Casein is a binding protein containing phosphorus and calcium, which is sensitive to acid and precipitates at low pH.
Casein is the main protein in mammals, including cows, sheep and human milk, also known as casein, casein and casein.
α - casein is the main protein of mammals. There is no α - casein in human milk, and β - casein is the main form of casein.Casein is not only a source of amino acids, but also a source of calcium and phosphorus for children. Casein forms curd in the stomach for digestion.[1]
Also called casein, casein, casein, casein, casein, casein, and casein
English: Casein
CAS No.: 9000-71-9
detailed description
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Casein is used by mammals including cows,sheepandpeopleMain ingredients in milkprotein。milkAnd mainly casein,breast milkwithalbuminMainly.Casein is a large, hard, dense, extremely difficult to digest and decomposeCurd（curds）。
Casein ismilkThe highest content of protein in,dental caries, prevention and controlosteoporosisAndrickets, promoteanimalIn Vitro Fertilization, Regulationblood pressure, Treatmentiron-deficiency anemia、Magnesium deficiency neuritisEtcphysiologyEfficacy, especially its promotionConstant element（Ca、Mg）Andtrace element（Fe、Zn、CuCr, Ni, Co, Mn, Se) has the reputation of "mineral carrier" because of its functional characteristics of efficient absorption. It can be used with metalsIons, especiallycalciumIon binding to form solubilitycompoundOn the one hand, it effectively avoids calciumsmall intestineNeutral or microalkaliFormed in sexual environmentprecipitateOn the other hand, it can also make calcium coatedIntestinal parietal cellAbsorption.
Casein is an amorphous, non hygroscopic substance, which can dissolve 0.8-1.2% in water at room temperature. It is slightly soluble in 25 ℃ water and organic solvents, soluble in dilute alkali and concentrated acid, and can absorb water. When immersed in water, it expands rapidly, but the molecules are not combined.
Physicochemical properties
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The isoelectric point of casein is pH4.6[2]Amphoteric protein.It exists in milk in the form of dicalcium phosphate, tricalcium phosphate or a combination of both. Its structure is extremely complex. Until now, there is no completely determined molecular formula, and its molecular weight is about 57000-375000.Casein contains about 3% in milk, accounting for about 80% of milk protein.Pure casein is a white, tasteless, odorless granular solid.The relative density is about 1.26.Insoluble in water and organic solvents.Casein can absorb water, and when immersed in water, it expands rapidly, but the molecules do not bind.
Preparation method
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(1) Fresh milkDegreaseAdd acid (lactic acid, acetic acid, hydrochloric acid or sulfuric acid), adjust the pH to 4.8, so that the casein micelles lose charge and coagulate and precipitate.The casein obtained by this method is called casein, and the casein obtained by adding different kinds of acid is almost the same.Sour casein is white to light yellow powder or particle, slightly with milk odor and sour taste.It only swells in water, and can be dispersed and dissolved in water if ammonia, alkali and their salts are added.Soluble in strong acid, diethanolamine, morpholine, urea, formamide, hot phenol and Turkish red oil.
(2) The crude rennet casein is a white granular, almost tasteless and odorless product, which forms a coagulated precipitate by reacting milk with crude rennet. Heating and burning will produce a unique odor.The ash content of rennet casein is higher than that of casein.
purpose
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Acid casein is mainly used as the base material of coatings, wood, paper and clothadhesive, food additives, etc.As the base material of the coating, it accounts for about half of the total consumption. It has excellent water resistance, can be well dispersed in the pigment and improve the uniformity of the coating.In addition, due to good fluidity and easy coating construction, crude rennet protein is mainly used to make plastic buttons.Compared with other resin buttons, casein buttons have good dyeability, processability and bright color, and the quality is in the middle of the buttons.Casein is mixed evenly with hydrated lime, sodium fluoride and copper sulfate, and then mixed with kerosene to obtain casein glue, which is a kind of adhesive used in aviation industry and wood processing sector.Casein is also used in medicine and biochemical reagents.
Casein is mainly used in the food industry as a nutrition enhancer for solid food, as well as a thickening and emulsifying stabilizer in food processing, and sometimes as a binder, filler and carrier.Casein is especially suitable for cheese, ice cream (dosage 0.3%~0.7%), meat products (such as ham, sausage, dosage 1%~3%) and aquatic meat products in food;Fortify the protein in bread and biscuits with 5% addition;3% in mayonnaise.Because casein is the most perfect protein, it can also be combined with cereal products to make high protein cereal products, elderly food, infant food and diabetes food.[1]
