Casein

Casein is the main phosphoprotein in milk, forming about 80% of the total protein in cow’s milk and serving as the primary structural and nutritional protein in cheese curd.​

Nature and composition

Casein is a family of related proteins (αs1-, αs2-, β-, and κ-casein) that occur in milk as calcium–phosphate–protein complexes called casein micelles, which keep calcium and phosphate stably dispersed.​

In pure or commercial form it appears as an amorphous white to yellowish, tasteless, nearly odourless solid, usually produced by precipitating it from skim milk with acid or rennet.​

Functional properties and food uses

Casein is amphiphilic and acts as an excellent emulsifier, stabiliser, and texturiser; its salts (e.g., sodium or potassium caseinate) are widely used to stabilise dairy drinks, sauces, processed cheese, desserts, and instant powders.​

Nutritionally, casein is a complete, slow‑digesting protein supplying all essential amino acids along with significant calcium and phosphorus, so it is commonly used in protein supplements, diet products, and sports nutrition.​

Technical and industrial uses

Technical or industrial casein is used beyond food in adhesives, paper coatings, paints, plastics, leather finishing, and textile sizing because it forms strong, flexible films and binds pigments well.​

Its ability to form stable films and bind calcium also underlies specialised uses in pharmaceuticals, cosmetics, and oenology (e.g., caseinate fining agents in wine)