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Casein protein

Dairy products, especially milk, are a major contributor to the dietary intake of humans, again particularly in western world populations. Milk contains numerous components of nutritional and health benefit. The basic component of milk is characterized by casein, which in basic terminology represents a group of proteins obtainable by milk precipitation at acid pH and up to room temperature, specifically pH 4.6 and 20 degree. C. Casein is a mixture of phosphoproteins naturally occurring in milk, cheese, beans and nuts. It is usually isolated from skim milk by isoelectric precipitation or by enzymatic coagulation. The isolated and recovered protein contains all of the common amino acids and is particularly rich in essential amino acids. Human milk differs markedly from that of other mammalian species, including cows, in that it contains a lower over-all protein content and lower ratio of casein/whey as well as a different protein composition. Caseins represent approximately 80% of total cow's milk proteins and 40% p/v human milk. Casein is not a single protein but a group of proteins, comprising alpha casein, beta casein, and kappa casein. They have in common an isoelectric point around pH 4.6. Besides casein, skimmed milk contains a large amount of lactose, the whey proteins among which alpha-lactalbumin and beta-lactoglobulin, certain peptides, salts like calcium phosphate, and several minor components. The beta-casein in breast milk is believed to serve not only as a source of amino acids required for endogenous protein synthesis, but also as an anti-infective agent and an enhancer of calcium absorption. The addition of .beta.-casein as a supplement to infant formula or other nutritional products may, therefore, provide significant health benefits to infants and adults. Beta-casein is believed to enhance calcium absorption by chelating calcium to its phosphorylated residues and thereby keeping it in an absorbable form. Human beta-casein is easily digested by newborn infants and the digestive products have been found to play an important role in the calcium uptake, and thus in the mineralization of the skeleton. A digestion product of human beta-casein has been found to have opioid activity and may be involved in the sleeping patterns of breast-fed infants.

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