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Egg white is the clear liquid (also called the albumen or the glair/ glaire) contained within an egg. In , it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg.Ornithology, Volume 1994 By Frank B. Gill p. 361 It forms around fertilized or unfertilized yolk. The primary natural purpose of egg white is to protect the yolk and provide additional nutrition for the growth of the embryo (when fertilized). Egg white consists primarily of about 90% water into which about 10% (including , , and ) are dissolved. Unlike the yolk, which is high in (fats), egg white contains almost no fat, and carbohydrate content is less than 1%. Egg whites contain about 56% of the protein in the egg. Egg white has many uses in food (e.g. meringue, mousse) as well as many other uses (e.g. in the preparation of such as those for influenza).
| +Protein content of egg white |
| 54% |
| 12% |
| 11% |
| 4% |
| 4% |
| 3.5% |
| 3.4% |
| 1.5% |
| 1% |
| 0.8% |
| 0.5% |
| 0.05% |
| 0.05% |
Denaturation occurs as the whisk drags the liquid through itself, creating a force that unfolds the protein molecules.
Coagulation comes from the mixing of air into the whites, which causes the proteins to come out of their natural state. These denatured proteins gather together where the air and water meet and create multiple bonds with the other unraveled proteins, and thus become a foam, holding the incorporated air in place; because the proteins consist of , some are hydrophilic (attracted to water) and some are hydrophobic (repelled by water).
When beating egg whites, they are classified in three stages according to the peaks they form when the beater is lifted: soft, firm, and stiff peaks. Overbeaten eggs take on a dry appearance, and eventually collapse. Egg whites do not beat up correctly if they are exposed to any form of fat, such as or the fats contained in egg yolk.
Copper bowls have been used in France since the 18th century to stabilize egg foams. The copper in the bowl assists in creating a tighter bond in reactive sulfur items such as egg whites. The bond created is so tight that the sulfurs are prevented from reacting with any other material. A silver-Plating bowl has the same result as the copper bowl, as will a pinch of powdered copper supplement from a health store used in a glass bowl. Drawbacks of the copper bowl include the expense of the bowl itself, and that the bowls are difficult to keep clean. Copper contamination from the bowl is minimal, as a cup of foam contains a tenth of a human's normal daily intake level.
Eggs are susceptible to Salmonella contamination. Thorough cooking eliminates the direct threat (i.e. cooked egg whites that are solid and not runny), but the threat of cross-contamination remains if people handle contaminated eggs and then touch other foods or items in the kitchen, thus spreading the bacteria. In August 2010, the FDA ordered the recall of 380 million eggs because of possible Salmonella contamination.
Cooked eggs are a good source of biotin. However, daily consumption of raw egg whites for several months may result in biotin deficiency, due to their avidin content, as the avidin tightly binds biotin and prevents its absorption.
The albumen from egg white was used as a binding agent in early photography during an 1855-90 period; such prints were called .
In the 1750s, egg whites were believed to prevent swelling, and were used for that purpose. To help soothe areas of skin that were afflicted, egg white mixed with Armenian bole could help restore the fibers. Egg whites are also used in bookbinding during the gilding process, where it is referred to as 'glaire', and to give a book cover shine.
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