Progress in the Chemistry of Casein

Casein from cow's milk is not a single substance, but can be resolved into numerous components. These include x‐casein, which is the only fraction that contains appreciable quantities of sugars. This component plays a very important role in the clotting of milk by rennin, when it is split into an almost sugar‐free fraction, para‐x‐casein, and a fraction containing sugars, x‐caseinoglycopeptide. Caseinoglycopeptides have been isolated not only from the casein of cow's milk, but also from the caseins of sheep. Goat, and human milk. The second part of the paper deals with the clotting of milk by rennin and the amino acid sequence in caseinoglycopeptides.