Casein

Casein pronounced “kay-seen” in British English, is a family of related phosphoproteins (αS1, αS2, β, κ). These proteins are commonly found in mammalian milk, comprising c. 80% of the proteins in cow’s milk and between 20% and 45% of the proteins in human milk. Sheep and buffalo milk have a higher casein content than other types of milk with human milk having a particularly low casein content.

CAS Number: 9000-71-9

SKU: 1235343642 Category:
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Description

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Casein

CAS Number: 9000-71-9

Casein pronounced “kay-seen” in British English, is a family of related phosphoproteins (αS1, αS2, β, κ). These proteins are commonly found in mammalian milk, comprising c. 80% of the proteins in cow’s milk and between 20% and 45% of the proteins in human milk. Sheep and buffalo milk have a higher casein content than other types of milk with human milk having a particularly low casein content.

Casein has a wide variety of uses, from being a major component of cheese, to use as a food additive. The most common form of casein is sodium caseinate.

As a food source, casein supplies amino acids, carbohydrates, and two essential elements, calcium and phosphorus.

Composition

Casein contains a high number of proline residues, which do not interact. There are also no disulfide bridges. As a result, it has relatively little tertiary structure. 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 only limited resemblance with surfactant-type micelles in a sense that the hydrophilic parts reside at the surface and they are spherical. However, in sharp contrast to surfactant micelles, the interior of a casein micelle is highly hydrated. The caseins in the micelles are held together by calcium ions and hydrophobic interactions.

Any of several molecular models could account for the special conformation of casein in the micelles. One of them proposes the micellar nucleus is formed by several submicelles, the periphery consisting of microvellosities of κ-casein. Another model suggests the nucleus is formed by casein-interlinked fibrils. Finally, the most recent model proposes a double link among the caseins for gelling to take place. All three models consider micelles as colloidal particles formed by casein aggregates wrapped up in soluble κ-casein molecules.

The isoelectric point of casein is 4.6. Since milk’s pH is 6.6, casein has a negative charge in milk. 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 aqueous sodium oxalate and sodium acetate.

The enzyme trypsin can hydrolyze a phosphate-containing peptone. It is used to form a type of organic adhesive.

Uses

Food

Several foods, creamers, and toppings all contain a variety of caseinates. Sodium caseinate acts as a greater food additive for stabilizing processed foods, however companies could opt to use calcium caseinate to increase calcium content and decrease sodium levels in their products.

Caseinate Presence and Function in Different Products
ProductCaseinate %Function
Meat2–20Texture and nutrition
Cheese3–28Matrix formation, fat, and water binding
Ice Cream1–7Texture and stabilizer
Whipped toppings2–11Fat stabilization
Pasta2–18Texture, nutrition, and taste
Baked goods1–15Water binding

The main food uses of casein are for powders requiring rapid dispersion into water, ranging from coffee creamers to instant cream soups. Mead Johnson introduced a product in the early 1920s named Casec to ease gastrointestinal disorders and infant digestive problems which were a common cause of death in children at that time. It is believed to neutralize capsaicin, the active (hot) ingredient of peppers, jalapeños, habaneros, and other chili peppers.

Cheesemaking

Cheese consists of proteins and fat from milk, usually the milk of cows, buffalo, goats, or sheep. It is produced by coagulation that is caused by destabilization of the casein micelle, which begins the processes of fractionation and selective concentration. Typically, the milk is acidified and then coagulated by the addition of rennet, containing a proteolytic enzyme known as rennin; traditionally obtained from the stomachs of calves, but currently produced more often from genetically modified microorganisms. The solids are then separated and pressed into final form.

Unlike many proteins, casein is not coagulated by heat. During the process of clotting, milk-clotting proteases act on the soluble portion of the caseins, κ-casein, thus originating an unstable micellar state that results in clot formation. When coagulated with chymosin, casein is sometimes called paracasein. Chymosin (EC 3.4.23.4) is an aspartic protease that specifically hydrolyzes the peptide bond in Phe105-Met106 of κ-casein, and is considered to be the most efficient protease for the cheese-making industry (Rao et al., 1998). British terminology, on the other hand, uses the term caseinogen for the uncoagulated protein and casein for the coagulated protein. As it exists in milk, it is a salt of calcium.

PRODUCT DESCRIPTION: Casein pronounced "kay-seen" in British English, is a family of related phosphoproteins (αS1, αS2, β, κ). These proteins are commonly found in mammalian milk, comprising c. 80% of the proteins in cow's milk and between 20% and 45% of the proteins in human milk. Sheep and buffalo milk have a higher casein content than other types of milk with human milk having a particularly low casein content.

Product Name: Casein

CAS number: 7632-00-0

Product Specification