Caesin Present In Different Samples Of Milk – Chemistry Project

 

S.No.		Contents	II	Page No.
I.		Introduction
II.		Requirements
III.		Theory
IV.		Procedure
V.		Observation
VI.		Conclusion
VII.		Bibliography

Introduction

Milk is a complete diet as it contains in its Minerals, Vitamins, Proteins, Carbohydrates, Fats And Water. Average composition of milk from different sources is given below:

Source	Water	Mineral		Protein	Fats	Carbohydrate
of milk	(%)	s (%)		ns(%)	(%)	(%)
Cow	87.1	0.7		3.4	3.9	4.9
Human	87.4	0.2		1.4	4.0	4.9
Goat	87.0	0.7		3.3	4.2	4.8
Sheep	82.6	0.9		5.5	6.5	4.5

Casein is a major protein constituent in milk & is a mixed phosphor-protein. Casein has isoelectric pH of about 4.7 and can be easily separated around this isoelectric pH. It readily dissolves in dilute acids and alkalis. Casein is present in milk as calcium caseinate in the form of micelles. These micelles have negative charge and on adding acid to milk the negative charges are neutralized.

Ca²+-Caseinate +2CH₃COOH(aq)-Caesin+(CH₃COO)₂Ca

REQUIREMENTS

>                 Beakers (250 ml)

>                 Filter-paper

>                 Glass rod

>                 Weight box

>                 Filtration flask

>                 Buchner funnel

>                 Test tubes

>                 Porcelain dish

>                 Different samples of milk

>                 1 % acetic acid solution

>                 Ammonium sulphate solution

Theory

Natural milk is an opaque white fluid. Secreted by the mammary glands of female mammal . The main constituents of natural milk are Protein, Carbohydrate, Mineral, Vitamins, Fats and Water and is a complete balanced diet. Fresh milk is sweetish in taste. However, when it is kept for long time at a temperature of 5 degree it becomes sour because of bacteria present in air . These bacteria convert lactose of milk into lactic acid which is sour in taste.    In acidic condition casein of milk starts separating out as a precipitate. When the acidity in milk is sufficient and the temperature is around 36 degree, it forms a semi-solid mass, called curd.

PROCEDURE

1. A clean dry beaker has been taken, followed by putting 20 ml of cow’s milk into it and adding 20 ml of saturated ammonium sulphate solution slowly and with stirring. Fat along with Caesin was precipitate out.

2. The solution was filtered and transferred the precipitates in another beaker. Added about 30 ml of water to the precipitate. Only Caesin dissolves in water forming milky solution leaving fat undissolved.

3. The milky solution was heated to about 40^oC and add 1% acetic acid solution drop-wise, when casein got precipitated.

4. Filtered the precipitate, washed with water and the precipitate was allowed to dry.

5. Weighed the dry solid mass in a previously weighed watch glass.

6. The experiment was repeated with other samples of milk.

OBSERVATIONS

CONCLUSION

Different samples of milk contain different percentage of Caesin.

BIBLIOGRAPHY

• NCERT CHEMISTRY XII
• ENCARTA ENCYCLOPEDIA 2009

You can find other Chemistry Projects here.