Whey proteins are much more water-soluble than casein proteins. Regular margarine contains trace amounts of animal products such as whey or dairy casein extracts. That effect is somewhat overcome by combining casein and whey. These casein proteins form a multi molecular colloidal particle known as a casein micelle. This protein may function in the inhibition of casein kinase. The most common form of casein is sodium caseinate. It also results in decreased casein, the major protein in milk. Most of the casein proteins are bound into the micelles. Chymosin, its key component, is a protease enzyme that curdles the casein in milk. The stability of milk is largely due to the electrostatic repulsion of casein micelles. Trypsin can be used to break down casein in breast milk. Caseinates are produced by adding an alkali to another derivative of casein, acid casein. A small fraction of the population is allergic to casein. Cleavage causes casein to stick to other cleaved casein molecules and form a network.