Casein

Casein (Latin caseus, cheese ', also in the spelling of casein ) is the name for those protein content of the milk of the higher mammals, which does not enter the whey and the example further processed into cheese. It is a mixture of several proteins ( αS1, αS2, β -, κ -casein ), and used, inter alia the storage and transport of protein, calcium and phosphate to the newborn. Casein in milk is combined with calcium phosphate, and other components known as micelles, which keep dissolved the calcium phosphate, and aggregate the milk in the stomach into a lump, which facilitates digestion.

Casein makes up the majority of the proteins in quark (curd cheese ) and cheese obtained by coagulation of casein its firm consistency. Casein is used not only as a food but also as a binder and a pharmaceutical excipient. Casein is one of the most common causes of cow's milk allergy. The caseins are the most common milk proteins, which account for about 80 % of the total amount of protein in milk. The remaining proteins are summarized as whey proteins.

Components and composition

As an example, the following table lists the components of cow casein.

In contrast to cow's milk in human milk, the β - and κ -casein, the major proteins. The following table contains details and links on casein in human milk.

Biological Significance

Casein is the main protein, calcium and phosphate source for the young mammal. Cow's milk contains 2.6% casein ( ie about 26 g / L; einmägigen in mammals significantly less ) and accounts for about 80% of total milk protein from.

Degradation and digestion

By heating, the addition of acid or enhanced by the addition of the enzyme pepsin, a partial degradation of the casein takes place, what cheese and curd makes it easier to digest than raw milk.

Casein can act as an allergen and cause very severe, even life-threatening reactions in people. An allergy to casein is quite rare to see. This is not to be confused with lactose intolerance, in which it is an enzyme related intolerance to lactose.

The digestion of casein is very slow. It may be up to eight hours. This advantage make athletes (especially bodybuilders ) as its own, to (overnight for example ) to achieve an amino acid supply for several hours.

Furthermore, it seems that some people casein (as well as gluten, ie cereal gluten ) can not fully digest, and that in this case the remaining undigested peptides also exorphins called on the brain and nervous system of the human opioid - like action unfold.

Technical recovery

Native casein is mainly obtained by microfiltration. As the separation criterion was used, the particle size. The retentate mainly remain caseins and minor fractions of whey protein and lactose in the permeate are mainly mineral salts, lactose, whey proteins and small amounts of Caseinsubmicellen.

Denatured or functionally modified casein or caseinate can be produced using an acid precipitation and subsequent neutralization using calcium hydroxide, potassium hydroxide or sodium hydroxide solution. By filtration or centrifugation, the denatured casein is then separated off. In most cases the protein to be precipitated by various methods previously concentrated.

Technical use

Casein is technically used in addition to the use as a food and as raw material for various processing purposes. In particular, plays its use as a binder in casein as casein (eg as Etikettierleim in the labeling ) as well as photoresist in etching a role. Casein glue has apparently been used by the Chinese and Egyptian carpenters of antiquity for gluing furniture. Dyers used casein as a binder in the dyeing of leather and fabrics.

From the late 19th century until the 1930s it was the starting material for the plastic DPN, which was used among others for buttons and jewelry, but also for insulation for electrical installations. Or casein peptone from casein used in microbiology for the part as a component of nutrient media or nutrient solutions for cultivating microorganisms, for example, in the casein soybean peptone agar.