Sodium Caseinate aka Casein is a phosphoroprotein commonly found in animal and human milk. Unlike many proteins, casein is not coagulated by heat but by a chemical reaction. It is often used in cheesemaking for clotting. It is also used as a protein helper with transglutaminase to improve the bond of the meat glue.
Note: people who have allergies to milk may have a reaction to casein.