coagulation A process involving the denaturation of proteins, the loss of their native, soluble structure, so that they become insoluble; it may be effected by heat, strong acids and alkalis, metals, and other chemicals. Some proteins are coagulated by specific enzymic action; the action of chymosin in cheese making is to coagulate the proteins of milk.

The final stage in blood clotting is the precipitation of insoluble fibrin, formed from the soluble plasma protein fibrinogen. The enzyme responsible is prothrombin, which is normally inactive, but in response to injury is activated by a cascade of events. Vitamin K is required for the synthesis of prothrombin, and clotting requires calcium ions. See also blood plasma.

coagulation The process in which colloidal particles come together irreversibly to form larger masses. Coagulation can be brought about by adding ions to change the ionic strength of the solution and thus destabilize the colloid (see flocculation). Ions with a high charge are particularly effective (e.g. alum, containing Al³⁺, is used in styptics to coagulate blood). Alum and iron(III) sulphate are also used for coagulation in sewage treatment. Heating is another way of coagulating certain colloids (e.g. boiling an egg coagulates the albumin). See also blood clotting.

coagulation The clumping together of colloidal particles to form a large mass; it may be caused by heating (e.g. the cooking of an egg causes the albumin (the ‘white’) to solidify) or by the addition of ions that neutralize the electrical charge which stabilize the colloid. See also BLOOD CLOTTING.

coagulation The clumping together of colloidal particles to form a large mass; it may be caused by heating (e.g. the cooking of an egg causes the albumen (the ‘white’) to solidify) or by the addition of ions that neutralize the electrical charge which stabilizes the colloid.

coagulation (koh-ag-yoo-lay-shŏn) n. the process by which a colloidal liquid changes to a jelly-like mass. See blood coagulation.