Chemistry Project to Study the Quantity of Caesin in Milk
Study of Quantity of Caesin Present in Different Samples of Milk
Name: Bharat Jain
School: Aditya Birla Public School, Kovaya, Gujarat
Department: Chemistry
Academic Year: 2009-2010
Acknowledgement
I wish to express my deep gratitude and sincere thanks to the Principal, Raji Jayaprasad, Aditya Birla Public School, Kovaya, for her encouragement and for all the facilities that she provided for this project work. I sincerely appreciate this magnanimity by taking me into her fold for which I shall remain indebted to her.
I extend my hearty thanks to Mr. B.D. Kotwani, chemistry teacher, who guided me to the successful completion of this project. I take this opportunity to express my deep sense of gratitude for his invaluable guidance, constant encouragement, constructive comments, sympathetic attitude and immense motivation, which has sustained my efforts at all stages of this project work.
I can’t forget to offer my sincere thanks to Mr. Pankaj Bajpayee and also to my classmates who helped me to carry out this project work successfully and for their valuable advice and support, which I received from them time to time.
Bharat Jain
Declaration
I do hereby declare that this project work has been originally carried under the guidance and supervision of Mr. B.D. Kotwani, Head of Chemistry Department, Aditya Birla Public School, Kovaya.
Bharat Jain
Introduction
Milk is a complete diet as it contains minerals, vitamins, proteins, carbohydrates, fats, and water. Average composition of milk from different sources is given below:
| Source of Milk | Water (%) | Minerals (%) | Proteins (%) | Fats (%) | Carbohydrates (%) |
|---|---|---|---|---|---|
| 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 |
Caesin is a major protein constituent in milk and is a mixed phospho-protein. Casein has an isoelectric pH of about 4.7 and can be easily separated around this isoelectric pH. It readily dissolves in dilute acids and alkalies. Casein is present in milk as calcium caseinate in the form of micelles. These micelles have a negative charge and on adding acid to milk the negative charges are neutralized.
Ca²⁺-Caesinate + 2CH₃COOH(aq) → Caesin + (CH₃COO)₂Ca
Aim
Aim: To study the quantity of casein in different samples of milk.
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 mammals. The main constituents of natural milk are protein, carbohydrate, minerals, vitamins, fats, and water, and it is a complete balanced diet. Fresh milk is sweetish in taste. However, when it is kept for a long time at a temperature of 5°C 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 temperature is around 36°C, it forms a semi-solid mass called curd.
Procedure
- A clean dry beaker was 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 precipitated out.
- The solution was filtered and the precipitate was transferred to another beaker. About 30 ml of water was added to the precipitate. Only caesin dissolves in water, forming a milky solution, leaving fat undissolved.
- The milky solution was heated to about 40°C and 1% acetic acid solution was added drop-wise, whereupon casein precipitated.
- The precipitate was filtered and washed with water, then allowed to dry.
- The dry solid mass was weighed in a previously weighed watch glass.
- The experiment was repeated with other samples of milk.
Observations
Different samples of milk contain different percentages of caesin.
Conclusion
Different samples of milk contain different quantities of caesin.
References
- Comprehensive Practical Chemistry; Laxmi Publications.