The vitelline membrane: Dynamics of cholesterol metabolism in hens' eggs

Comparative N-Glycoproteomic Analysis Provides Novel Insights into the Deterioration Mechanisms in Chicken Egg Vitelline Membrane during High-Temperature Storage

The weakening of chicken egg vitelline membrane (CEVM) is one of the most important factors influencing egg quality during high-temperature storage. Therefore, a comparative N-glycoproteomic analysis of CEVM after 10 days of storage at 30 °C was performed to explore the roles of protein N-glycosylation in membrane deterioration. In total, 399 N-glycosites corresponding to 198 proteins were identified, of which 46 N-glycosites from 30 proteins were significantly altered. Gene ontology analysis revealed that these differentially N-glycosylated proteins (DGPs) were involved in antibacterial activity, glycosaminoglycan binding, lipid binding, and aminopeptidase activity. Removal of the N-glycans in Mucin-5B may result in a loss of CEVM's mechanical properties. The N-glycosites enriched in the apolipoprotein B β2 domain in CEVM were significantly changed, which may contribute to lipid composition modifications during storage. Moreover, N-glycosites in several metalloproteases were located within the functional domain or active site region, indicating that the decreased N-glycosylation levels may affect their structural stability, specific substrate binding, or enzyme activity. These findings provide novel insights into the roles of protein N-glycosylation during membrane weakening.

Quantitative Comparative Proteomic Analysis of Chicken Egg Vitelline Membrane Proteins during High-Temperature Storage

To explore the thermally induced alterations in chicken egg vitelline membrane (CEVM) protein abundances, a comparative proteomic analysis of CEVM after 10 days of storage at 30 °C was performed. Altogether, 981 proteins were identified, of which 124 protein abundances were decreased and 79 were increased. Bioinformatic analysis suggested that the altered proteins were related to structure (n = 10), mechanical properties (n = 13), chaperone (n = 15), antibacterial (n = 12), and antioxidant (n = 3). Alterations in abundances of structural proteins, possibly resulting from the disintegration of these complexes, were observed in this study, suggesting a loss in fibrous structure. Several proteins involved in mechanical strength (n = 10), elasticity (n = 3), and chaperone were decreased in abundances, which indicated that deficits in these proteins might affect the CEVM mechanical properties. These findings will extend our understanding of CEVM deterioration during high-temperature storage from a proteomic perspective.

Combination of super chilling and high carbon dioxide concentration techniques most effectively to preserve freshness of shell eggs during long-term storage

This study was made to examine the combined effects of stored temperature and carbon dioxide atmosphere on shell egg quality. The shell eggs were packed into polyethylene terephthalate/polyethylene (PET/PE) pouches and stored at 0 degrees C (super chilling), 10 degrees C, and 20 degrees C, respectively for 90 d. The atmospheric carbon dioxide concentration was controlled to obtain the 3 concentration levels of high (about 2.0%), medium (about 0.5%), and low (below 0.01%). Changes in Haugh unit (HU) values, weakening of vitelline membranes, and generation of volatiles were analyzed to evaluate the freshness of shell eggs. Results showed that, compared with the other combinations, the technique of super chilling and high carbon dioxide concentration enabled shell eggs to be most effectively stored for 90 d, based on estimations of the statistical significances of differences in HU values, and on maintaining the initial HU values during storage. In addition, the storage of shell eggs using this combination technique was found to significantly prevent the weakening of the vitelline membrane based on the estimations of numbers of eggs without vitelline membrane breakage when eggs broke, and significantly lowered the incidence of hexanal in the yolk from exposure to the gas chromatographic-mass spectrometric analyses of volatiles. Thus, these results confirmed that the combination of super chilling and high carbon dioxide concentration was the most effective technique for preserving shell eggs during a long term of 90 d compared with other combination techniques.

Comparison of quality attributes of shell eggs subjected to directional microwave technology

Microwaves have been shown to cause thermal as well as nonthermal destruction of pathogens such as Salmonella, which can be found in shell eggs. The objective of this study was to determine if using microwave technology would cause detrimental quality effects in shell eggs. Treatments included control (no treatment) and microwave-treated (20 s) shell eggs. There were no differences in mineral content, fatty acid profile, Haugh units, broken-out score, yolk index, emulsion stability, pH of whole egg, and foaming capacity between 2 treatments (P >or= 0.05). At 0 and 30 d, there were no noticeable differences in H(2)O activity between 2 treatments. The foaming stability and albumen thermocoagulation of microwave-treated eggs were significantly higher than control eggs (P <or= 0.05). The control eggs had significantly higher emulsion capacity and lower vitelline membrane strength than the microwave-treated eggs (P <or= 0.05). Poached eggs were evaluated by sensory testing for hardness, yolk color, and albumen color, and there are no noticeable differences at 0, 15, or 30 d. At 0 d, the color of control albumen was more yellow than the microwave-treated albumen, and the chalazae of the microwave-treated eggs was more attached than the control eggs (P <or= 0.05). The TBA reactive substances were similar for 2 treatments at 0, 15, and 30 d. Peroxide values were significantly higher in the microwave-treated eggs at d 0 (P <or= 0.05), but at 15 and 30 d, no prominent differences in peroxide values were noted (P >or= 0.05). Therefore, microwave technology can be applied to shell eggs without causing detrimental effects to quality.

Effects of extended storage on egg quality factors

Eggs were collected from a single inline processing facility weekly for 3 wk (replicates). The eggs were stored at 4 degrees C and 80% RH. Sampling began the day after collection and continued each week for 10 wk. During analysis, 24 eggs were examined for egg weight, albumen height, Haugh units (HU), shell strength, and vitelline membrane strength for each replicate. Egg weight decreased (P < 0.0001) from approximately 61 to 57 g after 10 wk of storage. Eggs from the second replicate were significantly (P < 0.0001) heavier than the other replicates by an average of 3 g. On average, albumen height decreased with extended storage (P < 0.0001) from 7.05 to 4.85 mm. Albumen height was approximately 0.2 mm higher for the eggs in replicate 2 compared with the other replicates (P < 0.01). Haugh unit values decreased during cold storage from 82.59 to 67.43 (P < 0.0001). There were no differences between replicates for HU values. No differences were detected for shell strength between replicates or during extended storage. A significant difference (P < 0.05) was found in detectable vitelline membrane strength between replicates, but this difference was less than 0.05 g. The elasticity of the vitelline membrane decreased during storage (P < 0.01) remaining low after 6 wk. Extended cold storage led to decreases in egg weight, albumen height, and HU. However, average HU values were still within the range for grade A. Shell strength was not affected by extended storage. Vitelline membrane elasticity also decreased, which could lead to yolks more easily rupturing as consumers crack the eggs. The results indicated that although the physical quality factors monitored in this study decreased during storage, egg quality was still acceptable beyond current recommended shelf life guidelines.

Effects of cryogenic cooling of shell eggs on egg quality

This study was conducted to investigate the effects of cryogenic cooling on shell egg quality. Gaseous nitrogen (GN), liquid nitrogen (LN), and gaseous carbon dioxide (GC) were utilized to rapidly cool eggs in a commercial egg processing facility and were compared to traditional cooling (TC). A modified food freezer was attached to existing egg processing equipment in order to expose eggs to the selected cryogen. In Experiment 1, eggs were treated with GN, LN, and TC then stored and tested over 10 wk. Experiment 2 eggs were treated (GC and TC) and evaluated for 12 wk. Quality factors that were measured included Haugh units, vitelline membrane strength and deformation at rupture, and USDA shell egg grades for quality defects. Haugh unit values were greater for cryogenically treated eggs as compared to traditionally cooled eggs (Experiment 1: 73.27, GN; 72.03, LN; and 71.4, TC and Experiment 2: 74.42, GC and 70.18, TC). The percentage of loss eggs in the GN treatment was significantly (P < 0.01) greater than those of the LN and TC treatments. Vitelline membrane strength was greater for the cryogenically cooled eggs versus traditional processing. Vitelline membrane breaking strength decreased over storage time. Vitelline membrane deformation at rupture was significantly (P < 0.05) greater for the cryogenically cooled eggs compared to the traditional eggs in each experiment. Use of the technology could allow for egg quality to be maintained for a longer time, which could increase international markets and potentially lead to extended shelf lives.