Functional aspects of blood plasma proteins.

The viscosity of solutions (6% w/w protein in 45% sucrose) of porcine and bovine whole blood plasma, porcine serum and porcine plasma fractions exhibited Newtonian behaviour between 20°C and 73°C. On further heating, the viscosity of these solutions increased exponentially producing a reversible gel structure at 76°C and an irreversible gel at 79°C. In contrast, egg albumen protein solutions indicated a relatively low initial viscosity but started to thicken at 65°C, forming reversible gels at 73°C and irreversible gels at 76°C. The viscosity of the egg albumen protein solutions was similar to that of the serum proteins and plasma protein fractions and less than that of whole plasma protein solutions. Viscosities lower than expected were exhibited by mixtures of whole porcine or bovine plasma and egg albumen proteins. However, synergistic interaction between the proteins of egg albumen and porcine plasma fraction I and fraction III (albumin) and porcine serum occurred at high temperatures of heating.     

Separation and identification of hen egg protein isoforms using SDS–PAGE and 2D gel electrophoresis with MALDI-TOF mass spectrometry

Knowledge of the chemical composition and physicochemical properties of native egg white and yolk is necessary to interpret the functional and biological properties attributed to specific egg components. To date, many of the proteins located in this complex biological fluid remain uncharacterised, if not unknown. High-resolution techniques for proteome analysis, including SDS–PAGE and 2-dimensional (2D) gel electrophoresis, combined with mass spectrometry, were employed to separate and identify several protein components in hen’s egg. An advanced and sensitive glycoprotein staining kit was used to detect the presence of glycosylated proteins in the egg samples. Numerous spots were revealed when a mixture of egg white and yolk was subjected to 2D gel electrophoresis. Several of the already known egg proteins were identified. Isoforms of ovalbumin and conalbumin were visualised. The presence of FLJ 10305 and Fatso proteins in the proteome of Gallus domesticus was also confirmed.     

Functional aspects of blood plasma proteins 4. Elucidation of the mechanism of gelation of plasma and egg albumen proteins

The mechanism of gelation of plasma and egg albumen proteins in a cake-type model system was elucidated by chemical modification, polyacrylamide gel electrophoresis and electron microscopy. It was demonstrated by chemical modification that gelation via disulphide bonds was predominant in all the plasma and egg albumen proteins. Hydrophobic and hydrogen bonds also prevailed in the plasma protein gels. In contrast the breakdown of hydrophobic and hydrogen bonds increased the strength of egg albumen gels. Electrophoretic characterization confirmed that most of the component proteins of plasma and egg albumen were modified chemically. Electron micrographs of the gels of plasma, egg albumen and a mixture of these proteins revealed a generally similar type of network structure, and indicated the compatibility of these proteins. The plasma gels had a more dense network, however, than the egg albumen gels and this was reflected in their correspondingly greater gel strength.     

冷冻储存对鸡蛋理化性质及微观结构的影响

本文通过测定pH、粘度、回弹高度和结构的变化,表征了置于-20 ℃下,储存不同的时间的新鲜鸡蛋的全蛋、蛋清、蛋黄、熟蛋及熟蛋黄的性质变化。实验结果表明：在-20 ℃下,新鲜鸡蛋随储存时间的增加,煮熟的全蛋回弹高度变小,熟蛋黄的回弹高度增大,从5 h到36 h,熟蛋黄的回弹高度从提高了2倍到4倍;蛋黄、蛋清和全蛋的pH值和粘度均发生了明显的变化,且pH的变化在储存10 h后更为显著;储存10 h的蛋清、蛋黄结构开始发生变化,蛋黄在冷冻24 h后质地变得较为平滑、紧密,可清楚表现为形成凝胶,到冷冻36 h后达到不可逆的变化。因此：在-20 ℃下,储存10 h,新鲜鸡蛋的品质已经由合格品下降为不合格的次品。     

Physicochemical and functional properties of Chinese soft-shell turtle (Pelodiscus sinensis) egg

The physicochemical properties of Chinese soft-shell turtle egg were characterized for functional use in the food industry. The egg yolk of un-fertilized soft-shell turtle eggs was separated and fractionated into granules and plasma. Then, the egg yolk, albumen, granules, and plasma were freeze-dried for further analysis. Results showed that the Chinese soft-shell turtle egg typically comprised 50% egg yolk, 34% albumen, and 16% shell in average. The egg yolk composed of 61% granules and 39% plasma. The granules contained most of the protein, while the plasma contained most of the lipid in egg yolk. The albumen contained about 26% ash on a dry weight basis. Lysozyme was the major component in turtle egg albumen. The protein solubility of egg yolk, granules, and plasma was affected by the changes in pH, while that of albumen remains constant. The emulsifying and foaming properties increased when the concentration increased for all samples. Both the yolk and the albumen in turtle egg exhibited better functional properties than those in normal hen egg. These physicochemical and functional properties of Chinese soft-shell turtle egg are fundamental and essential for future study and food applications.     

Protein Components Precipitated from Egg White by Removal of Salt

A precipitate that formed in egg white at low ionic strength affected the transparency of heat-induced gels prepared at pH 2-4 and low ionic strength. The precipitate solubilized with SDS solution containing 2-mercaptoethanol and urea included major proteins of the egg white, as shown by SDS-polyacrylamide gel electrophoresis. The bands of ovalbumin, conalbumin and other protein were smaller when the precipitate was washed with water, but lysozyme and ovomacroglobulin probably remained in the precipitate fraction. It seemed that ovalbumin, conalbumin, and other proteins co-precipitated with these two kinds of proteins. Lysozyme added to the supernatant of egg white after dialysis, did not appear to produce turbidity upon heating at pH 2.5, but whole egg white was converted to a turbid gel upon being heated at this pH.     

Multiplication and motility of Salmonella enterica serovars enteritidis, infantis, and montevideo in in vitro contamination models of eggs

The invasive ability of Salmonella enterica serovars Enteritidis, Infantis, and Montevideo in eggs was examined. Strains of these serovars originating from egg contents, laying chicken houses, and human patients were experimentally inoculated (0.1-ml dose containing 78 to 178 cells) onto the vitelline membrane of eggs collected from specific-pathogen-free chickens and incubated at 25 degrees C. The test strains were detected in 25 of 138 yolk contents by day 6, indicating the penetration of Salmonella organisms through the vitelline membrane. There were no significant differences in overall rates of penetration between serovars. The organisms were also detected in the albumen from 125 of 138 eggs tested by day 6. Growth to more than 10(6) CFU/ml was observed in 48 of the 125 albumen samples. An inoculum of 1000 Salmonella cells was added to 15 ml of albumen at the edge of a petri plate. A 10-mm-diameter cylindrical well, the bottom of which was sealed with a polycarbonate membrane with 3.0-microm pores, was filled with egg yolk and placed into the albumen at the center of the dish, which was maintained at 25 degrees C. Experiments were performed in triplicate with each strain. Salmonella organisms in all the albumen samples were detected by day 11. However, motility of the organisms toward the yolk was observed in only two dishes inoculated with the Salmonella Enteritidis strain from a human patient and in one dish inoculated with the Salmonella Infantis strain from liquid egg. The albumen samples obtained from the dishes inoculated with the Salmonella Enteritidis strain had high numbers of bacteria (>10(8) CFU/ml). The present study suggests that Salmonella organisms in egg albumen are unlikely to actively move toward the yolk, although depositionon or near the vitelline membrane can be advantageous for proliferation.     

Comparative proteomic analysis of chicken,duck, and quail egg yolks

A comparative analysis of egg yolk proteome of three major poultry species, namely, chicken, duck, and quail, was carried out with two-dimensional (2D) gel electrophoresis patterns and matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry. Proteins identified from these three poultry species shared high degrees of sequence and structure homology, which might be related to the bird’s adaptability under different environmental stresses. Few specific proteins were found in this study. Comparative 2D gel electrophoresis patterns of chicken, duck, and quail revealed that some protein-specific regions on gels could be used for authentic identification of poultry eggs. These findings could provide a fundamental understanding of different poultry egg protein profiles and showed us some new sights in egg yolk nutrients related to certain properties and functions.     

GROWTH, SURVIVAL AND HEAT RESISTANCE OF SALMONELLA TYPHIMURIUM AND ESCHERICHIA COLI IN REGULAR AND OMEGA-3 HENS EGG PRODUCTS

Omega‐3 enriched eggs are currently produced by hens fed a flax diet. Since omega‐3 polyunsaturatedfatty acids are prone to oxidation, the addition of vitamin E is supplemented into the hen's diet as an antioxidant. Typically these eggs contain about 2 and 4 times more omega‐3 fatty acids and vitamin E, respectively compared to regular eggs. Since table eggs have a long history of association with foodborne salmonellosis, it was of interest to compare the growth and/or survival of several bacterial pathogens in omega‐3 and regular eggs. In this respect nalidixic‐resistant Escherichia coli and Salmonella Typhimurium were inoculated into regular and omega‐3 hen's egg products (whole eggs, albumen, yolk) and incubated at 22, 8 and ?20C. Time‐course studies indicated that by 72 h both Salmonella and E. coli levels increased by 7 logs at 22C in both types of whole egg. At 8C population levels for these bacteria both increased by approximately 3 logs at 6 weeks. In regular and omega‐3 yolks, salmonellae maintained at 22 and 8C for 48 h and 6 weeks increased by approximately 6 and 1.5 logs, respectively. E. coli levels were higher in egg yolk compared to Salmonella at both temperatures. Regardless of the yolk source, however, no significant (P > 0.05) differences in population levels were observed. Survival patterns of E. coli at ?20C were not significantly (P > 0.05) different between whole egg sources. This trend was also observed in the yolks. For Salmonella no significant (P > 0.05) differences in survival were observed between yolk preparations maintained at ?20C. Increasing the level of α‐tocopherol from c. 63 to 240 ppm in regular egg yolk, resulted in no significant (P > 0.05) differences in the growth of Salmonella at 22C. In addition, when the bacterium was heated in regular egg yolk amended with vitamin E at 56.5C, no significant (P > 0.05) difference was observed in resistance regardless of α‐tocopherol (55‐713 ppm) or total tochopherol (92–1238 ppm) level.     

Effect of pH and of Succinylation on the Water Retention Properties of Coagulated, Frozen and Thawed Egg Albumen

Egg albumen was modified to improve water retention properties of the coagulated, frozen and thawed product. Albumen was found to contribute more to expressible moisture (%EM) of coagulated whole egg mixture than yolk. For frozen and nonfrozen treatments, albumen (pH gt; 9.5) reduced %EM in both the coagulated albumen and whole egg mixtures made with pH-adjusted albumen. Succinylated albumen (≤0.2% g anhydridelg albumen) reduced %EM for frozen and nonfrozen treatments. Albumen at pH 10.5 and 11.0 required less time to attain an equivalent cook value than at pH 7.0,8.0,9.0, and 10.0.     

Determination of 14C residue in eggs of laying hens administered orally with [14C] sulfaquinoxaline

Ten layer hens were dosed for 5 consecutive days with 6.2 mg kg^-1 [¹⁴C] sulfaquinoxaline (SQX). Eggs were collected from the hens during the 5-day dosing period and during a 10-day post-dose withdrawal period. Egg yolk and albumen were separated and assayed for total radioactive residues (TRR) using a combustion oxidizer and liquid scintillation counting techniques. Significant amounts of radioactivity were detected on the second day of dosing (greater than 24 h after the initial dose) in both egg yolk and albumen. First eggs were collected about 8 h after dosing; the second-day eggs were collected during 8-h period after the second dose. Radioactive residues reached a maximum on the fifth day of dosing in albumen, whereas on the second day of withdrawal in egg yolk, the peak TRR levels in albumen were about threefold higher than in yolk. Thereafter, the TRR levels declined rapidly in albumen and were detectable up to withdrawal day 6, whereas the TRR levels in egg yolk declined more slowly and were detectable up to withdrawal day 10. High-performance liquid chromatography analysis indicated that the parent drug sulfaquinoxaline was the major component in both the egg albumen and yolk. Additionally, this work suggests that egg yolk is the appropriate matrix for monitoring SQX residues     

Effect of Chemical Modifications on Some Physicochemical Properties and Heat Coagulation of Egg Albumen

Egg albumen was modified with succinic anhydride and a water-soluble carbodiimide, 1-ethyl-3(3-dimethylaminopropyl) carbodiimide. The chemically modified proteins exhibited only minor conformational changes, but were altered in their responses to heat treatment. Heat-induced coagulation was retarded by both modifications suggesting that thermocoagulation requires a balanced electrostatic attraction between protein molecules. Hydrophobicity measurements and pH-titration data suggest the involvement of hydrophobic and ionic interactions in heat aggregation and gelation of egg white proteins. The soluble fraction of the heat-coagulated proteins contained mainly monomers, while under conditions where a gel or coagulum was not formed, the heat-treated egg albumen solutions contained high M.W. soluble aggregates. A scheme for the thermal coagulation of egg albumen is proposed.     

Determination and depletion of amoxicillin residues in eggs

Eggs were used to study the determination and depletion of amoxicillin (AMO) residues after oral dosing hens (25.0 mg kg^–1, 50.0 mg kg^–1 body weight), once daily for five days. A reverse-phase high-performance liquid chromatography with fluorescence detection (RP-HPLC-FLD) method was developed to determine AMO residues in albumen, yolk and whole egg. By using pre-column derivatisation, an improved liquid–liquid extraction procedure was developed for sample preparation. AMO were extracted from eggs with acetonitrile. The extract solution was extracted using saturated methylene chloride. The supernatant was reacted with salicylaldehyde under acidic and heating conditions. Limits of detection (LODs) were 1.2 ng g^–1 and limits of quantification (LOQs) were 3.9 ng g^–1 for AMO. Recoveries of AMO from samples fortified at levels of 5.0–125.0 ng g^–1 ranged from 79.1% to 88.5% in albumen, 78.6–83.6% in yolk and 78.3–85.1% in whole egg, with coefficients of variation of ≤7.3%. The maximum concentrations of AMO in albumen, yolk and whole egg were found to occur at 1.5, 2.5, 1.5 days after withdrawal of medication respectively. AMO was not detectable in albumen at 7.5 days after final administration of AMO, at 10.5–11.5 days in yolk and 10.5 days in whole egg after administration of two oral doses. The method was applied during the residue study of AMO in order to formulate a reasonable withdrawal period to ensure food safety.     

Rheological Properties of Two Heat-Induced Protein Gels

Rheological properties of heat-induced gels from egg albumen and bovine plasma proteins were measured using a mechanical loading device. Each protein was tested at 8% protein concentration and heated for 0–120 min at 80°C in an agitating water bath. After heating, the viscosity index, apparent elasticity and initial penetration force of the gels were evaluated. Bovine plasma protein dispersions exhibited a substantially higher viscosity index, apparent elasticity and initial penetration force than egg albumen gels. Bovine plasma proteins produced a gel structure which was strong and elastic. By comparison, heat-induced gels of egg albumen proteins were fragile and somewhat brittle.     

鸡蛋中卵黄高磷蛋白的提取

建立了一种简单且适合于批量提取鸡蛋中的卵黄高磷蛋白的方法．先分离出其它水溶性蛋白质,再将沉淀物脱去脂肪,然后用１０％的ＮａＣｌ溶液（ｐＨ７．０）从所得的颗粒中提取卵黄高磷蛋白．每１００ｇ蛋黄提取１ｇ卵黄高磷蛋白粗制品,含氮１１．２２％,含磷７．７％,氮磷含量比值３．６４．卵黄高磷蛋白在ＳｅｐｈａｃｒｙｌＳ－２００图谱上有两个主峰,分别是α－ＰＶ和β－ＰＶ,相对分子质量为１６００００和１９００００．在聚丙烯酰胺凝胶电泳上出现相对应的两条谱带．经ＳＤＳ－聚丙烯酰胺凝胶电泳后,则出现相对分子质量从１０４～９×１０４左右的多条谱带,预示卵黄高磷蛋白是由多亚基组成的     

Effect of infectious bronchitis on the structure and composition of egg albumen

In an experimental flock of fowls infectious bronchitis produced reductions in the weights of the whole egg, albumen and shell and a decrease in the ratio of thick + inner thin albumen to outer thin albumen giving the whole albumen a watery appearance. In the thick fraction there was an increase in the water content and a decrease in the concentration of proteins including ovomucin and lysozyme which are believed to combine by electrostatic attraction to form the structural matrix. A reduction in ovomucin concentration was also detected in the outer thin fraction. The deficiency of this protein in the whole albumen was particularly marked and was probably mainly responsible for its abnormal appearance. A reduction in the percentage of ovalbumin I in the albumen proteins occurred in both the thick and the outer thin fractions and in the latter was accompanied by an increase in ovalbumin II. The only other significant changes found in this fraction were increases in the concentrations of sodium and potassium. The estimation of diffusible hexoses and hexosamines provided no evidence that hydrolysis of glycoproteins had occurred. From these and histological findings it was concluded that infectious bronchitis impairs the synthesis of albumen proteins by the magnum.     

日粮中添加不同油脂对鸡蛋工艺特性及质构指标的影响

摘 要：目的 本试验旨在探究蛋鸡饲粮添加不同油脂后对鸡蛋起泡性、乳化性、凝胶特性及蛋黄TPA、剪切力及蛋黄膜强度的影响。方法 在玉米-豆粕型基础日粮的基础上,分别添加1.5％豆油、1.5％猪油、1.5％混合油脂。结果 试验结果表明：与对照组相比,添加1.5％的猪油和混合油脂会不同程度的降低鸡蛋的工艺特性,显著增加蛋黄的硬度、咀嚼性;而1.5％豆油对鸡蛋的工艺特性及质构指标不会造成不良影响。结论 因此,为了满足蛋鸡生长能量需求及蛋品功能特性,建议在日粮中添加1.5％豆油。     

A STUDY OF TURKEY EGG YOLK 1. COMPOSITION AND ELECTROPHORETIC SEPARATION OF COMPONENTS1

Yolks from fresh eggs produced by Broad Breasted White turkeys were blended and analyzed. Proximate composition was determined and components were separated in 7% polyacrylamide gel. Turkey egg yolk was compared with chicken egg yolk. Turkey egg yolk contained a higher percentage of solids, fat, and protein than chicken egg yolk. When separated electrophoretically, components of chicken egg yolk migrated faster than those in turkey egg yolk. Turkey yolks could be resolved into 10 or 11 distinct components; chicken yolk, into 11 or 12 components, depending on electrophoretic technique.     

Uracil as a Potentially Useful Indicator of Spoilage in Egg Products

The relationship between sensory acceptability of egg products and their uracil content was investigated. Pasteurized liquid whole egg, albumen, and yolk were allowed to deteriorate for 5-8 days at temperatures not exceeding 22°C. Periodically a panel of USDA inspectors evaluated the products'odors and samples were frozen for analysis. Uracil and uridine were determined by high performance liquid chromatography. Uridine contents decreased and uracil contents increased as the products deteriorated. Spoilage odors were detected only in products containing ≥1.7 μ, g/g uracil. Analysis for uracil is potentially useful for objectively detecting egg decomposition.     

Influence of pH-Induced Unfolding and Refolding of Egg Albumen on Its Foaming Properties

ABSTRACT: The foaming properties of egg albumen, which had been subjected to low and high pH unfolding followed by refolding, were investigated. The foaming capacity of egg albumen, the stability of the foam, or both, could be improved by an unfolding and refolding regime by choosing proper unfolding and refolding pH values. The foaming capacities of egg albumen were greatly improved when the refolding was at pH 6.5, 7.5, or 8.5, whereas the foaming capacities could be either slightly increased or decreased when the refolding was at pH 4.5 or 5.5 compared with the controls. The foam stability was in almost all cases improved by the unfolding and refolding treatments except for a few cases of unfolding at pH 1.5 or 10.5. The foam stability and liquid drainage were improved most when the unfolding was at pH 12.5. Analysis of total and surface sulfhydryl groups, surface hydrophobicity, and protein analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) provided strong evidence that the partial unfolding of egg albumen proteins as well as the interactions among egg albumen proteins through disulfide and/or hydrophobic groups dictated the improvements in foaming properties. The increase in surface hydrophobicity showed better correlation with the improvement of foaming properties than the change of surface sulfhydryl content did.