Casein is a family of related phosphoproteins that are commonly found in mammalian milk, comprising about 80% of the proteins in cows milk and between 20% and 60% of the proteins in human milk. It is a protein found in milk and dairy products, and it accounts for roughly 80% of the protein in milk, cheese, and yogurt. Casein is a complete protein and has all nine essential amino acids. It is a slower-digesting protein than whey, forming a gel-like substance in the stomach and releasing more slowly than other proteins, taking longer for the body to absorb. Casein protein is taken by mouth to improve athletic performance, diabetes, liver disease due to alcohol consumption, and many other conditions, but there is no good evidence to support these uses.

Some of the key features of casein include:

• Composition: Casein contains a high number of proline amino acids which hinder the formation of common secondary structural motifs of proteins. There are also no disulfide bridges. As a result, it has relatively little tertiary structure. It is relatively hydrophobic, making it poorly soluble in water.

• Uses: Casein protein is found in yogurt, cheese, and infant formulas, as well as in a variety of dietary supplements. It is used in powders requiring rapid dispersion into water, ranging from coffee creamers to instant cream soups. Mead Johnson introduced a product in the early 1920s named Casec to ease gastrointestinal disorders and infant digestive problems which were a common cause of death in children at that time.

• Benefits: Casein protein provides the body with all of the amino acids necessary to help build muscle. It is also known to reduce appetite and increase feelings of fullness.

• Side Effects: Casein protein is generally safe for most people when taken in appropriate amounts. However, some people may experience allergic reactions, digestive issues, or other side effects.

In addition to its uses in food and dietary supplements, casein paint is a fast-drying, water-soluble medium used by artists. It has been used since ancient Egyptian times as a form of tempera paint and was widely used by commercial illustrators as the material of choice until the late 1960s when, with the advent of acrylic paint, casein became less popular. It is still widely used by scenic painters, although acrylic has made inroads in that field as well.