Curdling the separation of an emulsion such as milk or mayonnaise. Cooks normally use the word when something has gone wrong, but the deliberate curdling of milk is part of the normal process of making cheese and other milk products. The term is also used vaguely for various misfortunes that produce a lumpy texture. Other words used in this context are flocculation, which means the formation of any kind of lumpy or fluffy masses and is understood here to mean a lumpiness that can be reversed; and coagulation, which means an irreversible hardening—if a sauce coagulates, the only thing to do is throw it away and start again. The term coagulation is normally used only of protein.
