1. 2014 - 2015
Arpit Ranka
XII – a
Roll No. - 18
2014-2015
Chemistry Investigatory Project
2. ACKNOWLEGEMENT
I would like to express my immense gratitude to my
chemistry teacher Mrs. Poonam Taneja , for the help and
guidance she provided for completing the investigatory
project.
I also thank my parents who gave their ideas and inputs in
making this Project. Most of all I thank our school
management, for providing us the facilities and opportunity
to do this project.
Lastly, I would like to thank my school mates who have
rendered and done this project along with me. Their support
made this project fruitful.
- Arpit Ranka
3. Certificate
This is to certify that Mr. Arpit Ranka (Roll No. - 18) ,
student of class XII – ‘A’, S.D Jain Modern School Surat has
successfully completed research in the below given project
under the heading ‘Study of amount of casein in different
milk samples’ during the academic session 2014-2015 under
the guidance of Mrs. Poonam Taneja.
School Stamp
Signature of Principal
Signature of external examiner
Signature of chemistry teacher
4. Objective –
To study the quantity of Casein present
in different samples of milk.
5. 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:
Casein is the most predominant phosphoprote is found
in milk an cheese. When coagulated with rennet, casein is
sometimes called Paracasein. British terminology, on the
other hand, uses the term caseinogen 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.
SOURCE OF
MILK
WATER
(%)
MINERALS
(%)
PROTEINS
(%)
FATS
(%)
CARBO-HYDRATES
(%)
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
6. 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
micelles which show some resemblance with surfactant-type
micellae 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 micelles
have negative charge and on adding acid to milk the negative
charges are neutralized.
Ca2+
- Caesinate + 2CH3COOH(aq) Casein+(CH3COO)2Ca(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.
7. Applications:
In addition to being consumed in milk, casein in used in
the manufacture of adhesives, binders, protective coatings,
plastics (such as for knife handles and knitting needles),
fabrics, food additives and many other products. It is
commonly used by bodybuilders as a slow-digestive source of
amino acids as opposed to the fast-digesting whey protein,
and also as an extremely high source of glutamine (post
workout). Another reason it is used in bodybuilding, is
because of its anti-catabolic effect, meaning that casein
consumption inhibits protein breakdown in the body. Casein
is frequently found in otherwise nondairy cheese substitutes
to improve consistency especially when melted.
8. Aim –
To study quantity of casein in different samples of milk.
Theory –
Milk contains 3 to 4% casein suspended in water in the
colloidal form. It is precipitated in a weakly acidic medium.
9. Apparatus Required –
Funnel, funnel stand , glass rod , filter paper, weight box ,
test tubes, pestle and mortar.
Chemicals Required –
(i) Different samples of milk.
(ii) Saturated ammonium sulphate solution.
(iii) 1 % acetic acid solution.
10. Procedure –
1. Wash the beaker (250 ml) with the distilled water and dry it.
2.Take20mlofbuffalo’smilkin250mlbeakerandfinditsweight.
3.Add20mlsaturatedsolutionofammoniumsulphateslowlywith
stirring.Fatandcaseinwillseparateoutasprecipitate.
4.Filtertheabovesolutionandtransfertheprecipitateinanother
beaker.
5.Treattheaboveprecipitatewith30mldistilledwater.Casein
dissolvesformingmilkysolutionwhereasfatremainsassuch.
6. Warm the above contents of the beaker to 40 - 45°C on a
low flame. Now, add 1% acetic acid solution drop wise with
stirring when casein gets precipitated.
7. Filter the precipitated casein and wash with distilled water
and dry it.
8. Find the weight of dry precipitate.
9. Repeat the whole experiment with cow’s milk, goat’s milk
and sheep’s milk.
11. Observations –
Volume of milk taken in each case = 20 ml
Weight of milk taken = W₁ g
Weight of Casein isolated = W₂ g
Percentage of casein = Weight of Casein x 100
Weight of milk
S.no. Type of milk Volume of
milk taken
(ml)
Weight
of milk
(W₁ g)
Weight of
Casein
(W₂ g)
Percentage of
casein
1. Buffalo’s
milk
20 23.09 0.632 2.73%
2. Cow’s milk 20 35.66 0.55 1.64%
3. Goat’s milk 20 23.09 0.77 3.67%
12. Result –
Different Samples of milk contains different percentage
of casein.
Highest percentage of casein is present in Goat’s milk.
Precautions –
1. Handle apparatus and chemicals carefully.
2. Add ammonium sulphate solution very slowly.
3. Stir milk while adding chemicals.
4. Do not disturb milk after adding ammonium
sulphate solution and wait some time for fat and
casein to precipitate out.
5. Take the amount readings carefully with digital
weighing machine only.
