Effects of strong alkali treatment on the physicochemical properties, microstructure, protein structures, and intermolecular forces in egg yolks, plasma, and granules

Effect of salting and dehydration treatments on the physicochemical and gel properties of hen and duck egg yolks, plasma and granules

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.

Epigallocatechin gallate modification of physicochemical, structural and functional properties of egg yolk granules

The aim of this study was to prepare protein-polyphenol covalent complexes by treating egg yolk granules (EYG) with alkali in the presence of epigallocatechin gallate (EGCG) and characterize the physicochemical, structural, and functional properties of these covalent complexes. Results revealed that the optimal covalent binding occurred when the concentration of EGCG reached 0.15% (w/w), resulting in a grafting rate of 1.51 ± 0.03%. As the amount of EGCG increased, corresponding increases were observed in the particle size and ζ-potential of the complexes, thereby enhancing their stability. Furthermore, our analysis using fluorescence spectroscopy, FTIR, SEM, and SDS-PAGE collectively demonstrated the formation of a covalent complex between EYG and EGCG. Notably, the covalent complexes exhibited improved antioxidant activity and emulsifying properties. Overall, this study establishes a theoretical framework for the future practical application of EYG, emphasizing the potential of EGCG to modify its structural and functional characteristics.

Molecular regulation of rapeseed protein for improving its techno-functional properties

To improve the techno-functional properties of rapeseed protein (RP), this work tried to regulate the molecular structure of RP via inducing the co-assembly of RP with zein and whey protein (WP). The results showed that WP and zein mainly regulate the folding process of RP through hydrophobic and disulfide bonds, thereby altering the structural conformation and forming stable complex RP (CRP). WP addition not only increased the number of surface charges and hydrophilicity of proteins, but also decreased their sizes, improved the water solubility, as well as the availability of active groups. These changes significantly increased the foaming capacity (from 60 % to 147 %) and in vitro gastric digestion rate (from 10 % to 60 %) of CRP. Besides, WP also contributed to the formation of gels and the regulation of their textural profiles. Comparatively, zein improved the hydrophobicity of CRP and balanced degree of intermolecular forces, which effectively increased the emulsifying activity index of CRP from 22 m2/g to 90 m2/g. Zein decreased the hardness, springiness and water-holding capacity of gel, but increased its gumminess and chewiness. Overall, both WP and zein effectively changed the structural conformation of RP, and improved its techno-functional properties, which provides an effective strategy to modify protein.

Redistribution and fusion of protein-lipid assemblies within the egg yolk sphere under slight non-destructive deformation causing a change in thermal gel properties

Egg yolk production processed after separating egg white is a common method to shorten cycle, but its taste quality will change even the vitelline membrane is intact. This might be related to the slight non-destructive deformation causing redistribution and fusion of protein-lipid assemblies within the egg yolk spheres. We investigated the mechanism of the change in thermal gel properties under slight deformation. The results of microscopic structural morphology revealed that the whole boiled egg yolk (WEY) underwent a transition in protein-lipid assembly morphology within yolk spheres, which changed from local aggregation to disordered fusion in shaken boiled egg yolks (SEYs). The spectroscopic and physicochemical properties analysis demonstrated that the redistribution of protein-lipid assemblies gave rise to marked changes in water migration, texture properties, molecular interactions, and oral sensation simulation of egg yolk thermal gels. This is benefit to guide the regulation of the taste quality egg yolk products in industry.

Effects of different temperatures on the physicochemical characteristics, microstructure and protein structure of preserved egg yolk

To clarify the mechanism of lower temperatures promoted the solidification of preserved egg yolk, the effects of temperature (4 °C, 10 °C and 25 °C) on the physicochemical properties, microstructure and protein structure of preserved egg yolk were studied. Results showed that the exterior egg yolk (EEY) exhibited higher pH, hardness and free sulfhydryl content at low-temperature pickling. The microstructure showed that the EEY gradually formed a denser gel network structure at lower temperatures. Electrophoresis results and Fourier transform infrared spectroscopy (FTIR) indicated that there were different degrees of protein degradation and cross-linking of proteins in the IEY (the interior egg yolk) and EEY and the decrease of β-sheets in the secondary structure was accompanied by an increase of β-turns during the formation of egg yolk gels. These results indicated that egg yolk solidification was faster and denser gel structure at 4 °C and 10 °C.

Self-assembly and aggregation behavior of temperature-controlled modified glycinin and d-galactose colloidal particles

The molecular structure and morphologies of complex colloidal particles with modified glycine (S-11S) and d-galactose were studied by multispectral, microscopic imaging and chromatographic techniques at different temperatures, and the self-assembly and aggregation mechanisms were determined. Overall, high-temperature-treated S-11S and d-galactose associate at cysteine and phenylalanine sites and self-assemble into colloidal particles of greater stability than glycinin and S-11S via ionic and disulfide bonds. The structure and subunit content of composite colloidal particles were changed. Assessing the sub-microstructure reveals that temperature can regulate the directional aggregation of complex colloidal particles. The elasticity of the complex colloidal particles is maximum enhanced at 95 ℃ as confirmed by the rheological. Thus, the heat-treated aggregation of the soy protein and its complex was evaluated to provide a new theoretical basis for the application of soy protein in gels and other areas and contribute to the design of new soy protein products.

The effects of sucrose/NaCl combined pickling on the textural characteristics, moisture distribution, and protein aggregation behavior of egg yolk

Salted egg yolks have a tender, loose, gritty, and oily texture and are commonly employed as fillings in baked goods. This study investigated the formation mechanism of egg yolk gels using three different pickling methods: NaCl, sucrose, and mixed groups. The results revealed that of these pickling methods, egg yolks pickled with the mixture had the lowest moisture content (11.59% at 25°C and 10.21% at 45°C), almost no free water content, and the highest hardness (19.11 N at 25°C and 31.01 N at 45°C). Intermolecular force measurements indicated that pickling with the mixture mitigated the surface hardening effect of sucrose and facilitated protein cross-linking. Moreover, confocal laser scanning microscopy of the egg yolk gels pickled with the mixture displayed macromolecular aggregates and oil exudation, suggesting that this method partially disrupted the lipoprotein structure and notably promoted yolk protein aggregation and lipid release. Overall, egg yolks formed a dense gel via the mixed pickling method owing to the ionic concentration and dehydration effects. These findings show the impact of NaCl and sucrose in pickling egg yolks, providing a crucial foundation for developing innovative and desirable egg yolk products. PRACTICAL APPLICATION: This study introduces a novel pickling strategy that combines sucrose and NaCl for egg yolk processing. The egg yolk pickled using this method exhibited improved quality according to the evaluated textural characteristics, moisture distribution, and protein aggregation behavior. The findings may broaden the use of sucrose as a pickling agent for egg yolk processing and provide new ideas for developing and producing pickled eggs and other food products.

Effect of gamma-ray and electron-beam irradiation on the structural changes and functional properties of edible insect proteins from Protaetia brevitarsis larvae

Edible insects are regarded as future food sources to replace traditional livestock proteins. However, insect proteins have poor processing properties owing to various structural limitations. We investigated the structure of Protaetia brevitarsis larvae proteins modified by irradiation, and analyzed their resulting processing abilities. Following irradiation with gamma rays and electron beams, the ratio of parallel β-sheets to β-turns changed significantly, and changes in the tertiary protein structures were also confirmed. The polydispersity indices of the proteins remained relatively constant following irradiation, although the zeta potential and mean diameter changed. Furthermore, the pH, protein solubility, surface hydrophobicity, foaming capacity, and emulsion stability were higher than those of the control, whereas the viscosity and foaming stability were lower. Thus, gamma ray and electron beam irradiation clearly lead to changes in the structures of edible insect proteins and improves their processing properties, promoting the industrial utilization of such proteins in the food industry.

Tracking transformation behavior of soluble to insoluble components in liquid egg yolk under heat treatment and the intervention effect of xylitol

The heat sensitivity of egg yolk limits its application, and xylitol can improve its thermal stability. The soluble and insoluble components of egg yolk and egg yolk containing xylitol treated at different temperatures were explored from the aspects of thermal instability behavior characterization and structure property. Magnetic resonance imaging and low field nuclear magnetic resonance showed that increased temperature induced liberation and transfer of hydrogen protons. Meanwhile, the apparent viscosity of soluble components increased, while that of insoluble components decreased. Microstructure showed that heat treatment induced aggregation and lipid transfer. SDS-PAGE showed that heat treatment induced aggregation and transformation of γ-livetin and apo-LDL. The change in crystal structure, Raman spectroscopy, and 3D fluorescence spectra showed that heat treatment resulted in the unfolding of yolk proteins, especially plasma proteins. Xylitol could alleviate transformation of components by stabilizing protein structure, alleviating the damage in protein integrity and elevation in aggregation size.

Effects of CaCl2 on the structure of high-density lipoprotein and low-density lipoprotein isolated from rapidly salted separated egg yolk

According to previous research, adding CaCl2 to the salting solution improves the quality of salted separated egg yolk. To further understand the improvement mechanism of CaCl2, this paper investigated the effect of CaCl2 on the structure of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) during the salting process. The results indicated that the addition of CaCl2 can affect the composition of HDL and LDL apolipoproteins, improving the orderliness of the HDL structure and the looseness of the LDL structure. It was discovered by atomic force microscopy (AFM) that adding CaCl2 to the salting solution can weaken the aggregation behavior of HDL. Simultaneously, the addition of CaCl2 decreased the relative content of intermolecular β-sheets in the secondary structure of HDL and LDL, influenced their tertiary conformation, and prevented HDL and LDL from participating in the formation of a three-dimensional gel structure by influencing their hydrogen bonds and hydrophobic interactions.

Effects of CaCl2 on the rheology, microstructure and protein structures of rapidly salted separated egg yolk

Bivalent or trivalent metal salts can enhance the oil output and sandiness of salted eggs. We added CaCl2 to the salting solution to improve the quality of rapidly salted separated egg yolk and investigated its effect on rheological, microstructure, and protein structure. According to the findings, adding CaCl2 to the salting solution can promote the precipitation of egg yolk water, increase its viscosity, induce protein aggregation, and increase the denaturation temperature of the protein. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) revealed that the inner boundary of egg yolk salted with CaCl2 was clearer and that the number and size of salted egg yolk lipoprotein aggregates were larger than those of egg yolk salted without CaCl2. Analysis using Fourier transform infrared spectroscopy (FTIR) demonstrated that CaCl2 caused the interconversion of the secondary-level structure. CaCl2 can have an impact on the microenvironment of amino acid residues, according to the results of 3D fluorescence and UV absorption spectra. Therefore, adding CaCl2 can accelerate the loss of water and change the structure of lipoprotein in egg yolk, which improves the sandiness and oil yield of salted separated egg yolk.

Physical Characteristics of Egg Yolk Granules and Effect on Their Functionality

Eggs are among the most nutritious foods in the world, a versatile ingredient in many food applications due to their functional attributes such as foaming, emulsifying, and coloring agents. Many studies have been reported on egg yolk fractionation and characterization in the last decade because of its nutritional and health benefits, especially egg yolk granules. This has led to the development of new food products and packaging materials. However, the influence of their physical characteristics during processing significantly impacts the functionality of yolk granules. In this overview, the egg yolk, the granule fraction's separation, fractionation, components, and molecular protein structure are first presented. Secondly, recent studies on egg yolk granules published over the past decade are discussed. Furthermore, the application of the granules in different industries and current specific scientific challenges are discussed. Finally, it simplifies the changes in the physical characteristics of the granules during different treatment methods and the impact on the functionalities of the resulting products in the food (emulsifiers, edible films), pharmaceutical, and health (encapsulation systems and biosensors) sectors.

A review on the development of pickled eggs: rapid pickling and quality optimization

Pickled eggs enjoy a long processing history with unique flavor and rich nutrition but suffer from long pickling cycle due to the limitations of traditional processing methods. In terms of quality, salted egg whites have the disadvantage of high sodium content, and salted egg yolks have problems such as hard core and black circle around outer layer. Likewise, the quality of preserved eggs is challenged by the black spots (dots) on the eggshells and the high content of heavy metals in the egg contents. The sustainable development of traditional pickled eggs are hindered by these defects and extensive research has been carried out in recent years. Based on the elaboration of the quality formation mechanism of salted eggs and preserved eggs, this paper reviewed the processing principles and applications of rapid pickling technologies like ultrasonic technology, magnetoelectric-assisted technology, water cycle technology, vacuum decompression technology, and pulsed pressure technology, as well as the quality optimization methods such as controlling the sodium content of the salted egg whites, improving the quality of salted egg yolks, promoting the quality of lead-free preserved eggs, and developing heavy metal-free preserved eggs. In the end, the future development trend of traditional pickled eggs was summarized and prospected in order to provide theoretical guidance for the actual production.

Identification of candidate genomic regions for thermogelled egg yolk traits based on a genome-wide association study

Egg yolk texture is an important indicator for evaluating egg yolk quality. Genetic markers associated with economic traits predict genomes and facilitate mining for potential genes. Numerous genome-wide association studies have been conducted on egg traits. However, studies on the genetic basis of thermogelled yolk texture are still lacking. The aim of the present study was to find significant single nucleotide polymorphism (SNP) sites and candidate genes related to thermogelled yolk texture in Hetian Dahei chicken (HTHD) flocks that can be used as genetic markers. Five traits, including hardness, cohesiveness, gumminess, chewiness, and resilience, had low heritability (0.044-0.078). Ten genes, including U6, FSHR, PKDCC, SLC7A11, TIMM9, ARID4A, PSMA3, ACTR10, EML4, and SLC35F4 may control the hardness of the thermogelled egg yolks. In addition, 12 SNPs associated with cohesiveness were identified. RELCH located on GGA2 participates in cholesterol transport. The candidate gene LRRK2, which is associated with gumminess, influences the concentrations of very low-density lipoprotein in blood. Eight SNPs associated with resilience were identified, mainly on GGA3 and GCA28. In total, 208 SNPs associated with chewiness were identified, and 159 candidate genes, which were mainly involved in proteasome-mediated ubiquitin-dependent protein catabolic process, negative regulation of transport, lipid droplet organization, and vehicle docking involved in exocytosis, were found near these regions. Thermogel egg yolk texture is a complex phenotype controlled by multiple genes. Based on heritability assays and GWAS results, there is a genetic basis for the texture of thermogelled egg yolks. We identified a series of SNPs associated with yolk texture and candidate genes. Our result provides a theoretical basis for breeding high-quality egg yolk using molecular marker-assisted selection and could facilitate the development of novel traits.

The Quality Characteristics Formation and Control of Salted Eggs: A Review

Salted egg, a traditional characteristic processed egg product in China, is popular among consumers at home and abroad. Salted egg quality characteristics formation primarily includes the hydration of egg white, the solidification of egg yolk, the unique color and flavor of salted egg yolk, and the formation of white, fine, and tender egg whites and loose, sandy, and oily egg yolks after pickling and heating. The unique quality characteristics of salted eggs are mostly caused by the infiltration dehydration of salt, the intermolecular interaction of proteins, and the oxidation of lipids. In recent years, to solve the problems of salted eggs having high salinity, long production cycle, and short storage period, the pickling technology for salted egg has been improved and researched, which has played a significant role in promoting the scientific production of salted eggs. This paper summarizes the mechanisms of salted egg quality characteristics formation and factors influencing quality, with a perspective of providing a theoretical basis for the production of high-quality salted eggs.

Hollow protein microparticles formed through cross-linking by an Au3+ initiated redox reaction

Hollow microparticles (MPs) are of great relevance in the materials industry for a wide range of applications, such as catalysis, coatings, and delivery of theranostics. Here, we report the formation of hollow MPs through the assembly of lipoproteins in CaCO₃ templates. Proteins interact in the pores of CaCO₃ templates through attractive hydrophobic forces and form dense edges of hollow MPs. To further cross-link the proteins, Au³⁺ was added to initiate a redox reaction, where proteins were oxidized forming inter- and intramolecular covalent bonds, while Au³⁺ was reduced and gold nanoparticles (AuNPs) were formed. The obtained protein-based hollow MPs have a diameter of 6 μm and the AuNPs are embedded on their surface. Through this research, we suggest a new route to design biobased Au-protein hollow MPs in simple steps, which can allow new possibilities for carrying functional molecules and bioimaging.

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.

Janus effects of NaCl on structure of egg yolk granules

Egg yolk granules are supramolecular assembly of high-density lipoproteins and phosvitin driven by calcium bridges. However, applications of granules are severely restricted by the large particle size and poor water dispersibility. This study revealed the Janus effects of NaCl on structure of granules at varied pH values. Addition of 0.3-0.5 M NaCl led to the dissociation of at pH 5.0-7.0. At pH 5.0-10.0, dissociated granules demonstrated good colloidal stability with NaCl because of the adsorption of highly hydrated Na⁺ and Ca²⁺, which provided strong hydration repulsion when electrostatic repulsion was screened. In contrast, at pH 2.0 and 3.0, dissociated granules were positively charged with adsorption of poorly hydrated Cl^- as counterions. Cl^- failed to give sufficient hydration repulsion, leading to the phase separation with 0.3-0.5 M NaCl. Similar effects have been also found in LiCl, KCl, and CsCl, but Li⁺ might be less effective to disrupt calcium bridges.

Study on the mechanism of enhanced gel strength of heat-induced egg white by shikimic acid braising

This study evaluated the effects and mechanism of shikimic acid braising on the gelling characteristics of heat-induced egg white gel (HEWG). The results indicated that, during braising, soluble protein and hardness showed an overall increasing trend. The absolute Zeta potential value showed a decreasing trend; however, T₂ and free sulfhydryl group showed an increasing trend first and decreasing trend later, and surface hydrophobicity showed a decreasing trend. Microstructure analysis showed that protein gel aggregation increased and that holes and cracks formed first, and then the cracks decreased. Fourier transform infrared spectrometry showed that shikimic acid could strengthen the polarity of HEWG, and a mutual transformation occurred between intramolecular β-sheets, intermolecular β-sheets, and intermolecular antiparallel β-sheets, as well as a slight blue-shift, in the α-helices. In general, the addition of shikimic acid could alter the HEWG structure and improve its gel strength, polarity, and aggregation. Moreover, the higher the concentration of shikimic acid, the greater the influence on HEWG. Therefore, shikimic acid could be used as a new type of gel enhancer for the modification of egg white gel.

Effects of salt and heat treatment on the physicochemical properties, microstructure, secondary structure, and simulated in vitro gastrointestinal digestion of duck egg white

BACKGROUND

The texture and structure of the duck egg white (DEW) gel under salt and heat treatment are crucial to its digestibility. Specifically, the structural changes of food protein gels have been recognized for their potential to regulate in vitro digestion. In this study, the effects of gel characteristics and simulated in vitro gastrointestinal digestion of DEW under combined salt and heat treatment were investigated.

RESULTS

With the increase in salting time and temperature, a porous opaque gel with large particles was formed, the moisture content of DEW showed a downward trend, and the same was true for hardness changes. The microstructure suggested that, with the penetration of NaCl, DEW proteins were denatured, and the protein molecules gradually unfolded and then aggregated after 7 days. The secondary structure revealed that, as the salting time and temperature increased, the proportion of intermolecular β-sheets and α-helices decreased. In terms of in vitro digestion, the highest digestibility was obtained at 14 days of salting combined with 100 °C heat treatment, and the digestibility was the lowest when marinated for 7 days at 121 °C. Liquid chromatography and tandem mass spectrometry (LC-MS/MS) indicated that the number of different types of peptides and specific peptides was positively correlated with the salting time and temperature of the DEW at the end of gastric digestion.

CONCLUSIONS

Heat treatment at 100 °C has a higher in vitro digestibility than at 121 °C. Gels with low hardness, large pores, and rough textures are easier to digest by pepsin and release more peptides. © 2021 Society of Chemical Industry.

Comparative Study on Foaming Properties of Egg White with Yolk Fractions and Their Hydrolysates

As an excellent foaming agent, egg white protein (EWP) is always contaminated by egg yolk in the industrial processing, therefore, decreasing its foaming properties. The aim of this study was to simulate the industrial EWP (egg white protein with 0.5% w/w of egg yolk) and characterize their foaming and structural properties when hydrolyzed by two types of esterase (lipase and phospholipase A2). Results showed that egg yolk plasma might have been the main fraction, which led to the poor foaming properties of the contaminated egg white protein compared with egg yolk granules. After hydrolyzation, both foamability and foam stability of investigated systems thereof (egg white protein with egg yolk, egg white protein with egg yolk plasma, and egg white protein with egg yolk granules) increased significantly compared with unhydrolyzed ones. However, phospholipids A2 (PLP) seemed to be more effective on increasing their foaming properties as compared to those systems hydrolyzed by lipase (LP). The schematic diagrams of yolk fractions were proposed to explain the aggregation and dispersed behavior exposed in their changes of structures after hydrolysis, suggesting the aggregated effects of LP on yolk plasma and destructive effects of PLP on yolk granules, which may directly influence their foaming properties.

Impact of ozone-induced oxidation on the textural, moisture, micro-rheology and structural properties of egg yolk gels

The impact of ozone-induced oxidation on the gel properties of egg yolk was investigated for the first time in this research. The textural properties, water-holding capacity, cooking loss rate and color of the chicken egg yolk gel (CEYG) were significantly improved after ozonation. The maximum hardness value (976.04 g) was reached at 20 min of ozonation and it was 134.92 g higher than that of the natural group. Additionally, the ozone-treated yolk showed an increase of 58.47% in carbonyl content and a decrease of 44.33% in free sulfhydryl groups. The results of low-field nuclear magnetic resonance indicated that ozone promoted the conversion of free water to non-flowing water in the CEYG. Scanning electron microscopy represented that the moderate ozone treatment resulted in a more regular, continuous and smooth network structure of the CEYG. These results provided a theoretical basis for the application of ozone to improve the performance of heat-induced CEYG.

Kappa-carrageenan enhances the gelation and structural changes of egg yolk via electrostatic interactions with yolk protein

The effect of κ-carrageenan (κ-C) on yolk over heat-induced gelation at natural yolk pH (6.2) and natural whole egg pH (7.5) was studied. The results showed the zeta potential values changed from -2.3 to -31.3 mV, from -8.6 to -28.6 mV for native pH yolk and pH 7.5 yolk because of the κ-C addition, respectively. These results indicated electrostatic interactions formed between protein and κ-C. The average area of holes formed by yolk gelation increased by κ-C addition. The addition of 1.0% κ-C decreased the gelling points from 62.1 to 54.4 °C, from 64.5 to 61. 6 °C for native pH and pH 7.5 yolk, respectively. A schematic model was established to show that κ-C enhances the yolk properties via electrostatic interactions. And the Fourier transform infrared (FTIR) spectroscopy verified the formation of κ-C-protein interactions. This study provides a guidance for designing novel food systems containing yolk and κ-C.

Depolymerization of chicken egg yolk granules induced by high-intensity ultrasound

The effects of high-intensity ultrasound (HIU) treatment-induced depolymerization of chicken egg yolk granules were investigated. The results showed that the yolk granules were depolymerized after HIU treatment, and the average particle size was significantly reduced from 289.4 nm (untreated) to 181.4 nm (270-W HIU treatment). All contents of dry matter, protein, calcium and phosphorus in the supernatant of the HIU-treated yolk granule solution increased, which suggests that HIU treatment increases the dissolution of yolk granule components. Spectroscopic analysis showed that HIU treatment increased the polarity of the microenvironment and enhanced the hydrogen bond force of yolk granules. These changes induced by HIU treatment collectively enhanced the zeta potential, decreased the free sulfhydryl group content, and slightly improved the emulsifying activity index of yolk granules. The present study reveals the depolymerization effect of HIU treatment on egg yolk granules and can inspire new potential applications of egg yolk granules.

Gelation behavior of egg yolk under physical and chemical induction: A review

Gelation is one of the most important functional properties of egg yolk. High content and rich variety of protein and lipid in egg yolk are the material basis of gel formation. The natural structure of proteins in egg yolk is unfolded under treatments such as heat, alkali, salt, etc., thus causing the interactions between protein-protein and protein-lipid and forming the gel. Under different methods of induction, egg yolk is solidified to form different three-dimensional network structures. Different inducing methods exhibit different gel formation mechanisms. In this paper, the gelation behavior of egg yolk and its internal molecular agglomeration mechanism induced by heat, alkali, salt, freezing, high pressure, and salt-heating synergy were reviewed to provide a reference for further studies on the formation mechanisms and product development of egg yolk gel.

Application of volatile and spectral profiling together with multimode data fusion strategy for the discrimination of preserved eggs

The maturity level of eggs during pickling is conventionally assessed by choosing few eggs from each curing batch to crack open. Yet, this method is destructive, creates waste and has consequences for financial losses. In this work, the feasibility of integrating electronic nose (EN) with reflectance hyperspectral (RH) and transmittance hyperspectral (TH) data for accurate classification of preserved eggs (PEs) at different maturation periods was investigated. Classifier models based solely on RH and TH with EN achieved a training accuracy (93.33%, 97.78%) and prediction accuracy (88.89%; 93.33%) respectively. The fusion of the three datasets, (EN + RH + TH) as a single classifier model yielded an overall training accuracy of 98.89% and prediction accuracy of 95.56%. Also, 52 volatile compounds were obtained from the PE headspace, of which 32 belonged to seven functional groups. This study demonstrates the ability to integrate EN with RH and TH data to effectively identify PEs during processing.