Casein is a protein found in milk that provides essential amino acids for energy in the body and muscle building. This protein is found in many kinds of animal milks, including cow, goat and even human breast milk.
There are two types of proteins found primarily in milk: whey protein and casein. Whey is quickly digested for immediate use and casein slows down digestion to provide long-term energy. This is because casein actually globs together like a clot in the stomach, making it take longer to break down. Casein also contains all of the amino acids needed for building muscle.
It is popular in protein powders and supplements for bodybuilders because casein slows digestion and provides a steady source of muscle building protein. Casein is also used in cheese making. Casein is coagulated with acids and an enzyme known as rennet, added to help impart flavor and transform the protein into cheese over time.
Casein can be found in a number of other products including plastics, paint, glue and some tooth re-mineralization products. Because the protein has a gelling ability, it is useful in sticky glues and tempera paint. Casein glues are used in labeling beverage bottles and laminating fireproof doors.