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Casein is the chief protein component present in mammalian milk. It is available for consumption in two major forms namely micellar caseins and casein hydrolysates.
- Milk is composed of two main proteins, namely Casein and Whey.
- 80% of the milk is casein while the rest 20% is whey.
- It is generally a tasteless and odorless white amorphous solid in nature.
- Commercially used caseins have a yellowish color and pleasant odor.
- The main component used for the manufacturing of caseins is skim milk.
The applications of casein include paints, leather, glues, plastics, medicinal supplements, textiles, paper coatings, etc. It is an essential ingredient in the cheese-making process.
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Key Terms: Casein, Protein, Micellar Caseins, Milk, Casein Hydrolysate, Amorphous Solids, Cheese, Casein Protein
What are Caseins?
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Caseins are odorless and tasteless protein components present in milk and constitute 80% of it.
- Casein belongs to the family of phosphoproteins and is mainly found in mammalian milk.
- It acts as a supplier of carbohydrates, amino acids, calcium, and phosphates.
- Casein has applications in a wide range of industries of pharmaceutical, textiles, leather, paper, and food.
Casein
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Forms of Casein
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The two major forms of caseins available for consumption are:
- Micellar Caseins
- Casein Hydrolysate
Micellar caseins are the most common natural form of casein. They undergo phase separation to form colloidal particles of tiny structures called micelles. They clot in the stomach and thus slow down absorption. Calcium hydrolysates are the partially broken and hydrolyzed form of the casein protein. These quicken the absorption process and thus exhibit easy digestion.
Properties of Casein
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The major physical and chemical properties of casein are as follows:
- Casein in its pure form is a white amorphous solid which is odorless and tasteless in nature.
- Commercial casein is yellowish in color and has a pleasant odor in nature.
- Dry casein is in a well-stable condition and is protected from the attacks of rodents and insects.
- When it is damp, it gives out a bad odor and is in danger of attacks by rodents and insects.
- Casein shows isoelectric nature at a pH of 4.6, where its solubility with water is 0.01%.
- It forms moderately soluble salts like casein chloride at a pH below 4.6
- It forms salts with bases like sodium caseinate and calcium caseinate at a pH above 4.6.
- Casein is a lyophilic colloid and is amphoteric in nature.
- It forms gels upon the slow coagulation with the concentrated solutions.
- Upon mixture with formaldehyde, caseins form insoluble compounds.
Casein and Whey Protein
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Manufacturing of Casein
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The major three methods of manufacturing the casein protein are as follows:
- The precipitation of acid casein can be done by the addition of dilute hydrochloric acid/ dilute sulphuric acid into the skim milk.
- The skim milk is fermented by the Streptococcus lactisi bacterium producing enough lactic acid, out of which the casein protein is then curdled out.
- The rennet casein is formed by setting rennet extract with warm skim milk until the clotting of calcium paracaseinate happens. The clot is then cut into smaller pieces and then the whey is allowed to dry.
After the caseins are processed by the above methods, the whey is dried, washed with water, drained, pressed, and dried in air. They are then grounded and packed for sale once the manufacturing is over.
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Uses of Casein
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Casein has a wide range of applications in various industries.
- Pigmented Caseins act as paper coatings for books and art papers by providing the appropriate surface for illustrations.
- Casein Glue is used as wood joints and it is composed of the acid casein lime, fungicide, and the suitable salts of sodium.
- Casein Paints are used for decorations on interior and exterior walls. Casein paint gives a lustreless and washable paint decoration and is commercially available in powdered form.
- Casein Plastics have a variety of applications some of which are beads, buttons, knitting needles, fountain pens, cutlery and umbrella handles, etc.
- Other applications of casein include uses in medicine supplements, dietary supplements, packaged foods, textiles, and cosmetics.
- They are also used for leather dressing, textile printing, textile sizing, soapmaking, shoe polishes, shoe cleaners, insecticide sprays, etc.
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Things to Remember
- Casein is the major protein component of mammalian milk and is a necessary ingredient in making cheese.
- Pure caseins are tasteless, odorless, white amorphous solids while commercial caseins are yellowish and have a pleasant odor.
- Skim milk is the major component used in all the methods of casein manufacturing.
- The two forms of caseins are micellar caseins and casein hydrolysates.
- Casein proteins constitute about 80% of milk while whey proteins constitute 20% of it.
- The uses of casein include paper coatings, glue, plastic, dietary supplements, paints, medicine supplements, textiles, and cosmetics.
Sample Questions
Ques. Mention three uses of casein protein. (3 Marks)
Ans. Casein proteins have the following uses:
- The pigmented caseins are used as paper coatings for books, art papers, and envelopes. These casein-coated pigmented surfaces are suitable for creating suitable half-tone illustrations.
- Casein glues are used for wood joints.
- Casein paints are used for painting the exterior and interior walls to give lusterless and washable decorations.
- They are also used in making the leather dressing, plastics, shoe polishes, insecticides, etc.
Ques. Describe the two major forms of caseins based on food consumption. (3 Marks)
Ans. The two major forms of caseins based on food consumption are:
- Micellar Caseins: They are formed when caseins undergo phase separation to form tiny colloidal structures called micelles. These micellar caseins clot in the stomach and thus slow down the process of absorption.
- Casein Hydrolysate: They are the partially broken and hydrolyzed form of casein. They quicken the absorption process and thus exhibit easy digestion.
Ques. How are casein proteins different from whey proteins? (2 Marks)
Ans. The composition of casein proteins in milk is 80% while whey protein is only 20%. Casein proteins exhibit a slower rate of absorption and digestion while whey proteins exhibit quicker digestion. The two major forms of whey proteins used as supplements are whey isolate and whey concentrate while the two major forms of casein proteins are micellar caseins and casein hydrolysates.
Ques. Write any five properties of casein. (3 Marks)
Ans. The following are the properties of casein:
- It is a white amorphous solid which is odorless and tasteless in nature.
- It is a lyophilic colloid that is amphoteric in nature.
- The specific gravity of the casein protein ranges between 1.25 and 1.31.
- Gels are formed by casein on slow coagulation with the concentrated solutions.
- When the casein is dry, it is in a well-stable condition while when the casein is damp, it gives out a bad odor and is in danger of the attacks of rodents and insects.
Ques. How are rennet caseins formed? (2 Marks)
Ans. The rennet caseins are formed by setting rennet extract with warm skim milk until the clotting of calcium paracaseinate happens. The clot is then cut into smaller pieces and then the whey is allowed to dry.
Ques. What are whey proteins? What is its composition in milk? (2 Marks)
Ans. Whey proteins are one of the protein constituents present in milk along with caseins. They are also the byproduct of the cheese-making process. The whey protein is about 20% of the total protein composition of mammalian milk.
Ques. Why are dry caseins better than damp caseins? (2 Marks)
Ans. Dry caseins are better than damp caseins because dry caseins are well conditioned and thus protected from rodents and insects. In the case of damp caseins, they produce a bad odor and are more prone to attacks from rodents and insects.
Ques. How are casein plastics made? (3 Marks)
Ans. The rennet caseins are first granulated and then water is added to moisten them. The moistened form is kneaded thoroughly and the addition of dyes/ pigments takes place. The absorption of water by the granules softens the mixture. Then this softened mixture is passed through a heated cylinder press and is thrust out through tubes and pipes under pressure as soft plastic.
This soft plastic is then molded into the desired shape and is hardened by soaking in a formaldehyde solution for a long duration. After the hardening process, they are slowly dried, and thus, casein plastics are made.
Ques. Explain the nature of casein-based on its pH level. (3 Marks)
Ans. The nature of casein and its properties varies based on its pH level:
- When the casein pH is 4.6, it shows isoelectric nature and is soluble in water with a solubility of 0.01%.
- When the pH is below 4.6, casein forms moderately soluble salts like casein chloride.
- When the pH is above 4.6, caseins form salts with bases.
- Sodium caseinates are soluble completely while calcium caseinates are nearly insoluble in water.
Ques. What are the three methods to manufacture caseins? (3 Marks)
Ans. The major three methods of manufacturing caseins are as follows:
- With the help of bacteria named Streptococcus lactose, milk is fermented which leads to the formation of lactic acid. It then leads to the natural sourcing of casein curdles once enough lactic acid is formed.
- Casein is also formed by the addition of sulfuric acid or hydrochloric acid to precipitate acid casein.
- For rennet casein, the setting of warm skim milk is done with the help of rennet extract till the time clotting of calcium para caseinate takes place. After this, the clot is further cut into small parts, thus allowing the whey to drain off.
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