Casein in milk

A method for the preparation of protein from milk by acid precipitation was described in 1838 by J.G Mulder, who coined the term ‘protein’. The acid-precipitated protein is referred to as casein.

Casein is the primary protein of milk comprising approximately 80% of the milk protein.  It is found in no product other than milk.

Beta casein is one of the major caseins in cow’s milk. Broadly, beta casein may be present as either A1 or A2 beta casein. Most cow in Australia produce milk with a combination of A2 and A1 beta-casein.

Casein is a phosphorus-containing protein that is heat stable, but precipitated by alcohol, rennet and acids.

The caseins are actually a group of similar proteins, which can be separated from the other milk proteins by acidification to a pH of 4.6.

At this pH, the caseins aggregate, since they are hydrophobic, are poorly hydrated and carry no net charge.

Individual fractions are combined into larger units called casein micelles, structure and stability of which are related to calcium content.

Casein in uncooled cow’s milk is present in spherical particles with a diameter of about 20 to 600 nm, comprised of 20 to 150,000 casein molecules. The inorganic matter of casein micelles, mainly colloidal calcium phosphate, is about 8 g/100 g casein,

In cheese making, most of the casein is recovered with the milk fat.
Casein in milk