Merck, C7078-500G, Casein from bovine milk

Casein from bovine milk is a phosphoprotein. There are four main types of casein which make up approximately 80% of the total protein in bovine milk: α-ₛ₁ Casein, α-ₛ₂ Casein, β-Casein, and κ-Casein. Casein is proposed to be the main protective constituent in milk and is generally recognized as safe (GRAS) due to its naturally biocompatible and biodegradable properties.