Albumin is an family of proteins. Many types can be found all over the natural world, and two of the most familiar examples can be found in egg whites and in human blood. Albumins are an important class of protein, and they are vitally important to health and well being for many organisms. Many plants and animals contain or secrete this protein.
A protein classified as albumin is globular, meaning that it has a roughly spherical structure. When combined with water, such proteins form a colloid, a solution that appears homogeneous although it actually contains multiple substances. The other type of protein, fibrous protein, such as that found in muscles, is not water soluble, and it has a different basic structure.
Within the human body, albumin is an important component of life. It transports essential fatty acids from adipose tissue, otherwise known as fat, to muscle tissue. The protein also contributes to the regulation of osmosis, helping to transport hormones, drugs, and other substances through the blood. A deficiency can lead to medical issues, and medical professionals may request a blood albumin test when investigating a patient's medical condition.
Technically, the albumin found in egg whites is more formally known as ovalbumin. This should not be confused with albumen, which is another name for egg whites in general. A little more than half of the protein found in egg whites are ovalbumin.
When heated, albumin and other proteins tend to coagulate. This property proves very useful in cooking, and it is one of the reasons why eggs are so frequently used in baking. The protein helps baked goods hold their structure. The protein in egg whites is also used for purification, as it tends to trap and store impurities. Egg whites are used to refine dishes like soup, and to treat people with certain types of poisoning, since it binds to the toxin.
When it is cooked, the proteins begin to unfold, recombining in a new configuration; it also turns white and opaque. When beaten, the ovalbumin unfolds partially, creating a filmy foam that encloses pockets of air. As anyone who has beaten eggs too much is aware, when the proteins are beaten too much, they unfold completely and lose structure. Since this protein is flexible, it expands with the air trapped inside the pockets as it bakes, and it will retain the larger shape and yield a light, fluffy texture.