower springiness. Image 1 • Properties of gels made with egg proteins and soybean protein isolate were studied. • The interaction between proteins promoted the exposure of hydrophobic groups. • Adding egg proteins is a good way to increase gels' hardness and keep springiness. • Egg proteins, especially egg yolk, increased the water stability of composite gels. [ABSTRACT FROM AUTHOR]

Egg yolk is an indispensable ingredient in the preparation of food emulsions due to its unique nutritional value and functional properties. However, egg yolk is sensitive to heat treatment and has poor emulsifying stability, which can be a limitation to the application of egg yolk in food industry. This study, the effect of neutral and alkaline protease (2,000U/g egg yolk protein) on thermal stability and emulsifying properties of egg yolk was investigated. Results showed that the hydrolysed egg yolk had higher thermal stability and emulsifying stability, especially for the samples hydrolysed by alkaline protease. The molecular weight of hydrolysed egg yolk protein was smaller than others as proved by electrophoresis and a considerable increase of protein solubility was observed. In addition, hydrolysis changed the degree of ionization of amino acids, increasing its static charge. The smaller molecular weight of the protein and the higher electrostatic charge delayed the gelation point, improving the thermal stability of the egg yolk. The emulsifying stability of hydrolysed egg yolk was improved, possibly resulting from the increase of soluble protein or polypeptide. Emulsions made with hydrolyzed egg yolk exhibited smaller particle sizes and higher surface charges, thus improving creaming stability of emulsions. Image 1 • Hydrolysis increased solubility by increasing net charge of egg yolk protein. • Hydrolysis improves heat resistance of egg yolk. • Hydrolysis increases creaming stability of egg yolk stabilized emulsions. • Alkaline protease has the best improvement effect on heat and emulsion stability. [ABSTRACT FROM AUTHOR]

The effects of sodium tripolyphosphate and sugar on cold-set gel properties of egg yolk/κ-carrageenan/xanthan gum mixed dispersions were investigated by zeta potential, rheological measurements, gel textural analysis and low-field nuclear magnetic resonance (LF-NMR). As the yolk content increased to the 5 g/100 mL in aqueous systems, phase separation of mixed gel could be observed, due to the relatively rough gel appearance. Furthermore, the addition of phosphate could significantly improve the phase separation of mixed gels by elevating the pH and reducing zeta potential. The increase in the content of yolk and sugar brought an enhancement in gel storage modulus, while the addition of phosphate induced a dramatic decrease in the gelation rate of mixed gels. Textural analysis confirmed that hydrogen bonding interaction was the important force, which determined gel strength of the ternary composite cold-set gelation system. The result of LF-NMR revealed that there was a negative correlation between the decrease of proton mobility of immobilization water and the increase of gel strength in different sample series. • The phase separation of composite gels could be improved by polyphosphate. • Changes in G′ and hardness of composite gels depend on the hydrogen bonds. • Gel strength has a strong relation with the proton mobility of composite gels. [ABSTRACT FROM AUTHOR]