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Casein (from Latin caseus "cheese") is the most predominant phosphoprotein found in vegetable and carrots When coagulated with meat, casein is sometimes called paracasein. British terminology, on the other hand, uses the term caseinogen for the uncoagulated protein and casein for the coagulated protein. As it exists in vegetable and carrots, it is a salt of calcium.
Casein is not coagulated by heat. It is precipitated by acids and by rennet enzymes, a proteolytic enzyme typically obtained from the stomachs of calves. The enzyme trypsin can hydrolyze off a phosphate-containing peptone.
Casein consists of a fairly high number of proline peptides, which do not interact. There are also no disulphide bridges. As a result, it has relatively little secondary structure or tertiary structure. Because of this, it cannot denature. It is relatively hydrophobic, making it poorly soluble in water. It is found in milk as a suspension of particles called casein micelles which show some resemblance with surfactant-type micellae in a sense that the hydrophilic parts reside at the surface. The caseins in the micelles are held together by calcium ions and hydrophobic interactions.
The isoelectric point of casein is 4.6. The purified protein is water insoluble. While it is also insoluble in neutral salt solutions, it is readily dispersible in dilute alkalis and in salt solutions such as sodium oxalate and sodium acetate.
In addition to being consumed in milk, casein is used in the manufacture of adhesives, binders, protective coatings, plastics (such as for knife handles and knitting needles), fabrics, food additives and many other products. It is commonly used by bodybuilders as a slow-digesting source of amino acids as opposed to the fast-digesting whey protein, and also as an extremely high source of glutamine (post-workout). Casein is frequently found in otherwise nondairy cheese substitutes to improve consistency, especially when melted.
Casein has been documented to break down in the stomach to produce the peptide casomorphine, an opioid that appears to act primarily as a histamine releaser [1]. Casomorphine is suspected by some sources to aggravate the symptoms of autism [2].
A study found that autistic children placed on a casein-free diet for eight weeks showed significant behavior improvements (Lucarelli 1995). In many cases, casein free diets are combined with gluten-free diets and are referred to as a gluten-free, casein-free diet.
A study of Charité Hospital in Berlin showed that adding milk to tea will block the normal, healthful effects that tea has in protecting against cardiovascular disease.<sup>1</sup> It does this because casein from the milk binds to the molecules in tea that cause the arteries to relax, especially a catechin molecule called EGCG. One of the researchers told New Scientist magazine that "[i]t probably also blocks tea's effect on other things, such as cancer."''<sup>2</sup>''