Casein: Casein, also known as casein, is a kind of protein polymer produced when milk meets acid. Casein accounts for about 80% of the total protein of milk and 3% by mass, and it is also the main component of cheese. Casein is a tasteless white or yellowish amorphous powder. Casein is slightly soluble in water, but soluble in alkali liquor and acid liquor.

The amino acid composition of casein is (in percentage) Ala alanine 2.7, arg arginine 3.7, Asp aspartic acid 6.4, Cyscystine 0.3, Glu glutamic acid 20.2, Gly glycine 2.4, His histidine 2.8, Isoisoleucine 5.5, Leu leucine 8.3, Lys lysine 7.4, Met methionine 2.5 and Phe phenylalanine 4.5. Proline 10.2, serine 5.7, threonine 4.4, tryptophan 1. 1, tyrosine 5.7 and valine 6.5.

Application of casein: Casein has a wide range of uses, which can be used as food additives, casein glue, watercolor, paper making, textile, leather and so on. By reacting with formaldehyde, its derivatives can be used in plastic products, such as buttons and other small plastic products.