Question

Write a short note on study of casein present in different samples of milk.

Answer 1

Casein is a protein found in milk and other dairy products. Casein in milk is present as calcium caseinate in the form of micelles having negative charge which is because of the reason that milk is slightly acidic in nature with a pH of 6.6.

Complete step by step answer:
We all drink milk and casein constitutes a major portion of its protein. Casein is a family of related phosphoproteins. These proteins are commonly found in mammalian milk, for e.g. they constitute 80% of the proteins in cow’s milk and between 20% and 45% of the proteins in human milk. The most common form of casein is sodium caseinate.
We can say that casein is a source of amino acids, carbohydrates and two essential elements: calcium and phosphorus.
Casein contains a larger number of proline (amino acid) residues, which do not interact. Also there are no disulphide bridges due to which they have relatively little tertiary structure. Casein is hydrophobic in nature thus poorly soluble in water. Casein is found in milk in suspension form, called casein micelles
The isoelectric point of casein is 4.6. Since the pH of milk is 6.6 (slightly acidic), casein has a negative charge in milk. Casein has a wide variety of uses, from being a major component of cheese, to its use as a food additive. It is also used as a type of organic adhesive.
Now, we will study the experiment, how it is performed, what are the requirements to perform the experiment.
So, let us discuss step by step as follows
Experiment here is to study the casein amount present in different samples of milk and comparing them.
For that we will need the following arrangement:
Apparatus and Chemical required:
1.Beakers (250 mL)
2.Conical flask
3.Funnel
4.Measuring cylinder (100 mL)
5.Filter paper
6.Watch glass
7.Acetic acid (LR); 1%
8.Ethanol
9.Glass rods
10.Dropper
11.Different samples of milk
Procedure:
-Take 100 mL of milk samples from each type of milk in separate beakers.
-Heat the sample up to 50-600C and add a few drops of 1% acetic acid solution slowly with the help of a dropper with constant stirring for 5-10 minutes using a glass rod.
-We will observe that Casein will start coagulating in the form of an amorphous solid.
-Now, we will filter the precipitate using funnel and filter paper, wash several times with deionised water.
-Remove the fat by washing it with ethanol. Wash it again using deionised water and let it dry.
-Weigh the dried product in a watch glass.
-Repeat the same procedure for all the samples of milk and compare the casein present in them.

Note:
The cow’s milk in general has a comparatively higher amount of casein than the other milk samples and it is because of this reason cow’s milk is considered to be the healthiest among all. Because casein is a good source of calcium magnesium, carbohydrates and amino acids which are essential for our body functioning and growth.