In egg yolk

Lecithin is widely used as an emulsifying agent, allowing oil and water to mix. It is used in ice creams, salad dressings, and cosmetics, and it is the main ingredient in nonstick cooking sprays. Lecithin is the emulsifier in egg yolks that allows the oil and water to mix to make mayonnaise. 

Verheyen, G., J. Helsen, and E. Decuypere. 1990. Accumulation of zinc in egg yolk ovarian follicles and organs after forced resting by high dietary zinc. Brit. Poult. Sci. 31 147-154. 

CAROTENOID CONCENTRATIONS IN EGG YOLK FROM GULL, MOORHEN AND COOT AND IN TISSUES OF NEWLY HATCHED MOORHEN, COOT AND GULL... 

Histamine may also be found in egg yolk, although levels are very low. Fresh eggs contain the highest level of histamine, 0.078 mg per 100 g, while stored eggs contain 0.063 mg per 100 g and boiled eggs contain 0.046 mg per 100 g of histamine (Moudgal et al., 1991). 

TMA is normally formed from dietary choline and lecithin, but also from TMA N-oxide by intestinal bacteria (Fig. 7.4.2). Choline bound to lecithin is present most abundantly in egg yolk, liver, kidney legumes, soy beans and peas. TMA N-oxide is present in considerable amounts in marine fish, amounting to approximately... 

Following oral administration, furaltadone is well absorbed from the gastrointestinal tract. After administration to laying hens of a medicated feed containing 100 mg/kg each nitrofurazone, furazolidone, nitrofurantoin, and furaltadone for 7 days, residues of furaltadone in egg yolk showed a maximum concentration of 0.2 ppm (129). 

In this assay, milk samples could be analyzed without dilution, but tissue and egg white samples should be homogenized in 5% trichloroacetic acid, centrifuged, and brought to pH 7 prior to analysis. Egg yolks required a separate treatment involving mixing with a pH 7.4 phosphate-EDTA buffer, incubation for 3 h at 25 C with cephalexin antiserum and enzyme-label cephalexin, and centrifugation. The assay could detect cephalexin down to 30 ppb in milk, 60 ppb in egg yolk, and 400 ppb in hen tissue. 

The adaptation of methods for lipid extraction and quantification by colorimetric determination of either ester or cholesterol in egg yolk with some contamination of egg white is described. Results are compared with those obtained by a conventional enzymatic determination. 

Pasin, G., Smith, G.M., and O Mahony, M. 1998. Rapid determination of total cholesterol in egg yolk using commercial diagnostic cholesterol reagent. Food Chem. 61 255-259. 

P Mattila, V Piironen, E Uusi-Rauva, P Koivistoinen. Determination of 25-hydroxycholecalciferol in egg yolk by HPLC. J Food Comp Anal 6 250-255, 1993. 

Transferring and a decreasing profile of SQX in eggs was the aim of several studies (181,182). The drug content reached a plateau after 4 days of SQX feeding the residue content began to decrease 1 day after the withdrawal of dietary SQX. However, the disappearance profile in albumen was different from that in egg yolk. 

Phosvitin is a highly phosphorylated, iron-containing protein found in egg yolk and serves as an important source of dietary iron.1138 It could be viewed as a source of phosphate, as the protein contains about 130 residues of phosphoserine which appear to serve as ligand groups for iron. 

Lucerne is one of the most widely grown forage crops on a worldwide basis and is used commonly in livestock diets. It is a good source of many nutrients and in the past the inclusion of lucerne meal was considered to be essential in diets for a wide range of animals as a source of unidentified factors. Currently lucerne meal is used in poultry diets as a source of pigments to provide a yellow colour in egg yolks, shanks and skin (e.g. Karadas et al, 2006). 

Kim, E.M., Choi, J.H. and Chee, K.M. (1997) Effects of dietary safflower and perilla oils on fatty acid composition in egg yolk. Korean Journal of Animal Science 39,135-144. 

Traditional mayonnaise is an 80% oil-in-water emulsion, which may rely on mustard seeds for solid particle stabilization. Two constituents of egg yolk, lecithin and cholesterol, are surfactants, which promote the formation of oil-in-water and water-in-oil emulsions, respectively. The ratio of lecithin to cholesterol in egg yolk favors the water-in-oil type but the final emulsion type formed is due to the action of mustard seed, which favors an oil-in-water emulsion (Petrowski, 1976). 

Morgan J.N., Armstrong, D.J. 1992. Quantification of cholesterol oxidation products in egg yolk powder spray-dried with direct heating. J. Food Sci. 57, 43-45. 

Modern in vitro fermentation technologies can compete with in vivo production of antibodies regarding concentration and purity of the produced material. In fact, a number of more sophisticated methods of antibody expression have been developed in the last decade the most important are cell culture in protein-free media and the expression in the milk of transgenic animals, in transgenic plants, and in egg yolk. 

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