Egg White, F1

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 can 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. Egg white is the common name for the clear liquid (also called the albumen) contained within an egg. The protein in raw eggs is only 51% bio-available, whereas a cooked egg has nearer 91% protein 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 cream and sherbets, pie fillings, sausages, prepared meats (egg as a binding agent), 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.

The albumen or egg white contains protein but little or no fat. It is used in cooking separately from the yolk, and can be aerated or whipped to a light, fluffy consistency. Beaten egg whites are used in desserts such as meringues and mousse.

Egg white has been considered the most important source of allergens, but IgE-binding allergens have also been described in egg yolk, suggesting that both common and distinct allergenic molecules are present. This was demonstrated in a study of 11 patients with a history of egg allergy, in all of whom sera reacted positively to both white and yolk. Eight patients reacted equally or more strongly to white, and even though white and yolk could each inhibit the IgE binding of the other to some degree, yolk could only be partly inhibited by 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.