Egg Yolk, F75

Bird eggs are a common food source. The most commonly used bird eggs are those from the chicken, duck, and goose, but smaller eggs such as quail eggs are occasionally used as a gourmet ingredient – as are the largest bird eggs, from ostriches. Most commercially-produced chicken eggs intended for human consumption are unfertilised, since the laying hens are kept without any roosters. Fertile eggs may be eaten as well, with little nutritional difference. Fertile eggs will not contain a developed embryo, as refrigeration prohibits cellular growth. Chicken eggs are widely used in many types of cooking. Eggs may be pickled; hard-boiled, scrambled, fried and refrigerated; or eaten raw; though the latter is not recommended for people who may be susceptible to salmonella, such as the elderly, the infirm or pregnant women. Hen’s egg is comprised of about 8-11% shell, 56-61% white and 27-32% yolk. (1, 2, 3, 4, 5) In addition, the protein in raw eggs is only 51% bio-available, whereas cooked egg protein is nearer 91% bio-available, meaning the protein of cooked eggs is nearly twice as absorbable as the protein from raw eggs.

Foods that may contain egg include salad dressings, breads, breaded foods, muffins, pancakes, waffles, meringues, marshmallows, prepared soups and beverages, frostings, ice creams and sherbets, pie fillings, sausages, prepared meats, mayonnaise, coatings and breading for fried foods, tartar and hollandaise and other sauces.

Egg yolks are used to make mayonnaise and other dishes high in fat. Egg yolks are important as binding agents in many preparations in European cooking due to the emulsifying action of lecithin. This property is crucial for mayonnaise and sauces such as Béarnaise, and hollandaise; custards such as crème anglaise, crème brûlée, crème caramel, lemon custard and key lime pie; and meat dishes such as pâté and meatloaf. 

Foods that may contain egg include candy, salad dressings, breads, breaded foods, muffins, pancakes, waffles, meringues, marshmallows, prepared soups and beverages, frostings, ice cream and sherbets, pie fillings, sausages, prepared meats (sausages, patês) (egg as a binding agent), mayonnaise, coatings and breading for fried foods, tartar and hollandaise and other sauces.

Although the main allergens in egg are found in the Egg white, Egg yolk also contains a large number of specific IgE-binding allergens. Three proteins (apovitellenins I & VI and phosvitin) have been shown to bind IgE from the sera of persons with specific IgE to Egg yolk. Both common and distinct allergenic molecules are present in egg. This was demonstrated in a study of 11 patients with a history of egg allergy, in whom all sera reacted positively to both Egg white and Egg yolk. Eight patients reacted equally or more strongly to Egg white, and even though each could inhibit the IgE binding of the other to some degree, Egg yolk could only be partially inhibited by Egg white in eight sera. 

• Postpone the process of testing immediately after paraclinical studies (roentgen, TC, MRI) and physiotherapy procedures. They can affect test results.

• We recommend avoiding physical activity prior to your examination.