IgY isolation from a watery by-product obtained from an egg yolk fractionation process

The possibility of recovering IgY from a watery by-product produced during an egg yolk fractionation process was evaluated. The protocol employed for the extraction of IgY was the polyethylene glycol precipitation method. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was carried out to confirm the presence of IgY at the different steps of the IgY purification process. Finally, the amount of IgY obtained was quantified by means of anion exchange chromatography. Native egg yolk was employed as IgY reference source, and results showed that the by-product could be at least as suitable as egg yolk as an IgY source. Additionally, the use of the by-product as a source of biotechnological compounds, such as IgY, leads to an increase in the value added during the egg yolk fractionation process.     

Extraction of Phospholipids from Structured Dry Egg Yolk

Chicken egg yolk is a concentrated source of phospholipids (PL). Extracting egg PL with high efficiency is vital to the availability and economics of this high-valued lipid product. In this study, two types of structured dry egg yolk materials, yolk flakes and pellets, were prepared. Two commonly used solvents, hexane and ethanol, were tested on the extraction of total yolk lipids including the PL. The PL fraction was obtained by the conventional cold acetone precipitation. The drum-dried yolk flakes were shown to be an ideal starting material for total lipid and PL extraction. Anhydrous ethanol can extract almost all the neutral lipids and PL with little change to the individual components of the native PL. A PL product with a purity of more than 90 % and a yield of 99 % can be prepared using this method.     

Extraction of phospholipids from structured dry chicken egg

Chicken egg contains a high level of phospholipids (PL) in the yolk. Recovering yolk total lipids and extracting egg PL with efficiency are important to the availability and utilization of these health‐promoting lipid products. In this study, we prepared two structured dry egg yolk materials and used two common solvents to extract and concentrate the PL. We found that drum‐dried flake‐like yolk is an ideal starting material for lipid extraction. Anhydrous ethanol can extract almost all the neutral lipids and PL. PL with purity over 90% can be prepared by cold acetone precipitation from the total lipids.     

蛋黄磷脂的提纯

利用蛋白质不溶或微溶于某些溶剂的特点,用混合溶剂萃取粗蛋黄磷脂制备精蛋黄磷脂的工艺,该工艺易于实现工业化生产,磷脂纯度可达98%以上。     

The Effects of Biopolymer Encapsulation on Total Lipids and Cholesterol in Egg Yolk during in Vitro Human Digestion

The purpose of this study was to examine the effect of biopolymer encapsulation on the digestion of total lipids and cholesterol in egg yolk using an in vitro human digestion model. Egg yolks were encapsulated with 1% cellulose, pectin, or chitosan. The samples were then passed through an in vitro human digestion model that simulated the composition of mouth saliva, stomach acid, and the intestinal juice of the small intestine by using a dialysis tubing system. The change in digestion of total lipids was monitored by confocal fluorescence microscopy. The digestion rate of total lipids and cholesterol in all egg yolk samples dramatically increased after in vitro human digestion. The digestion rate of total lipids and cholesterol in egg yolks encapsulated with chitosan or pectin was reduced compared to the digestion rate of total lipids and cholesterol in other egg yolk samples. Egg yolks encapsulated with pectin or chitosan had lower free fatty acid content, and lipid oxidation values than samples without biopolymer encapsulation. Moreover, the lipase activity decreased, after in vitro digestion, in egg yolks encapsulated with biopolymers. These results improve our understanding of the effects of digestion on total lipids and cholesterol in egg yolk within the gastrointestinal tract.     

Selective extraction of phospholipids from egg yolk

Solubility differences of phospholipids and tri-glycerides in methanol have been used with advantage for the selective quantitative extraction of phospho-lipids, almost free of triglycerides, from egg yolk. Cholesterol, a comparatively minor component of egg yolk lipids, is easily removed from the methanolic solution of phospholipids by low temperature crystal-lization (5 C), if required.     

Novel method to administer radiolabeled lipid to juvenile oysters

Particles prepared from egg yolk were shown to encapsulate protein and to be in a size range that would be filtered by the oyster. A radiotracer study involving the addition of radiolabeled phosphatidylcholine to egg yolk demonstrated that the egg yolk particles were taken up and metabolized by juvenile oysters (Crassostrea gigas). Catabolism of the radiolabeled lipid and subsequent resynthesis into non-lipid components occurred to a slight extent. The main factor responsible for the distribution of radioactivity amongst the lipids in the stomach tissue was believed to be transacylation.     

Overexpression of G0/G1 Switch Gene 2 in Adipose Tissue of Transgenic Quail Inhibits Lipolysis Associated with Egg Laying

In avians, yolk synthesis is regulated by incorporation of portomicrons from the diet, transport of lipoproteins from the liver, and release of lipids from adipose tissue; however, the extent to which lipolysis in adipose tissue contributes to yolk synthesis and egg production has yet to be elucidated. G0/G1 switch gene 2 (G0S2) is known to bind and inhibit adipose triglyceride lipase (ATGL), the rate-limiting enzyme in lipolysis. The objective of this study was to determine whether overexpression of the G0S2 gene in adipose tissue could successfully inhibit endogenous ATGL activity associated with egg laying. Two independent lines of transgenic quail overexpressing G0S2 had delayed onset of egg production and reduced number of eggs over a six-week period compared to non-transgenic quail. Although no differences in measured parameters were observed at the pre-laying stage (5 weeks of age), G0S2 transgenic quail had significantly larger interclavicular fat pad weights and adipocyte sizes and lower NEFA concentrations in the serum at early (1 week after laying first egg) and active laying (5 weeks after laying first egg) stages. Overexpression of G0S2 inhibited lipolysis during early and active laying, which drastically shifted the balance towards a net accumulation of triacylglycerols and increased adipose tissue mass. Thereby, egg production was negatively affected as less triacylglycerols were catabolized to produce lipids for the yolk.     

Extraction of Phospholipids from Egg Yolk Flakes Using Aqueous Alcohols

Two alcohols, ethanol and butanol, with different water contents were evaluated for phospholipids (PL) sequential extraction from drum dried egg yolk flakes. It showed that butanol was more effective in extracting total yolk lipids compared to ethanol, but the PL in the extract had the same concentration as in the original yolk total lipid. The use of aqueous ethanol of 95 and 75% resulted in lipid extracts with higher PL concentration during the initial stages of the sequential extraction. When ethanol was further diluted to a concentration of 55%, the solvent lost its PL extraction ability, and the total lipid recovery also decreased dramatically. When both the PL purity and recovery were considered, 75% ethanol was the most effective aqueous alcohol for PL extraction and enrichment from the yolk flakes. In the first stage of extraction using such a solvent, 67% of the total PL in the original yolk was recovered in a lipid fraction with a PL purity of 75%. This study identified the optimal ethanol concentration for PL extraction from dried egg yolk. With this information, the best solid:solvent ratio can be designed to extract and enrich the polar lipids from lipid-bearing materials with known moisture content using a renewable or “green” solvent, ethanol.     

The Fractional Extraction of Lipids and Cholesterol from Dried Egg Yolk Using Supercritical Carbon Dioxide

Results from extraction of cholesterol and other lipid components from dried egg yolk using supercritical carbon dioxide at the range of temperature from 40°C to 60°C and pressure between 150 bar und 350 bar for 2.5 hours and 2.7 kg CO₂ consumption is described in this paper. The solubility of lipids and cholesterol increased with the increase of pressure at a constant temperature of 50°C, while at a constant pressure, more cholesterol was removed at 45°C than that at other temperatures. Nearly 60 percent cholesterol was removed at 45°C and 250 bar. Lipids were more efficiently extracted at 60°C than at 40°C at 250 and 350 bar, however, a decrease in the total extracted lipids was observed with the increase in temperature at 150 bar. The removed total lipids from dried egg yolk at 250 bar/55°C was over 80 %.     

Lipid peroxidation in low density lipoproteins from human plasma and egg yolk promotes accumulation of 1-acyl analogues of platelet-activating factor-like lipids

Oxidative modification of low density lipoprotein (LDL) is known to be a key event for induction of atherosclerosis. However, there has been little progress in structural elucidation of oxidized lipids, especially oxidatively fragmented phospholipids retaining a glycerol backbone. In this study, we found that LDL derived from egg yolk has no platelet-activating factor (PAF) acetylhydrolase activity, and that prolonged incubation of egg yolk LDL with Cu²⁺ resulted in the formation of various PAF-like lipids: 1-acyl type phosphatidylcholines with ansn-2-short-chain dicarboxylate or monocarboxylate group. Only a very small amount of the PAF-like lipid having ansn-2-short-chain monocarboxylate group was detected by gas chromatography-mass spectrometry in Cu²⁺-oxidized LDL from human plasma with high PAF-acetylhydrolase activity, which has been reported to hydrolyze PAF-like lipids to lysophosphatidylcholines. Preincubation of plasma LDL with diisopropyl fluorophosphate dose-dependently inhibited PAF-acetylhydrolase activity, resulting in accumulation of the PAF-like lipids when the LDL was oxidized with Cu²⁺. As well as PAF and lysophosphatidylcholines, several PAF-like lipids were found to inhibit [³H]thymidine incorporation into cultured vascular smooth muscle cells derived from rat aorta. The possible formation of PAF-like lipids by lipid peroxidation in LDL is discussed as well as its possible significance for induction of atherosclerosis.     

Effect of soy oil supplementation and protein level in laying hen diets on praecaecal nutrient digestibility,performance, reproductive performance,fatty acid composition of yolk fat,and on other egg quality parameters

An experiment was carried out with laying hens in the age of 22—45 weeks to examine the effects of added soy oil (0%, 3.5%, 7%, 10.5%, and 14%) and dietary protein level (13.2% and 16.3%) on laying and reproductive performance, fatty acid composition of yolk fat, and other egg quality parameters. Moreover, digestibility of nutrients and of energy was determined by using a marker technique. Laying intensity and feed intake were not influenced by dietary treatments whereas egg weight and daily egg mass production were significantly improved by soy oil addition in a non‐linear related manner. The feed conversion ratio reached a minimum at soy oil proportions between 3.5% and 10.5%. Reproductive performance in terms of fertilized eggs, hatchability, and mortality of chicks was not affected by dietary treatments. The increase of egg weights due to soy oil addition was accompanied by a simultaneous increase in the proportion of albumen and a decrease of yolk and shell percentage. Palmitic acid (C16:0) and oleic acid (C18:1) proportions in yolk fat decreased as soy oil addition was increased whereas the proportions of linoleic acid (C18:2 n‐6), linolenic acid (C18:3 n‐3), and docosahexaenoic acid (C22:6 n‐3) were increased at the same time. Praecaecal digestibility of crude fat and fatty acids of the diets were non‐linearly improved by soy oil addition. Digestibility of crude protein and amino acids were not affected by either protein content of the diet or by soy oil supplementation. In conclusion, a decrease in dietary protein content from 16.3% to 13.2% did not negatively influence performance of hens and egg quality under the experimental conditions applied. Soy oil addition improved egg quality.     

Supercritical CO2 extraction of egg yolk: Impact of temperature and entrainer on residual protein

Differential scanning calorimetry (DSC) was used to monitor changes in protein conformation resulting from supercritical carbon dioxide (SC-CO₂) extraction of lipids from egg yolk. Extraction temperatures of 65°C and lower had no effect on protein conformation as indicated by similar denaturation temperatures and enthalpies of denaturation (ΔH). An extraction temperature of 75°C resulted in a reduction in the ΔH value for ovalbumin present in the egg yolk. The use of 3% methanol as an entrainer during extraction at 36 MPa and 40°C resulted in a 50% reduction in the ΔH value for ovalbumin. The use of high temperatures and/or entrainers during SC-CO₂ extraction can result in significant protein denaturation.     

Chromatographically homogeneous lecithin from egg phospholipids

Chromatographically homogeneous egg lecithin, as determined by TLC on Silica Gel G, has been isolated from crude egg phosphatides by column chromatography on alumina through modification of existing, lengthy methods. The modified method involved application of crude egg phosphatides to a column of alumina in the proportion of 1 g phosphatide/25 g alumina, and elution of the lecithin fraction with the 2-component solvent system chloroform:methanol, 9:1 by vol. This method of purification separated lecithin from other choline and non-choline components of crude phosphatides, avoided overloading of the alumina column, and made unnecessary the need for a second chromatographic fractionation of partially purified lecithin on silicic acid, which is needed in existing methods of purification of lecithin. The use of fresh yolks permitted easier removal of pigment from the final product than was possible with commercially dried yolks. Phosphatides extracted from dried yolks were much more highly colored than were the phosphatides extracted from fresh yolks and the color presisted through chromatography on alumina. The fatty acid/phosphorus molar ratio of the purified lecithin was 2.00, which is the theoretical FA/P molar ratio of phosphatidylcholine; other materials with this ratio were not present. Presented at the AOCS Meeting, New Orleans, 1964. A laboratory of the So. Utiliz. Res. & Dev. Div., ARS, USDA.     

Molecular species of phosphatidyl ethanolamine from egg yolk

Phosphatidyl ethanolamine was isolated from total egg yolk lipids by preparative thin layer chromatography (TLC). The purified phosphatide contained 3% of the alkoxy derivative. It was degraded to diglycerides in the presence of purified sphingomyelin by phospholipase C fromClostridium welchii. The diglycerides were acetylated and resolved on the basis of unsaturation by argentation TLC. The fatty acid composition of the original phosphatidyl ethanolamine and the derived acetates was determined by gas chromatography, as was the molecular weight distribution of the diglyceride acetates. The placement of the fatty acids in the parent phosphatide was deduced by hydrolysis with phospholipase A fromCrotalus atrox, and in the acetates with pancreatic lipase. Some 33 major species of phosphatidyl ethanolamine were identified and compared to those for egg yolk lecithins. Presented in part at the Canadian Federation of Biological Societies Meeting, Kingston, June 1968.     

Destabilization of Egg Yolk Emulsion After IgY Removal Through Enzymatic Treatments

The objective of this study was to destabilize the protein–lipid complex in egg yolk precipitate obtained after the removal of soluble proteins, referred to as the pellet, through enzymatic treatment for further phospholipids extraction. A combination of proteolytic and lipolytic enzymes was applied to release the lipids from the pellet or weaken the pellet emulsion. Emulsions prepared using Protease P/Lipase AY30, Protease II/Lipase AY30 and Protease M/Lipase AY30 treated pellets had larger oil droplets (78, 65, 56 µm) and higher coalescence rates (51, 41, 35 %) than those of Protex 51FP, pellet, Protex 7L and Protease A with oil droplet size of 20, 18, 15 and 13 µm and coalescence rates of 31, 8, 7.5 and 8 %, respectively. Cream and liquid subnatant fractions obtained after further centrifugation of hydrolysates were subjected to lipid analyses. Over 90 % of phosphatidylcholine (PC) present in the pellet and 80 % of that in the original egg yolk were recovered in the cream from Protease P/Lipase AY30 treatment, while the recovery of PC from the egg yolk was significantly lower in creams from Protex 7L or Protease 51FP treatments (12 and 10 %, respectively). Pellets treated with Protease M, Protex 7L or Protex 51FP in combination with Lipase AY30 led to a significant loss of PC due to the conversion of PC to lysophosphatidylcholine or its degradation. Cream fractions obtained from the study represented a better material for the recovery of PL than intact egg yolk using environmentally-friendly techniques such as supercritical carbon dioxide (SC-CO₂) extraction.     

Hen egg yolk and white contain high amounts of lysophosphatidic acids, growth factor-like lipids: Distinct Molecular species compositions

Hen egg yolk and white were found to contain high amounts of lysophosphatidic acid (acyl LPA) in addition to small amounts of lysoplasmanic acid (alkyl LPA). The levels of acyl LPA in hen egg yolk (44.23 nmol/g tissue) and while (8.81 nmol/g tissue) were on the same order as or higher than the levels of acyl LPA known to be required to elicit biological responses in various animal tissues. Noticeably, there is a marked difference between the fatty acid composition of egg yolk acyl LPA and of egg white acyl LPA; egg yolk acyl LPA predominantly contains saturated fatty acids as the acyl moiety, whereas egg white acyl LPA primarily contains polyunsaturated fatty acids. We found that the level of acyl LPA, especially polyun-saturated fatty acid-containing acyl LPA, in egg white was augmented markedly during the incubation at 37°C, while there was no change in egg yolk. We confirmed that egg white contains both the substrate, i.e., polyunsaturated fatty acid-containing lysophosphatidylcholine (LPC), and the enzyme activity catalyzing the hydrolysis of polyunsaturated fatty acid-containing LPC to the corresponding acyl LPA. Egg yolk LPA and egg white LPA may play separate physiological roles in the development, differentiation, and growth of embryos.     

Passive Immune-Protection of Litopenaeus vannamei against Vibrio harveyi and Vibrio parahaemolyticus Infections with Anti-Vibrio Egg Yolk (IgY)-Encapsulated Feed

Vibrio spp. are major causes of mortality in white shrimp (Litopenaeus vannamei) which is lacking adaptive immunity. Passive immunization with a specific egg yolk antibody (IgY) is a potential method for the protection of shrimp against vibriosis. In this study, immune effects of the specific egg yolk powders (IgY) against both V. harveyi and V. parahaemolyticus on white shrimp were evaluated. The egg yolk powders against V. harveyi and V. parahaemolyticus for passive immunization of white shrimp were prepared, while a tube agglutination assay and an indirect enzyme-linked immunosorbent assay (ELISA) were used for detection of IgY titer. Anti-Vibrio egg yolk was encapsulated by β-cyclodextrin, which could keep the activity of the antibody in the gastrointestinal tract of shrimp. The results showed that the anti-Vibrio egg powders had an inhibiting effect on V. harveyi and V. parahaemolyticus in vitro. Lower mortality of infected zoeae, mysis, and postlarva was observed in groups fed with anti-Vibrio egg powders, compared with those fed with normal egg powders. The bacterial load in postlarva fed with specific egg powders in seeding ponds was significantly lower than those fed with normal egg powders in seeding ponds. These results show that passive immunization by oral administration with specific egg yolk powders (IgY) may provide a valuable protection of vibrio infections in white shrimp.     

Incorporation of dietary linoleic and conjugated linoleic acids and related effects on eggs of laying hens

In the present study, laying hens received 29 g per kg diet of a preparation containing either 70% linoleic acid (LA) or approximately the same amount of conjugated linoleic acid (CLA) in the control and experimental treatments, respectively. The CLA preparation consisted predominantly of cis-9,trans-11 and trans-10,cis-12 fatty acid isomers as free fatty acids in a ratio of 1∶1. The diets were fed for 8 wk to determine the effect of dietary CLA on quality characteristics of eggs. In addition, the fatty acid composition of liver and heart was analyzed. Performance parameters (egg weight, feed efficiency) were not significantly affected by feeding the diets supplemented with CLA. The overall amount of CLA that was incorporated into yolk was 7.95 g CLA/100 g total fatty acids, or approximately 400 mg CLA/egg. The transfer efficiency of the cis-9,trans-11 isomer was higher than that of the trans-10,cis-12 isomer; however, the transfer rate of CLA isomers into yolk and tissues was significantly lower than that of linoleic acid. Dietary CLA increased the concentration of saturated fatty acids in yolk and tissues at the expense of monounsaturated fatty acids. The proportions of myristic, palmitic, and stearic acids in yolk lipids were also changed by dietary CLA. Additionally, long-chain polyunsaturated fatty acids (arachidonic acid and docosahexaenoic acid) were decreased without changing the balance of the n−6/n−3 ratio in egg yolk. The inclusion of CLA in layer diets altered the shape of the yolk and various egg parameters (albumen height, foam index, and yolk index). The results of this study indicate that CLA induces various changes in lipid and fatty acid metabolism of laying hens and affects quality characteristics of eggs.     

Methoden zur Phosphatidanalytik am Beispiel der Lipide aus Seren und Eigelb

Techniques of Phospholipid Analyses Applied to Sera and Egg Yolk Thin layer (TLC) and gas-liquid-chromatography (GLC) were used to analyse phospholipids and diglycerides prepared from phospholipids. TLC of lipids is carried out on silica gel and for diglycerides on silica gel impregnated with 10% AgNO₃. Fatty acids of individual lipids were identified by GLC. The recovery of lipids was evaluated after chromatography of phospholipids and diglycerides and after digestion with phospholipase-C from Bacillus cereus. Two techniques of acetylation with two different catalysts are compared. The calculations were referred to phosphorus or glycerol in lipids. The precise amount of phospholipids was determined after charring as inorganic phosphorus. Diglycerides were assayed after saponification by an enzymatic determination of glycerol. The reliability of some lipid techniques could be shown. The values of phospholipids for egg yolk and sera are in correspondence to literature.