Production of phospholipids from spray-dried egg yolk by consecutive in situ solid phase extraction with acetone and ethanol

Egg yolk lipids were extracted and fractionated into neutral lipids and phospholipids using acetone followed by ethanol as eluting solvents to a column consisting of spray-dried egg yolk. This technique, named in situ solid phase extraction, can be performed with spray-dried egg yolk due to the properties of this material. The effect of temperature, flowrate and scale has been studied. Results suggest that the methodology is suitable for industrial implementation.     

On hen egg fractionation: applications of liquid chromatography to the isolation and the purification of hen egg white and egg yolk proteins

Liquid chromatography has been used as a means of egg protein analysis or as a method for the purification of egg proteins. Several Chromatographic methods, including gel permeation, ion-exchange, reversed-phase, hydrophobic interaction, and immobilized-ligand-affinity chromatography, have been carried out for the separation or the purification of egg yolk or egg white proteins. Ion-exchange chromatography appears to be the most frequently used method for protein isolation and it is the easiest to adapt to a process scale. From an analytical point of view reversed-phase chromatography is, at the moment, the recommended method for egg white analysis. Egg white has been fractionated more often by liquid chromatography than has egg yolk. Several Chromatographic methods have been developed on a laboratory scale, but the application of these techniques on an industrial scale remains limited.     

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.     

Fatty acid and carotenoid composition of egg yolk as an effect of microalgae addition to feed formula for laying hens

Hens were fed five diets based on rapeseed/corn oils with or without addition of the marine microalgae, Nannochloropsis oculata. Colours of egg yolk, fatty acid profiles in phospholipid (PL) and triacylglycerol (TAG) fractions and carotenoid contents were analysed. The major effects on yolk fatty acid composition were observed in the PL fraction with changes in 18:2n − 6, 18:3n − 3, 20:4n − 6, 20:5n − 3 and 22:6n − 3. The highest amounts of eicosapentaenoic acid and docosahexaenoic acid were obtained from the diet containing 20% N. oculata, whereas the highest arachidonic acid content in yolk was from the corn oil diet. In addition, colour (a* value) and carotenoid content increased when N. oculata was included in the diet. Long chained fatty acids were almost exclusively present in the PL fraction of yolk. This study shows that fatty acid composition and carotenoid content of egg yolk are improved by addition of N. oculata in laying hen diet.     

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.     

Adsorption of egg yolk plasma cholesterol using a hydrophobic adsorbent

Data on hydrophobic adsorption equilibrium of egg yolk plasma cholesterol were obtained using Streamline Phenyl^® resin in batch suspension at room temperature (25 °C). Influence of two types of salt (NaCl and Na₂SO₄) at four concentrations (0.0; 0.05; 0.1, and 0.2 M) on equilibrium was analyzed. Increased salt concentration reduced the amount of cholesterol adsorbed in the resin. Two isotherm models (Langmuir and a modified model based on type S-isotherm) were used to represent solid-liquid equilibrium data. The latter led to a better fit of the equilibrium data, with a 99.8% value of RSSE. A 70% reduction of the cholesterol content in the plasma was obtained with a 1:4 plasma:water dilution ratio.     

注射用富含卵磷脂蛋黄磷脂制备研究

以脱脂蛋黄粉为原料,采用柱层析法制备供注射用富含卵磷脂蛋黄磷脂,对所得产品进行详细分析测试,其各项指标均符合我国药典质量标准,并与国外同类产品进行比较。     

Fatty acid composition of egg yolk phospholipid fractions following feed supplementation of Lohmann Brown hens with humic-fat preparations

The effect of feed supplementation with humic-fat preparations on the fatty acid composition of egg yolk phospholipid fractions was studied. The Lohmann Brown was the experimental hen strain and two feeding mixtures were applied – the standard feed and the mixture supplemented with humic-fat preparations. The fatty acid profile of yolk lipids was significantly affected (P = .05) by the supplementation of feed and total increase of n-3 polyunsaturated fatty acids (PUFA) was established. A different distribution of n-3 PUFA in egg yolk lipid fractions was observed: α-linolenic acid (18:3) was found in the triacylglycerol fraction, whereas docosahexaenoic acid (22:6) was detected in the phospholipid fractions. Supplementation of the hen’s diet with humic-fat preparations resulted in the production of n-3 enriched eggs with decreased n-6/n-3 ratio in all phospholipid fractions in comparison to the eggs from the control group.     

Physicochemical properties of leftover egg yolk after livetins removal

Isolation of immunoglobulin Y (IgY) from egg yolk using water-dilution method generates large quantities of leftover pellet as the co-product. Although egg yolk is well known for its great emulsion property, there is a lack of understanding on how livetins removal would affect the emulsion and rheological properties of the pellet. Therefore, the objective of this study was to determine the effect of soluble protein removal on emulsifying and rheological characteristics of the leftover egg yolk. Egg yolk pellet exhibited distinct structural and physicochemical properties after soluble protein removal. Emulsions prepared from pellet were more vulnerable to coalescence instability than that of egg yolk, although both had a similar oil droplet size. Egg yolk displayed a Newtonian behaviour, compared to a shear-thinning behaviour of pellet. Pellet showed a higher apparent viscosity as well as higher viscoelastic moduli than those of egg yolk, probably due to increased hydrogen bond and hydrophobic interactions in the pellet. Therefore, the changes on the emulsion stability and the rheological properties of egg yolk after soluble proteins removal should be considered in food formulation and processing. Further study is needed to improve the emulsion property of pellet for uses in the food industry.     

In situ solid phase extraction of lipids from spray-dried egg yolk by ethanol with subsequent removal of triacylglycerols by cold temperature crystallization

ln situ solid phase extraction of lipids from spray-dried egg yolk by ethanol combined with subsequent removal of triacylglycerols from the ethanolic extract by cold temperature crystallization is described. By this procedure a lipid product is obtained which contains 86 g/l00 g phospholipids, 4 g/l00 g triacylglycerols and 10 g/100 g cholesterol. About 80% of spray-dried egg yolk phospholipids are recovered in this product. The product may serve as a source of phospholipids for specialized dietetic applications due to their relative high contents of both n-3 and n-6 long-chain polyunsaturated fatty acids. The procedure which requires no mechanical extractor and filtering device is amenable to scale up since recovery is not affected by changes in column volume or flow rate. This suggests the possibility of profitable industrial exploitation.     

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.     

Ultrasonic-assisted enzymatic degradation of cholesterol in egg yolk

An ultrasonic-assisted enzymatic process was developed for effective degradation of cholesterol in natural egg yolk. The objective of this study was to follow the catalytic activity of cholesterol oxidase against egg yolk cholesterol in an effort to obtain a cholesterol reduced egg yolk without affecting the major nutrients composition of egg yolk. Cholesterol oxidase was used to catalyze the degradation of cholesterol in egg yolk. Firstly, a 30 g portion of the egg yolk was pretreated by ultrasonic for 15 min at 200 W and then incubated for 10 h with cholesterol oxidase concentration of 0.6 U/g egg yolk at 37 °C. Finally, the cholesterol level in egg yolk was reduced to 8.32% of its original concentration without affecting the quality attributes of the yolk.

Industrial relevance

With the increase of public awareness to the dangers of cholesterol in recent years, a large number of popular food products have drawn criticism for containing high levels of cholesterol. Many reduced cholesterol egg products have been developed for market requirement. The results indicate that the ultrasonic-assistant extraction is an effective method for effective degradation of cholesterol in natural egg yolk. The knowledge gained from this study should be useful for further exploitation and application of the resource. Cholesterol-reduced egg yolk promises to be a value-added functional food with all the health enhancing attributes associated with egg yolk.     

Influence of storing time and temperature on the viscosity of an egg yolk

The influence of storing time and temperature on rheological behavior of egg yolk was investigated. The eggs of two brown egg-laying breeds (Bar Plymouth Rock and Rhode Island Red) were stored for 1, 2, 3, 4, and 8 weeks at constant temperatures: 4 °C, 8 °C, 12 °C, and 16 °C. The apparent viscosity was measured by a rotational viscometer as a function of shear rate. It was found that yolk samples exhibited shear-thinning (pseudoplastic) behavior. The shear-thinning behavior was fitted well into Herschel–Bulkley model (with a satisfying correlation of R² > 0.95). For the selected shearing rate, viscosity was measured in relation to shearing time. The time-dependant viscosity decreased rapidly with time and, at lower share rates, reached an equilibrium state. The time-dependant viscosity was also found to decrease with storage time. The value of pH changed (increased) during storing. No clear dependence between pH value and viscosity was confirmed.     

蛋黄卵磷脂的分离纯化研究进展

该文介绍了卵磷脂的理化性质、生理功能,综述了国内外对蛋黄卵磷脂的分离提取和精制方法及其在食品中的应用等方面的研究进展,展示了其在食品、药品等研究开发方面的广阔前景。     

膜分离纯化蛋黄卵磷脂工艺研究

研究膜分离技术纯化蛋黄卵磷脂(PC)工艺,经实验,确定最终膜分离纯化工艺条件为：采用100nm→20 nm双膜法分离,温度25℃、溶剂为乙醇—正己烷(75/25)、膜压力0.1 Mpa、料液比1：20(w/v);在此条件下,所得膜分离制品磷脂酰胆碱(PC)纯度为85％。     

Influences of storage time and temperature on the xanthophyll content of freeze-dried egg yolk

The influences of storage time, temperature (−18 or +20 °C, both in the dark), and prior pasteurisation on the xanthophyll content of freeze-dried egg yolk were investigated. After six months of storage, the synthetic xanthophylls all-E-canthaxanthin and β-apo-8-carotenoic acid ethyl ester showed considerably higher stability (with losses of 19–34%) than did the natural pigments all-E-lutein and all-E-zeaxanthin (losses of 59–69%). At all stages of storage, the xanthophyll contents of unpasteurised and previously pasteurised samples did not differ significantly, and no obvious influence of storage temperature was observed. With respect to xanthophyll content, the results suggest that there is no necessity for low-temperature storage of freeze-dried egg yolk.     

蛋黄卵磷脂的提取工艺研究

介绍先用丙酮沉淀,再用乙醇与石油醚组成的二元混合溶剂萃取蛋黄卵磷脂的方法。对丙酮用量、丙酮pH值、乙醇与乙醇的比例及该二元混合溶剂用量4因素对卵磷脂提取率的影响进行研究。正交实验结果表明对10g蛋黄,丙酮用量为30mL、丙酮pH值为8、乙醇与石油醚的比例为3︰1且该二元混合溶剂用量为30mL时卵磷脂提取率最高。     

Rheological properties,stability and sensory evaluation of low-cholesterol mayonnaises prepared using egg yolk granules as emulsifying agent

No important practical applications have been developed for egg yolk granules until now. However, as they have low cholesterol content and maintain good emulsifying properties, granules could be employed as a potential ingredient in the food industry. In this work, granules obtained in the laboratory by a simple procedure were used as emulsifying agent in mayonnaise preparation. The aim was to develop a low-cholesterol mayonnaise with properties similar to those of typical mayonnaise. For this purpose, three low-cholesterol formulations prepared in the laboratory were compared with a mayonnaise prepared using yolk and also with a commercial mayonnaise. The rheological characteristics of mayonnaises were evaluated, as well as their microstructure and sensorial properties. In addition, colour and particle size measurements at different times of storage were carried out to assess stability. According to results, the use of granules allows the preparation of a low-cholesterol mayonnaise which shows similar characteristics to those of a typical mayonnaise.     

蛋黄卵磷脂中两种溶血磷脂的分离与结构鉴定

通过柱层析分离法对蛋黄卵磷脂中的两种溶血磷脂(溶血磷脂酰胆碱和溶血磷脂酰乙醇胺)进行分离纯化,并采用ESI质谱、核磁共振氢谱和碳谱、气相色谱对其进行结构鉴定。结果表明:蛋黄来源的溶血磷脂酰胆碱主要由1-棕榈酰溶血磷脂酰胆碱,1-亚油酰溶血磷脂酰胆碱,1-硬脂酰溶血磷脂酰胆碱,1-油酰溶血磷脂酰胆碱4种化合物组成;溶血磷脂酰乙醇胺主要由1-棕榈酰溶血磷脂酰乙醇胺,1-硬脂酰溶血磷脂酰乙醇胺,1-油酰溶血磷脂酰乙醇胺3种化合物组成。     

Rheological characterisation of salad-dressing-type emulsions stabilised by egg yolk/sucrose distearate blends

The overall objective of this work was to fully characterise the rheological behaviour of oil/water emulsions stabilised by egg yolk and a sucrose ester of intermediate hydrophilic-lipophilic balance. The influence of the egg yolk/sucrose ester weight ratio in the emulsifier blend was studied by keeping the total amount of emulsifier constant. With this aim, steady state and transient flow tests, oscillatory measurements within the linear viscoelasticity regime and stress relaxation tests were carried out. Rheological tests were complemented with droplet size measurements. The results demonstrate that the rheological response and droplet size of the emulsions studied clearly depend on the weight ratio of emulsifiers in the binary blends. Steady-state and transient viscosities, as well as the dynamic functions, significantly increase with sucrose distearate concentration in the emulsifier blend. However, the evolution of other rheological parameters related to shear-induced structural breakdown, such as the critical strain for the onset of the non-linear viscoelastic behaviour, the relative deviation of the Cox-Merz rule, the time corresponding to the stress overshoot in transient tests or the damping function indicates a more developed and resistant structural network at higher egg yolk concentrations in the emulsifier blend. These results were discussed on the basis of a gel-like continuous phase formed by the sucrose ester and the highly flocculated state favoured by egg yolk.