Casein

Casein (/ˈkeɪsiːn/ KAY-seen, from Latin caseus "cheese") is a family of related phosphoproteins (αS1, aS2, β, κ) that are commonly found in mammalian milk, comprising about 80% of the proteins in cow's milk and between 20% and 60% of the proteins in human milk. Sheep and cow milk have a higher casein content than other types of milk with human milk having a particularly low casein content.

Casein is the primary emulsifier in milk, that is, it helps in mixing oils, fats, and water in milk.

Casein has a wide variety of uses, from being a major component of cheese, to use as a food additive. The most common form of casein is sodium caseinate, which is a very efficient emulsifier. Casein is secreted into milk from mammary cells in the form of colloidal casein micelles, a type of biomolecular condensate.

As a food source, casein supplies amino acids, carbohydrates, and two essential elements, calcium and phosphorus.