albumin [Lat.,=white of egg], member of a class of water-soluble, heat-coagulating proteins. Albumins are widely distributed in plant and animal tissues, e.g., ovalbumin of egg, myogen of muscle, serum albumin of blood, lactalbumin of milk, legumelin of peas, and leucosin of wheat. Separation of serum albumins from other blood proteins can be carried out by electrophoresis or by fractional precipitation with various salts. Albumins normally constitute about 55% of the plasma proteins. They adhere chemically to various substances in the blood, e.g., amino acids, and thus play a role in their transport. Albumins and other proteins of the blood aid significantly in regulating the distribution of water and maintenance of proper osmotic pressure in the body. Albumins are also used in textile printing, in the fixation of dyes, in sugar refining, and in other important processes.

Any of a diverse class of proteins historically defined by their ability to dissolve in water and in a half-saturated (see saturation) solution of ammonium sulfate. They are readily coagulated by heating. Examples include serum albumin, a major component of plasma; α-lactalbumin, found in milk; ovalbumin, which makes up about half the proteins of egg white; and conalbumin, another egg-white protein. Ovalbumin is used commercially in the food, wine, adhesives, paper coatings, pharmaceutical, and other industries and in research.

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