Yolk Components Research Articles

Preparation of microgel particles from egg yolk components by combining phospholipase A2 with high-pressure homogenization: Physicochemical, structural properties and their effects on foaming, processing stability of egg white protein

In this study, two types of microgel particles from egg yolk components were prepared by combining enzymatic hydrolysis with high-pressure homogenization (HPH), and their differences in physicochemical properties, foaming properties, and microstructure were compared. Results showed that the particle size of both types of microgel particles had decreased from 2744.07 ± 408.26 nm (egg yolk, EY) to 144.97 ± 3.19 nm (PLA2 hydrolyzed egg yolk microgel particles, PYM) and 535.07 ± 46.07 nm (egg yolk microgel particles hydrolyzed by PLA2, YMP), from 736.24 ± 34.61 nm (EG) to 182.76 ± 4.12 nm (PLA2 hydrolyzed egg yolk granules microgel particles, PGM) and 443.98 ± 27.09 nm (egg yolk granules microgel particles hydrolyzed by PLA2, GMP). Besides, their interfacial adsorption abilities were significantly improved, reflected in the increase values in overrun, from161.90 % ± 9.84 % (EY) to 269.64 % ± 16.73 % (PMY) and 307.20 % ± 16.09 % (YMP), from 189.21 % ± 5.02 % (EG) to 280.38 % ± 36.05 % (PGM) and 261.91 % ± 34.03 % (GMP). Their structural properties showed higher stabilities after treatments. When the microgel particles are applied to cakes, the specific volume was increased from 2.05 ± 0.1 mL/g (EY) to 2.25 ± 0.13 mL/g (PYM) and 2.45 ± 0.03 mL/g (YPM), and from 2.00 ± 0.09 mL/g (EG) to 2.51 ± 0.13 mL/g (PGM) and 2.75 ± 0.21 mL/g (GMP), respectively. The hardness and chewiness were reduced with both types of microgel particles from egg yolk components, which indicated their potential value as edible foam stabilizers in the baking industry.

Salt induced slowdown of kinetics and dynamics during thermal gelation of egg-yolk.

We investigated the effect of the NaCl concentration (0.3-2M) on the structure and dynamics of hen egg yolk at room temperature and during thermal gelation at temperatures in the range of 66-90 °C utilizing low-dose x-ray photon correlation spectroscopy in ultra-small angle x-ray scattering geometry. With an increase in the salt concentration, we observe progressive structural and dynamic changes at room temperature, indicating the disruption of yolk components such as yolk-granules and yolk-plasma proteins. Temperature- and salt-dependent structural and dynamic investigations suggest a delay in the gel formation and aggregation of yolk low-density lipoproteins with increasing ionic strength. However, the time-temperature superposition relationship observed in all samples suggests an identical mechanism underlying protein aggregation-gelation with a temperature-dependent reaction rate. The sol-gel transition time extracted from kinetic and dynamic information follows Arrhenius's behavior, and the activation energy (460kJ/mol) is found to be independent of the salt concentration.

Effects of maternal supplementation with DHA and/or egg yolk powder on monoamine homeostasis in the perinatal piglet brain

ABSTRACT Objectives Reports indicate that children of mothers who received docosahexaenoic acid (DHA) or egg yolk supplements during pregnancy have improved performance on cognitive tasks and brain growth; their combination has recently been demonstrated to modulate functional neuronal network connectivity in the human-relevant piglet brain. To expand upon this functional connectivity analysis, neurochemical evaluation to determine how dietary supplementation with one or both of these nutrients during the last trimester of pregnancy alters monoamine homeostasis in selected brain regions of piglets was done. Methods Beginning gestation days 60–69 through weaning, pregnant sows were fed either control diet or diets supplemented with egg yolk powder, DHA, or both. Brains were then collected, and monoamine neurotransmitters and their metabolites were quantified from various brain regions with HPLC-ECD. Results Relative to controls, egg yolk supplementation increased serotonin metabolite (5-HIAA) levels in the cerebellum, while DHA supplementation decreased serotonin (5-HT) levels in the prefrontal cortex; combined supplementation increased norepinephrine metabolite (MHPG) levels in the prefrontal cortex and cerebellum, but decreased 5-HT levels in the posterior hippocampus. Notably, all diets increased serotonin, dopamine, and their respective metabolite levels in the substantia nigra. Disscussion This suggests both overlapping and specific effects of DHA and components of egg yolk in the context of maternal supplementation during pregnancy and lactation that might facilitate optimal neurodevelopment, with the nigrostriatal pathway being particularly sensitive. Such supplementations might impact brain function and facilitate development later in life through modulating monoamine homeostasis.

Comparative analysis on the properties of egg yolk lipids extracted by different extraction methods.

Egg yolk lipids are important components in egg yolk. Compared with proteins, minerals, vitamins and pigments in egg yolk, there is a lack of systematic research on extraction methods and characteristics of yolk lipid. Therefore, in this study, the extraction of egg yolk lipids by supercritical CO2 fluid extraction (SFE), subcritical propane extraction (SPE) and ethanol solvent extraction (SE) was studied, and the differences in composition and physicochemical properties of the three yolk lipids were analyzed. The egg yolk lipids extracted by SFE had the advantages of high unsaturated fatty acid content, low saponification value, acid value, peroxide value, and high content of neutral lipids such as triglyceride and cholesterol, but the polar phospholipids were completely retained in the yolk powder. The efficiency of lipid extraction of SPE was the highest among all the three methods, but the extraction capacity to the polar phospholipid was in the middle of the three methods. The efficiency of lipid extraction of SE was low, but the extraction capacity to the polar phospholipid was the highest. Suitable extraction methods could be selected based on the specific application requirements of egg yolk lipids and low-fat egg yolk powders.

Foaming and structural properties of egg yolk components microgel particles and their adsorption characteristics at the air-water interface

In this study, microgel particles of egg yolk and its components were constructed by inducing and modifying their structure via the high-pressure homogenization (HPH). In order to compare their structural characterization and reveal their adsorption mechanism at the air-water interface, yolk components were also combined with egg white protein (EWP) to achieve their microgels for investigation. Results suggested that after HPH, foam stabilities of egg yolk protein microgel (EYM) and egg yolk plasma microgel (EPM) were significantly improved, whereas no significance occurred on egg yolk granules microgel (EGM). Interestingly, after HPH, the adsorption capacity of the microgels from combination of yolk components and EWP exhibited a significant increasing trend. However, their interfacial adsorption stability was poor. Fluorescence spectrum and surface tension revealed that more hydrophilic groups and lower surface tension would occur on EY and EP after HPH, whilst no significant effects would happen on EG, which was consistent with the results of foaming characteristics. SDS-PAGE exhibited that there was no obvious change in the protein bands of egg yolk and its components, indicating that egg yolk and component proteins did not undergo covalent crosslinking or degradation with HPH treatment. In summary, our study prepares for the first time of the microgel particles from egg yolk components for stabilizing the air-water interface. In addition, we have revealed the relationship between the physicochemical properties, microstructures and interfacial adsorption properties of the microgel particles from egg yolk components, and have explored their mechanisms in depth.

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.

A Novel Approach for the Production of Mildly Salted Duck Egg Using Ozonized Brine Salting.

Salted eggs are normally produced by treating fresh duck eggs with a high salt concentration in order to acquire distinctive features and excellent preservation capabilities as a result of a series of physicochemical changes. This method, however, induces a high salt content in the product. The goal of this research was to create a new way of producing mildly salted duck eggs using ozonized brine salting. The brine was made by dissolving NaCl (26% w/v) in water or ozonized water at a concentration of 50 ng ozone/mL (ozonized brine). Compared to brine, ozonized brine resulted in salted eggs with reduced ultimate salt levels in both albumen and yolk (p < 0.05). The Haugh unit of the salted eggs generated by ozonized brine was similar to that of the brine-made salted egg group (p > 0.05), but the salted egg produced by ozonized brine matured and solidified faster because the yolk index (0.62) was higher than that of the brine (0.55) (p < 0.05). The final pH of salted eggs generated with brine and ozonized brine was not different (p > 0.05). Regardless of the salting method, both salted eggs contained low TVB-N content (<10 mg/100 g). Ozonized brine increased the protein carbonyl content in salted albumen, which may be related to albumen protein aggregation and served as a salt diffusion barrier. However, after boiling the salted egg, the protein carbonyl level was comparable to that of fresh albumen. The TBARS levels of boiled salted albumen prepared with brine and ozonized brine were comparable (p > 0.05), and the value was extremely low (~0.1 mg MDA equivalent/kg). The TBARS value of the salted yolk prepared with brine was higher than that of the salted yolk prepared with ozonized brine (p < 0.05), and both salted yolks showed increased TBARS values after cooking (p < 0.05). The albumen and yolk components appeared to be altered similarly by both brine and ozonized brine, according to the FTIR spectra. Furthermore, the appearance and color of the yolk and albumen in salted eggs prepared with brine and ozonized brine were comparable. Boiled salted albumen produced with ozonized brine had a denser structure with fewer voids. This could be attributed to the final salted egg's lower salt content and lower salt diffusion rate, which were likely caused by protein oxidation and, as a result, aggregation when ozonized brine was used.

Assessment of whole egg fractionation by tangential flow filtration: The problem of low-density lipoprotein aggregates

Eggs are a compelling source of bioactive compounds. Membrane separation is a green technology that allow components to be obtained while preserving their biological activity. The objective of this study was to assess the application of membrane separation technology to egg products. Whole egg plasma, egg yolk plasma and egg white were tangential flow filtrated evaluating the effect of the pore size and membrane materials. Transmission of dry matter and proteins from feed to filtrate was noticed in all the processes. Nevertheless, cholesterol and carotenoids were not detected at filtrates from 750 kDa to 0.2 µm when mixed ester or polyethersulfone were the membrane materials. The interactions between egg yolk and egg white components difficult the separation. Cholesterol was part of low-density lipoproteins. These lipoproteins together with carotenoids were filtrated with modified polyethersulfone at a minimum pore size of 0.2 µm. High uncertainty was obtained due to low-density lipoproteins aggregation. Three kinds of aggregates can justify these results: low-density lipoproteins aggregated themselves, low-density lipoproteins bound to ovomucin and other smaller egg white proteins (<750 kDa), and low-density lipoproteins bound only to smaller egg white proteins. The detected chelate effect of egg white proteins could be important in vivo. Therefore, research should be led to assess the influence of cooking method and digestion of the different egg components on the bioaccessibility of nutrients and the generation of bioactive peptides. Moreover, the filtration processes analysed herein may be useful techniques for liquid food matrix studies.

Research Note: Integrated proteomic analyses of chicken egg yolk granule

Chicken egg yolk granules (EYG) were the precipitated component of egg yolk after water dilution and centrifugation. Compared with egg yolk, EYG are rich in proteins, phospholipids, and minerals. In this study, an integrated proteomic analysis was carried out to in-depth mapping of the proteome, phosphoproteome, and N-glycoproteome of EYGs. After hydrolysis of the EYG total protein, the hydrolyzed peptides or the enriched phosphopeptides/glycopeptides were identified by liquid chromatography-tandem mass spectrometry. A total of 125 phosphorylation sites from 36 phosphoproteins and 244 N-glycosylation sites from 100 N-glycoproteins were identified in EYG. All 3 vitellogenins (precursors of egg yolk high-density lipoprotein) were heavily phosphorylated and N-glycosylated, of which 37 phosphorylation sites and 32 N-glycosylation sites were identified on vitellogenins-2. A Total of 30 N-glycosylation sites were identified on apolipoprotein-B (precursor of egg yolk low-density lipoprotein), but no phosphorylation site was identified. These phosphorylation and N-glycosylation of EYG proteins provide new insights for understanding the assembly structure and functional characteristics of EYG, thus contributing to its development and utilization.

Vitellogenin uptake activity in the intestinal ducts of intraovarian embryos in a viviparous teleost Xenotoca eiseni

In the viviparous teleost species belonging to the family Goodeidae, intraovarian embryos absorb maternal supplements while they grow during the gestation period. They take up the components via trophotaeniae, a hindgut-derived placental structure. Our previous study using a goodeid species Xenotoca eiseni revealed that intraovarian embryos absorb the yolk protein vitellogenin (Vtg) via the trophotaenia. However, another group indicated yolk components accumulate in the intestinal lumen of X. eiseni embryos. Here, we investigated whether the intestinal duct is capable of protein uptake, as is the trophotaenia. Immunohistochemical studies indicated that endogenous vitellogenin is detected in the intestinal epithelial cells of the intraovarian embryo. Tracer analysis using FITC-Vtg also indicated that intestinal tissues can take up protein. The endocytosis-related genes expressed in trophotaenia were also detected in the intestinal tissues of the embryo. Lipid transporter genes which are not expressed in the trophotaenia were detected in the embryonic intestine. This evidence suggests that the intraovarian embryo of X. eiseni possesses two distinct sites for uptake of the maternal proteins. However, the presumed functions of the embryonic intestine and trophotaenia might be not identical. The study provides a new perspective on how mother-to-embryo matrotrophic interactions have changed in the evolution of viviparous teleosts.

The changes of umami substances and influencing factors in preserved egg yolk: pH, endogenous protease, and proteinaceous substance.

The study investigated the changes of nucleotides, succinic acid, and free amino acids amounts in yolk and the causes leading to the changes after pickling to uncover the fundamental umami component of preserved egg yolk. The findings demonstrated that while the contents of 5′-adenosine monophosphate (AMP), 5′-cytidine monophosphate (CMP), 5′-guanosine monophosphate (GMP), 5′-uridine monophosphate (UMP), and succinic acid increased after slightly decreasing aspartic acid (Asp) content in preserved egg yolk increased gradually. The contents of 5′-inosine monophosphate (IMP) and other free amino acids were gradually decreased. Comparing the taste activity value (TAV), it was found that the single umami substance, succinic acid, played a key role in inducing the umami taste. In combination with the Spearman correlation analysis, it was shown that the proteinaceous substance, which is the most significant umami component in preserved egg yolk, tended to condense first and subsequently disintegrate in an alkaline environment. The orthogonal partial least squares analysis (OPLS) found that pH was also affected by the changes in proteinaceous substance. These findings offer suggestions for enhancing the pickling procedure and investigating the optimal pickling period for preserved eggs.

Dietary yolk supplementation decreases rates of yolk deposition in Japanese quail.

Generation of egg yolk by birds requires the synthesis and deposition of large amounts of protein and lipid, and is often accompanied by the incorporation of additional physiological mediators. While there has been much work examining the relative quantities of yolk components, as well as potential adaptive patterns of their allocation, we still do not have a full understanding of what controls yolk formation and composition. Once ovarian follicles are recruited into the preovulatory hierarchy, the yolk is deposited in concentric rings, with one ring deposited per day. Previous studies have shown that there is substantial interspecific and intraspecific variation in the number of rings in yolks, and thus the number of days it took those yolks to grow. We hypothesized that the ability to grow follicles to maturity quickly is limited by the availability of materials to make yolk precursors in the female, either in body reserves or in dietary access. To test this, we supplemented the diets of Japanese quail with hard-boiled chicken yolk and examined the influences of treatment and female body condition on follicle growth rates. Contrary to predictions, females with higher body condition indices produced yolks that grew more slowly, and yolks from supplemented birds grew more slowly than controls. These results indicate that females can modulate the rate of yolk incorporation into developing follicles, and that an energy balance that is too high may not be optimal for the fast growth of developing ovarian follicles.

Stability of low density lipoprotein particles affect the formation of off-flavor in thermal egg yolk

This study aimed to investigate the role of stability of low density lipoprotein (LDL) spherical particles as well as oxidation of lipids and proteins on formation of off-odor in heated egg yolk (EY). Off-odor attributes and volatile components of EY with different thermal temperature (25 °C–90 °C) were investigated by sensory evaluation, gas chromatography-mass spectrometry (GC–MS) and GC-ion mobility spectrometry (IMS). The off-flavor and volatile compounds increased significantly when EY were heated at 60 °C–65 °C. Destruction of LDL particle structure was presented by confocal laser scanning microscopy with thermal treatment at 60 °C. A positive correlation (r = 0.899, p < 0.05) was shown between oil exudation and off-odor of heated EY. Moreover, oxidation of lipids and proteins, protein aggregation, and changes of protein secondary structure (increased β-sheets and decreased α-helices) in LDL particles were all found when heating temperature rose to 65 °C. It was speculated that unstability of LDL particles resulted in the leakage of lipids; then oxidative products of lipids took part in the formation of off-odor volatiles in heated EY.

Egg components reverse the atrophy induced by injury in skeletal muscles.

Skeletal muscle atrophy is the loss of muscle tissue caused by factors such as inactivity, malnutrition, aging, and injury. In this study, we aimed to investigate whether egg components exert inhibitory effects on muscle atrophy. An egg mix solution was orally administered for 10 consecutive days to male C57BL/6J mice injected with cardiotoxin in the tibialis anterior (TA) muscle. The administration of egg mixture significantly decreased the atrogin-1 and MuRF-1 protein levels, key factors in muscle atrophy, as observed by western blotting. Furthermore, we investigated the effects of egg components such as avidin, lecithin, biotin, 3-sn-phosphatidylcholine, and L-α-phosphatidylcholine on dexamethasone (DEX)-treated C2C12myotubes. Lecithin, biotin, 3-sn-phosphatidylcholine, and L-α-phosphatidylcholine in egg yolk significantly recovered the diameters of C2C12myotubes decreased upon DEX application. Avidin did not show such reversal. Biotin, 3-sn-phosphatidylcholine, and L-α-phosphatidylcholine also attenuated atrogin-1 protein expression enhanced by DEX. Our findings reveal that egg yolk components could contribute to the reversal of skeletal muscle atrophy induced by muscle injury.

Characterization and Gene Expression of Vitellogenesis-Related Transcripts in the Hepatopancreas and Ovary of the Red Swamp Crayfish, Procambarus clarkii (Girard, 1852), during Reproductive Cycle

The major component of the animal egg yolk is the lipoglycoprotein vitellin, derived from its precursor vitellogenin (VTG), which is produced species-specifically in decapod crustaceans in the hepatopancreas and/or in the ovary of reproductive females. Previous studies on Procambarus clarkii vitellogenesis report the existence of two single VTGs. Here, from a multiple tissue transcriptome including ovaries and hepatopancreas of P. clarkii, we characterized four different VTG and two VTG-like transcriptomes encoding for the discoidal lipoprotein-high density lipoprotein/β-glucan binding protein (dLp/HDL-BGBP). The relative expression of the various genes was evaluated by quantitative Real-Time PCR in both the ovary and hepatopancreas of females at different reproductive stages (from immature until fully mature oocytes). These studies revealed tissue-specificity and a reproductive stage related expression for the VTGs and a constitutive expression in the hepatopancreas of dLp/HDL-BGBP independent from the reproductive stage. This study may lead to more detailed study of the vitellogenins, their transcription regulation, and to the determination of broader patterns of expression present in the female hepatopancreas and ovary during the vitellogenesis. These findings provide a starting point useful for two different practical aims. The first is related to studies on P. clarkii reproduction, since this species is highly appreciated on the market worldwide. The second is related to the study of new potential interference in P. clarkii reproduction to delay or inhibit the worldwide spread of this aggressively invasive species.

Natural variation in yolk fatty acids, but not androgens, predicts offspring fitness in a wild bird

BackgroundIn egg-laying animals, mothers can influence the developmental environment and thus the phenotype of their offspring by secreting various substances into the egg yolk. In birds, recent studies have demonstrated that different yolk substances can interactively affect offspring phenotype, but the implications of such effects for offspring fitness and phenotype in natural populations have remained unclear. We measured natural variation in the content of 31 yolk components known to shape offspring phenotypes including steroid hormones, antioxidants and fatty acids in eggs of free-living great tits (Parus major) during two breeding seasons. We tested for relationships between yolk component groupings and offspring fitness and phenotypes.ResultsVariation in hatchling and fledgling numbers was primarily explained by yolk fatty acids (including saturated, mono- and polyunsaturated fatty acids) - but not by androgen hormones and carotenoids, components previously considered to be major determinants of offspring phenotype. Fatty acids were also better predictors of variation in nestling oxidative status and size than androgens and carotenoids.ConclusionsOur results suggest that fatty acids are important yolk substances that contribute to shaping offspring fitness and phenotype in free-living populations. Since polyunsaturated fatty acids cannot be produced de novo by the mother, but have to be obtained from the diet, these findings highlight potential mechanisms (e.g., weather, habitat quality, foraging ability) through which environmental variation may shape maternal effects and consequences for offspring. Our study represents an important first step towards unraveling interactive effects of multiple yolk substances on offspring fitness and phenotypes in free-living populations. It provides the basis for future experiments that will establish the pathways by which yolk components, singly and/or interactively, mediate maternal effects in natural populations.

Emulsifying properties of plasma fractionated from egg yolk using low centrifugal forces—Mayonnaise preparation

Egg yolk can be fractionated into two fractions, plasma and granule, at high centrifugation force. This work was designed to study the influence of using low centrifugal forces (2000 to 6,000 ×g) for a short time (5 min) on the fractionation efficiency. The chemical composition and emulsifying properties (oil droplet size and stability against creaming) of fractionated plasmas were also investigated. The results showed that the separation efficiency of granules was significantly increased with increasing centrifugal force. No significant difference was found in emulsifying properties of plasmas fractionated at all centrifugal forces compared to whole egg yolk. Plasma fractionated at 5,000 and 6,000 ×g was further applied for mayonnaise preparation. Mayonnaises prepared from plasmas showed no significant difference in the rheological and colorimetric properties compared to whole egg yolk. Plasma prepared from low centrifugal force, compatible to industrial setting, maintains its original emulsifying properties and is applicable for mayonnaise preparation. Novelty impact statement Although many years of research on fractionation of egg yolk fractions, industrial application of egg yolk fractions is rare. Literature information on this field was relied on high centrifugal forces of fractionation. The conditions we applied using low centrifugation forces are thus significant to help the industry realize the potential of value-addition to egg yolk component such as phosvitin in the granule while using the plasma fraction for its emulsifying property. The obtained results suggested that plasma prepared using low centrifugal forces showed comparable rheological properties and was applicable for preparing mayonnaise, which indicates its potential in future industry application.

Effects of extruded, milled, and whole flaxseed (Linum usitatissimum) on egg performance, lipid components, and fatty acids concentrations in yolk and blood, and antioxidant system of commercial laying hens

This study evaluated the effects of three inclusion levels (3, 6, and 9%) of different processing types of flaxseed (no processing, milled and extruded) on egg performance, egg yolk fatty acids (FAs), and lipids components in yolk and blood of Hy-Line W-36 75-week-old for nine weeks. We allocated 300 laying hens to ten treatments, including control and three inclusion levels (3, 6, and 9%) of three processed methods (whole, WF; milled, MF; and extruded, EF). Each treatment had six replicates containing five hens each. Egg performance, Haugh unit, feed intake, and egg production increased concomitantly with enhancing the percentage of flaxseed in diets. In contrast, shell thickness, shell strength, yolk weight, feed conversion efficiency, and egg mass remained unchanged. Interestingly, the extrusion method had positive effects on egg weight, egg production, feed intake, and egg mass contents, unlike other groups. In respect of yolk FAs, as predicted, individuals fed the 9%EF (9.31 g/100 g) diet had the highest value of n-3 fatty acids. Consequently, n-6/n-3 ratio was improved from 9.20 g/100 g in the yolk of chicks fed the control diet to 1.26 g/100 g in hens fed the 9%EF diets. While cholesterol (CHO) in yolk, egg, and blood of hens fed 9%EF diet were significantly lower than control, total protein in blood was significantly higher than control (P < 0.05). Although superoxide dismutase in the blood of birds fed the control diet was significantly higher than those fed 9%EF diets, serological enzymes in laying hens were not affected by experimental diets. In conclusion, feeding birds with 9%EF significantly improved most of the egg quality parameters, FAs profile, blood factors, and antioxidant capacity. Therefore, extruded flaxseed up to 90 g/kg can be used as a useful method towards improving the productive performance of old laying hens in a commercial-scale study without impairing the antioxidant system and inducing liver damage.

Component resolved diagnosis of egg yolk is an indispensable part of egg allergy.

It was urgent to explain the role of egg yolk allergen sensitization to the egg allergic population and we would evaluate the diagnostic value of allergen components in whole eggs, including egg white and egg yolk. Firstly, we collected 99 positive and 21 negative sera against egg allergy. Then we used modified enzyme linked immunosorbent assay (ELISA) to survey specific IgE (sIgE) to all-proven and single component in eggs, Ovomucoid (Gal d 1), Ovalbumin (Gal d 2), Ovotransferrin (Gal d 3), Lysozyme C (Gal d 4), Serum Albumin (Gal d 5), and YGP42(Gal d 6) in allergic and non-allergic populations. Last but not least, we studied the sIgE reactivities to egg allergen components by receiver operating characteristic (ROC) analysis. Among egg-allergic individuals, nearly 10% were sensitized to five of six egg allergen components, and the cross-reaction frequency between two egg yolk allergens with Gal d 1 was about 30% in the groups diagnosed with egg allergy or non-allergy. The best component-combination diagnosis in egg allergy of Gal d 1+ Gal d 6 demonstrated the largest area under curve (AUC) of 0.994. Our results suggested that there were individual differences in allergenicity of different egg allergen components, especially in the samples negative to egg allergy diagnosed but sensitive to egg yolk components. It was indicated that component resolved diagnosis of egg yolk improved the value for egg allergy management indispensably.

Gelation inhibiting additives and freezing impact rheological, thermal, and microstructural properties of yolk

We investigated the effect of salt, sugar, and hydrolyzed egg yolk protein (HEY) on yolk's rheological properties, thermal behavior, and microstructure for a better understanding of their gelation inhibition mechanism. Salted yolk samples had the highest yield stress, followed by HEY and sugared yolk samples. With the addition of salt, the yolk's denaturation temperature and amount of free water significantly increased. Conversely, sugar and HEY had no significant impact on the thermal behavior of yolk components. Different additives caused pronounced differences in yolk's microstructure. The addition of salt resulted in dissociation of proteins and a concomitant increase in the number of small particles. Sugar and HEY presumably interacted with proteins and rearranged them into stable clusters. Freezing time also impacted the rheological, thermal, and microstructural properties of yolk in the presence of the additives. With prolonged freezing time, the tendency to undergo gelation increased. The salted yolk sample had significantly increased amount of non-freezable water, while no changes were observed in sugared and HEY yolk samples. The size and clustering of the particles varied during prolonged freezing. Interestingly, frozen-thawed yolks with additives regained their fluidity during refrigeration. Overall, salt, sugar and HEY effectively inhibited gelation, albeit, through different mechanistic processes.