Chemistry Project
Project Work of Chemistry
Academic Year : 2079-2080
Department : Science
Name of Assignment: Study the presence of casein in different samples
of milk
Student’s Name : xxxxx xxxx
Section : D
Subject : Chemistry
Date of Submission :
……………………… Teacher’s Signature
CERTIFICATE
This is to certify that Mr. Xxxx xxxxi has completed his chemistry project entitled “STUDY OF CASEIN PRESENT IN DIFFERENT SAMPLES OF MILK”
Himself and under my guidance during the academic year 2079-2080. The progress of the report has been in my knowledge consistently.
…………………… …..…………….
Teacher’s Signature Head of institution
ACKNOWLEDGEMENT
I would like to express special thanks of gratitude to our chemistry teacher MrABC Khanal as well as Department of Chemistry Kalika Manavgyan Secondary School who gave us the golden opportunity to do this wonderful project of studying casein present in different samples of milk.Without his motivation and help the successful completion of this project would not have been possible.
Lastly, I would like thank my schoolmates who have rendered and done this project along with me. Their support made this project fruitful.
- XXX XXX
-12 ‘D’
OBJECTIVE
TO STUDY THE QUANTITY OF CASEIN PRESENT IN DIFFERENT SAMPLES OF MILK
INDEX
Introduction
Theory
Requirements
Procedure
Observation
Conclusions
Bibliography
INTRODUCTION
Milk is a complete diet as it contains proteins, carbohydrates, fats, minerals, vitamins and water. The 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 0.7 3.3 4.2 4.8
Sheep 82.6 0.9 5.5 6.5 4.5
Casein is the most predominant phosphoprote is found in milk and cheese. When coagulated with rennet, casein is sometimes called paracasein. British terminology, on the other hand, uses the term casenogen for the uncoagulated protein and casein for coagulated protein. As it exists in milk, it is a salt of calcium.
Casein is not coagulated by heat. It is precipitated by acids and by rennet enzymes, a proteolytic enzyme typically obtained from the stomachs of calves. The enzyme trypsin can hydrolyze off a phosphate-containing peptone………(1)
( I )
Casein consists of a fairly high number of praline peptides which do not interact. There are also no disulphide bridges. As a result, it has relatively little secondary structure or tertiary structure. Because of this, it cannot denature. It is relatively hydrophobic, making it poorly soluble in water. It is found in milk as a suspension of particles called casein miscelles which show some resemblance with surfactant-type miscellae in a sense that the hydrophilic parts reside at the surface. The caseins in the micelles are held together by calcium ions and hydrophobic interactions. These miscelles have neagative charge andon adding acid to milk the negative charges are neutralized……….(1)
〖Ca〗^(2+)-Caesinate+2〖CH〗_3 COOH→Casein+(〖CH〗_3 COO)_2 Ca(aq)
The isoelectric point of casein is 4.7. The purified protein is water insoluble. While it is also insoluble in neutral salt solutions, it is readily dispersible in dilute alkalis and in salt solutions such as sodium oxalate and sodium acetate……….(2)
Fig: Isolation of casein from Milk………(5)
( II )
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 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 late lactic acid which is sour in taste. In acidic condition casein of milk starts separating out as a precipitate when the acidity in the milk is sufficient and temperature around 36 degree. It forms semisolid mass called curd……..(3)
Milk components
Fig: Milk components………….(4)
( III )
REQUIREMENTS
Beakers (250ml )
Filter paper
Filtration flask
Test tubes
Porcelain dish
Spatula
Glass rods
Dropper
Weight bore
Different samples of milk
10% acetic acid
Diethyl ether and ethanol
( IV )
PROCEDURE
A clean dry beaker had been taken followed by putting 20 ml of cow’s milk into it and weight was taken.
The milky solution was heated to about 40°C and added 10% acetic acid solution drop wise with stirring when casein gets precipitated.
The above solution was filtered and the casein precipitated was taken out.
The precipitated casein was again transferred to 50 ml mixture of diethyl ether and ethanol in the ratio of 1:1. The solution was mixed properly with glass rod.
Again the mixture was filtered to separate the casein from solvent mixture and casein was collected.
The casein was transferred to dish and kept it for drying.
Weighted the dry solid mass and calculate the percentage composition.
The experiment was repeated with other samples of milk.
( V )
OBSERVATIONS
Volume of milk taken in each case = 20 ml
Weight of milk taken = W_1g
Weight of casein taken = W_2g
Percentage of casein = (Weight of casein)/(weight of milk ) ×100%
S.N Type of Milk Volume of milk taken (ml) Weight of milk (W_1g) Weight of casein (W_2g) Percentage of casein
1. Cow milk 20 21.3g 0.63g 3%
2. Goat milk 20 20.92g 0.68g 3.25%
3. Buffalo milk 20 20.23g 0.85g 5.2%
( VI )
CONCLUSION
Different samples of milk contain different quantity of casein. Buffalo milk contain the highest quantity of casein than goat and cow milk while, cow milk contain the lowest quantity of casein.
( VII )
PRECAUTIONS
Milky solutions should not be over heated.
Precipitate should filtered properly.
Different samples of milk should be taken.
Apparatus should used carefully.
( VIII )
Bibliography
1. www.caesine-pro.com
2. www.wikipedia.com
3. www.chymist.com
4. www.onlinelibrarywiley.com
5. www.scientificamerican.com
The report is not plagiarized and the related information from the source is clearly mentioned.
( IX )
Some pictures taken while doing the project work
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