Casein

The main protein found in milk and other dairy products.

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The principal protein of cow's milk and the chief constituent of cheese. It is insoluble in water, soluble in dilute alkaline and salt solutions, forms a hard insoluble plastic with formaldehyde, and is used as a constituent of some glues; various components are designated α-, β-, and κ-caseins. β-C. is converted to γ-c. by milk proteases. There are several isoforms of α-c.. κ-C. is not precipitated by calcium ions.

- c. iodine, iodinated c. a compound of c. with iodine formed by incubating the protein with the element, which becomes attached to tyrosine groups in the protein. SYN: caseo-iodine.

- plant c. SYN: avenin.

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ca·sein 'kā-.sēn, ka-'sēn n any of several phosphoproteins of milk: as

a) one that occurs as a colloidal suspension in milk called also caseinogen

b) one that is produced when milk is curdled by rennet, is the chief constituent of cheese, and is used in making plastics called also paracasein

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n.

a milk protein. Casein is precipitated out of milk in acid conditions or by the action of rennin: it is the principal protein of cheese. Casein is very easily prepared and is useful as a protein supplement, particularly in the treatment of malnutrition.

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ca·sein (kaґsēn) [L. caseus cheese] a phosphoprotein, the principal protein of milk, the basis of curd and of cheese. It is precipitated from milk as a white amorphous substance by dilute acids, and redissolves on the addition of alkalis or of excess acid. Rennin (and other milk-clotting enzymes) influence the hydrolysis of casein to soluble paracasein, which in the presence of calcium (Ca²⁺) is converted to an insoluble curd (insoluble paracasein or calcium paracaseinate). Casein, usually in the form of its calcium, potassium, or sodium salts, is added to other ingredients of the diet to increase its protein content. NOTE: In British nomenclature, casein is called caseinogen, and paracasein is called casein.