Bioactivities of hen's egg yolk phosvitin and its functional phosphopeptides in food industry and health

Phosvitin, one of the most noteworthy bioactive components of hen egg yolk, is an amphiphilic protein that stands out with its unique composition and functionality in the food industry and health. Phosvitin consists of 4% of egg yolk dry matter and 11% of egg yolk proteins. It is considered as the most phosphorylated protein with 10% phosphorus. Besides, some potential novel phosphopeptides containing clusters of phosphoserines can be derived from hen's egg yolk phosvitin. Phosvitin, which has many functional features thanks to its unique structure, is known primarily for its metal bonds binding (iron, calcium, etc.) feature. On the other hand, its phosphopeptides may increase the bioavailability of metals compared to phosvitin. Although this feature of phosvitin may partially decrease the bioavailability of especially iron in the egg, it allows the phosvitin to have many bioactivities in the food industry and health. Lipid oxidation, which is a serious problem in the food industry, can be inhibited by adding phosvitin and its derived phosphopeptides to the food production chain via inhibiting bivalent iron. Because phosvitin is an amphiphilic protein capable of chelating, it also shows potential antibacterial effects against the Gram-negative bacteria. Moreover, the literature has recently been attempting to define the promising relationship between phosvitin and its phosphopeptides and plenty of health-promoting activities such as immune-enhancing, melanogenesis inhibitor, anti-ageing, and anticancer. In this review, current information on the hen's egg yolk phosvitin and its phosphopeptides and their bioactivities in the food industry and health are discussed and some future directions are given.     

Effect of pH and salt concentration on the solubility and density of egg yolk and plasma egg yolk

This work aimed to evaluate the solubility and density of egg yolk and plasma egg yolk in three types of salts (NaCl, Na₂SO₄ and (NH₄)₂SO₄) at different pH values (3.0, 4.03, 6.5, 8.7 and 10.0) and salt concentrations (0.05, 0.1, 0.2, 0.3 and 0.5 mol/l). Solubility data of both egg products showed a distinct behaviour for each type of salt. A 4th-order polynomial model fitted the solubility data with R² values higher than 0.83. It was observed the increase of the density as the salt concentration increase. The model used for density data correlation shown R² values higher than 0.94.     

Complex coacervates obtained from interaction egg yolk lipoprotein and polysaccharides

Protein–polysaccharide coacervates formation was evaluated under influence of pH (3.0, 4.0, 6.5, 8.5 and 10.0), temperature (10, 20, 30, 40 and 50 °C) and polysaccharide mass (0.025, 0.033 and 0.050 g). It was possible to observe that solutions with lower turbidity values were found in pH band 3.0 to 4.0. Statistical analysis of turbidity data have shown that for all polymers pH was meaningful in coacervate formation, although for some, besides pH, temperature and polymer concentration could also influence significantly (p < 0,05) in coacervate formation. Encapsulates morphology made by coacervation was directly linked to the kind of polymer used and its interactional degree. Dehydrated coacervates have presented heterogeneous morphology, different from their original structures.     

Variable effects on egg yolks and yolk lipoprotein fractions of feeding methyl sterculate to hens: Periodic changes in lipid composition and gelation temperature

As part of a study of the reasons for the large effects of a small dietary supplement of methyl sterculate on the physical properties and lipid composition of hen's egg yolk, individual yolks from sterculate-fed hens have been examined. These yolks set to a firm gel on cooling in the range 20-0 °C, but there were large variations in eggs from different hens that were accompanied by variations in the proportion of saturated fatty acid residues in the yolk lipids. Gel formation was reversible on immediate rewarming but prolonged storage at low temperature caused irreversible alterations. Diluted yolk showed analogous changes in viscosity on cooling and provided a convenient model system for examining the effect of pH, ionic strength, and the action of trypsin. From these results it is concluded that the protein of the high-lipid low-density lipoprotein of yolk is directly involved in the gelation of the yolk. A series of eggs laid by one sterculatefed hen over 30 days showed large and possibly periodic variations in the lipid composition and gelation temperature of the yolks. These results and some data from other hens suggested that large variations in yolk properties accompany a high response to sterculate feeding.     

Thermal behaviour of lyophilized egg yolk and egg yolk fractions

Despite its importance from a technical point of view, the influence of temperature on rheological behaviour of lyophilized egg yolk and egg yolk fractions has not yet been studied. In this work, the effect of temperature on rheological properties of these products have been analysed by means of stationary and oscillatory measurements. Firstly, the Arrhenius equation was employed to assess the influence of temperature on viscosity. In addition to temperature effect, solid content showed to be determinant on viscosity, while particle size, water holding capacity and wettability influence on rheological behaviour of samples were not critical. Secondly, rheological changes during heat-induced gelation of the samples were also investigated by means of dynamic tests and the critical network exponents at the gelation point were calculated. An analysis of variance (ANOVA) was also performed using the Statgraphics Plus to evaluate experimental data. Results show that proteins of egg yolk fractions possess a similar network structure before and after gelation, while egg yolk structure is clearly modified by gelation process. Composition and structure is the main responsible of differences between samples.     

Changes in rheological behaviour and functional properties of hen's egg yolk induced by processing and fermentation with phospholipases

Functional changes of hen's egg yolk rheological behaviour as a result of processing (pasteurisation, freeze-drying) and modifying its phospholipids using phospholipase A₁ (PLA₁) and phospholipase A₂ (PLA₂) were studied. It could be shown how fermentation with phospholipases affects the different steps of heat-induced gelation of egg yolk. As a consequence of fermentation of native yolk with 0.1% PLA₁, the first viscosity maximum was shifted from 79 to 97 °C. In fermented pasteurised yolk, the homogenous gel-like consistency from the first viscosity maximum was even stabilised up to 100 °C. The second viscosity ascent, which indicates solid gel structures (caused by aggregation of denatured proteins), was prevented entirely. In contrast to pancreatic PLA₂, fermentation of egg yolk with microbial PLA₁ resulted in a hydrolysis of approximately 78% of phosphatidylethanolamine and a significant change in flow behaviour (of yolk solutions).     

低温沉淀法提取高纯度蛋黄卵磷脂的工艺研究

以新鲜蛋黄液为主要原料,探讨了卵磷脂提取过程中料液比、己烷-丙酮体积比、冷冻温度对卵磷脂得率及磷脂含量的影响。结合单因素与正交实验分析,获得提取高纯蛋黄卵磷脂的最佳工艺条件:料液比1∶4.5（g/mL）,己烷-丙酮体积比1∶2.5,冷冻温度-20℃,此条件下卵磷脂得率为9.37%,磷脂含量为97.68%。经HPLC检测,结果表明:磷脂酰胆碱含量77.42%,磷脂酰乙醇胺含量18.47%,显示了较好的工业应用前景。      

卵黄高磷蛋白的研究进展

结合国内外关于卵黄高磷蛋白的最新研究动态,介绍了它的组成、提取、功能性质及其开发应用前景。卵黄高磷蛋白有着良好的热稳定性、抗氧化性及乳化性能,在一定条件下对大肠杆菌有致死作用,将之与半乳甘露聚糖连在一起,其功能性质有提高。卵黄高磷蛋白及其水解得到的磷酸肽类有很好的持钙性,这些生物活性肽能增加小肠对钙的吸收及其在体内的蓄积,也能促进铁、锌等离子的吸收,因此它作为潜在的功能食品因子将有良好的应用前景。     

Effect of ageing on different egg yolk fractions on surface properties at the air–water interface

The aim of this study was to evaluate the impact of egg ageing on the surface properties of whole and fractionated yolk at the air–water interface. Eggs were stored at 4°C for 24 h, 1 week and 3 weeks after laying. A laboratory scale fractionation process was then applied at each ageing time. Egg yolk was separated into two fractions, plasma composed of low‐density lipoproteins (LDLs) and livetins, and granules formed by high‐density lipoproteins (HDLs), phosvitins and LDLg (g = granule). Moreover, recombined plasma and granules fractions were investigated to highlight a potential synergic effect on surface properties. Results have shown the main contribution of LDLs on surface properties of yolk and an improvement of granules surface properties when they are disrupted. Moreover, ageing affected surface properties differently depending on the considered fractions. Broken LDLs and disrupted granules could explain this observed behaviour. Recombined fractions showed different compression isotherms at the air–water interface than whole yolk.     

蛋黄卵磷脂冲剂的研制

卵磷脂是一种重要的生理活性物质,鸡蛋卵黄中含有丰富的卵磷脂,且磷脂配比优良,本试验以蛋黄粉为原料,用乙醇溶剂提取法提取蛋黄卵磷脂,采用优化的配方研制出口感良好并具保健功能的蛋黄卵磷脂冲剂,并对工艺条件进行探讨,为蛋品的综合利用探索新的途径。     

Carbohydrates of the chicken egg yolk

In the yolk of the eggs of hens receiving traditional feeding hydrocarbon mixtures contained in trace amounts therein were analyzed by a specially elaborated method. For identification and quantification the data of the gas liquid chromatography, chromato-mass-spectrometry and ultraviolet spectrophometry were used. In a complex hydrocarbon mixture chromato-mass-spectrometry helped identify the alkanes of the normal and isoprenoid structure, cycloalkanes, of terpene and sterene types. The alkanes and cycloalkanes fraction content was found to comprise 15-30 per 1 mg of the raw mass of the yolk, of the p-alkanes--1-3 mg, squalene--15-17 mg and of monocyclic arenes--about 1 mg.     

咸蛋黄香肠的研制

探讨了咸蛋黄香肠的生产工艺和配方,采用正交实验设计确定的最佳配方为白酒3％、白胡椒0.2％、淀粉7％、食盐3％、食醋3％,制作出的香肠风味独特,组织状态良好,口感细腻.     

Analysis of glycerophosphonolipids in egg yolk

Glycerophosphonolipids are a relatively unknown class of polar lipids. Little information is available on any special biological function of these substances or specific technological use for them. Since glycerophosphonolipids have been reported to occur in egg yolk, further studies are needed in order to determine their relevancy. However, analysis of these lipids is rather difficult, due both to their chemical similarity to phospholipids and the lack of commercially available reference substances. Therefore, a reference substance for phosphono analogues of phosphatidylethanolamine (PnE)—1,2-dioctadecanoyl-glycero-3-aminoethylphosphonate—has been synthesized and an HPLC/ELSD method to separate PnE from its phosphonoanalog was developed. Although the present results showed no evidence of glycerophosphonolipids in egg yolk (limit of detection <0.02% for PnE), the spectroscopic data gathered here do point to an approach for further analysis of glycerophosphonolipids. Furthermore, a characteristic ESI–MS² fragmentation pattern for PnE was established, which can be used as a “fingerprint” for the identification of this substance in other biological systems. It was found to be characteristic for a fatty acid fragment to be split off as an internal anhydride (ketene) [M–H–RCH=C=O]⁻ along with the whole fatty acid fragment [M–H–RCH₂COOH]⁻ in the negative ion mode. In the positive mode, there was a selective loss of only the head group of the phosphonolipid [PO₃H₂–C₂H₄–NH₃]⁺, resulting in the so-called “diacylglycerol-like fragment ion” [DAG]⁺.     

Lipid‐lowering mechanism of egg yolk in normal rats

The ingestion of egg has been reported to lower blood cholesterol, but the mechanism is unclear. Here, the biochemical metabolic mechanism by which the oral administration of egg yolk affects blood lipid reduction was investigated using normal rats. Blood triglycerides and total cholesterol were lower and high‐density lipoprotein cholesterol was higher in an egg yolk‐given group compared to other groups, while low‐density lipoprotein cholesterol was increased in the pork belly oil‐given group. HMG‐CoA reductase activity was higher in the pork belly oil‐given group, compared to an egg yolk‐given group, a weekly alternating administration of pork belly oil and egg yolk‐given group, and the saline‐given normal control group. However, faecal excretions of total sterol, neutral sterol and acid sterol in an egg yolk‐given group were higher compared to the pork belly oil‐given group, a weekly alternating administration of pork belly oil and egg yolk‐given group, and a normal control group. The results suggested that ingestion of egg decreased blood lipids.     

Comparison of extraction conditions for milk and hen's egg allergens

The evaluation of recovery rates by extracting milk powder and egg powder using eleven different extractants gave approximately similar results for both foods. Compared with the other extraction solutions investigated, ‘1% Tween 20® and 0.4% Triton X-100®’ and ‘4% SDS’ are the most suitable extractants to isolate proteins of hen's egg or milk. When comparing calculated protein recovery rates of egg and milk powder extracts, the results clearly indicated that the choice of a suitable extractant is of particular importance. Qualitative investigation of the extracts via LDS-PAGE followed by silver staining as well as immunoblotting confirmed the results of protein quantification. Hence, the immunoblots showed that the extraction agents had no negative influence on the antigenicity of the extracted allergenic proteins. In this study, variation of extraction temperature led neither to any benefit in extraction quality nor to degradation. Changing pH did not reveal any trends, but progressive protein hydrolysis under strong alkaline conditions. Evaluation of recovery rates as well as results of unspecific and specific staining of the extracts showed that an extraction time of 1?h is sufficient for an appropriate sample preparation. For investigations with and without food matrix different results were obtained. In summary, wheat starch did not influence the extraction quality within all examined materials and different extractants. In contrast, using fat powder and dry cake mix, respectively, led to different results in the extraction procedure. When fat powder and dry cake mix were used as food matrices, some protein recovery rates decreased and some increased depending on the allergen material. These results highlight the fact that the suitability of the extractant not only depends on the properties of the allergen but furthermore on the type of matrix containing the allergen.