What albumin means
Albumin is the name for a group of proteins that dissolve in water and set when heated. They are found in many foods, including egg white, milk, blood, meat, fish and some seeds. The best known in the kitchen is ovalbumin, the main protein in egg white, which is why the words albumin and albumen are so often confused. Albumen is the egg white itself, while albumin is the protein.
Cooks rarely use the word albumin in recipes, but they deal with it all the time. When eggs are cooked, albumin proteins unfold and bond together, turning runny whites into a firm, opaque solid. When meat or bones are simmered for stock, albumin and other proteins rise to the surface as grey foam, which cooks skim off for a clearer result. The white curds that sometimes appear on the surface of cooked salmon are albumin squeezed out of the flesh as the muscle contracts in the heat.
Cooking the fish more gently, or brining it briefly first, helps keep it inside. The word is mainly used in food science writing, baking books and explanations of why foods behave as they do, rather than in everyday recipes.