casein

casein , well-defined group of proteins found in milk, constituting about 80% of the proteins in cow's milk, but only 40% in human milk. Casein is a remarkably efficient nutrient, supplying not only essential amino acids, but also some carbohydrates and the inorganic elements calcium and phosphorus. The calcium caseinates form an insoluble white curd when acidified by hydrochloric acid or sulfuric acid, or when milk is soured by bacterial contaminants. Acid casein is used widely in cheese, adhesives, water paints, for coating paper, and in printing textiles and wallpaper. In neutral solutions the enzyme rennin converts one of the caseins to an insoluble curd; most of the protein in cheese is rennet casein curd. When treated with formaldehyde the curd forms casein plastic, used for manufacturing imitation tortoiseshell, jade, and lapis lazuli.

casein (kay-si-in) n. a milk protein. Casein is precipitated out of milk in acid conditions or by the action of rennin. It is very easily prepared and is useful as a protein supplement, particularly in the treatment of malnutrition.

casein About 75% of the proteins of milk are classified as caseins; a group of 12–15 different proteins. Often used as a protein supplement, since the casein fraction from milk is more than 90% protein.