Thursday, April 1, 2021

Casein proteins

Milk contains both whey and micellar casein protein (~20 and 80% of total protein content, respectively). Casein proteins form large colloidal particles with calcium phosphate to form casein micelles.

The term “micelle” has been applied to the dispersed phase of milk, that is the casein‐ protein complex. The micelles consist of casein molecules, calcium, inorganic phosphate and citrate ions, and have a typical molecular weight of several hundred million.

Casein micelles coagulate in the stomach due to both the acidic environment and the presence of pepsin. However, the micellar casein structure can also be intentionally disrupted by various food processing techniques to modify its functional properties.

Casein micelles are composed of four main types of proteins: αS1‐casein, αS2‐casein, β‐casein, and k‐casein.

Casein precipitates at pH 4.6. About 85% to 90% of casein in bovine milk exists in a colloidal form, known as micelles, which are porous, spherical aggregates with diameters ranging from 50 to 600 nm. Casein contains 0.7–0.9% phosphorus, covalently bound to the protein by a serine ester linkage.

Casein is consequently known as a phospho-protein. All the amino acids that are essential to humans are present in casein in high proportions, with the possible exception of cysteine. Casein may therefore be considered as a highly nutritious protein.
Casein proteins

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