4. REQUIREMENTS
● MATERIALS REQUIRED
1.Different sample of milk:
(a) Cow Milk
(b)Buffalo Milk
2. Beakers (100ml)
3. Filter – paper
4. Glass rod
5. Weighing Scale
6. Filtration flask
7. Watch glass
8. Boiling test tube
9. Measuring cylinder
10. Test tube holder
11. Bunsen burner
5. Buffalo Milk Cow Milk
CHEMICALS REQUIRED
a) 1% acetic acid solution
b) Ammonium sulphate solution
6. THEORY
MILK:
●Milk is a opaqua white liquid produced by the mammary glands of mammals .
All mammals,including humans,will normally produce including humans,will normally
produce milk to feed their offspring.
●Since milk is generally viewed as a nutritious food with lots of vitamins,
Minerals, fats, proteins etc. thus used for drinking purpose. Milk is also processed
7. ● However, when it is kept for long time at a temperature of 5 degree it become sour
because of bacteria-LACTO BACILLUS present in air. These bacteria convert lactose
of milk into lactic acid which is sour in teste.
● In acidic condition casein of milk starts separating out as a precipitate.
When the acidity in milk is sufficient and temperature is around 36 degree,
it forms semi-solid mass ,called curd.
● Boiling point of milk: 100.17°C
● Freezing point of milk : For cow and buffalo milk it vary form -0.512 to
-0.572°C & form -0.521 to -0.575°C
● pH: Freshly drawn milk has a pH value in the range of 6.5 to 6.7.
8. ABOUT CASEIN
Casein is the protein which is commonly found in mammalian milk in the
form of calcium caseinate , making up 80% of proteins in cow milk and
between 20% and 45% of the proteins in human milk.
Casein has a wide variety of uses , form being a major component of
cheese , to use as a food additive , to a binder for safety matches. As
a food source , casein supplies for amino acids , carbohydrates and
two inorganic elements , calcium and phosphours.
9. • It has
>relatively little tertiary structure.
>relatively hydrophobic , making it poorly
soluble in water.
It is found in milk as a suspension of particles,
called casein micelles , whose hydrophilic parts
reside at the surface and they are spherical.
The casein’s in the micelles are held together by
calcium ions and hydrophobic interactions.
10. PROCEDURE
1.Take a clear dry beaker put into it 20ml cow’s milks and 20ml of saturated
ammonium suiphate solution slowly and with stirring. Fat along with casein will
precipitate out.
2. Filter the solution and transfer the precipitates in another beaker.
3. Add about 30 ml of water to the precipitate. Only casein dissolves in water forming
milky solution leaving fat undissolved.
4. Heat the milky solution to about 40 C and ad 1% acetic acid solution drop wise,
when casein gets precipitated.
5. Filter the precipitate wash with water and let the precipitate dry.
11. 6. Weight the dry solid mass in a previously weighted watch glass
7. Repeat the experiment with other sample of milk.
→ Dried ppt of cow milk
→ Dried ppt of buffalo milk
12. OBSERVATION
S . No. Type of milk Vol. of milk Weight of Milk
W1gm
Weight of Milk
Casein W2gm
% of casein
1 COW Milk 20ml
2 Buffalo Milk 20ml
13. 1) Volume of milk take in each case =20ml
2) Weight of milk take = W1g
3) Weight of casein isolated = W2g
4) Percentage of casein = Weight of casein ×100
5) Weight of milk
14. CONCLUSION
This study clearly indicated that the amount of casein precipitated
form the buffalo milk was higher than that of the cow milk samples.
“Different samples of milk contain different percentage of casein.”
15. 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 same time for fat and casein to
precipitate out.
5.Take the amount reading carefully with digital weighing
machine only.
+
16. • These micelles have negative charge and on adding
acid to milk negative charge are neutralized.
←
Calcium caseinate + acetic acid → casein(s)+calcium acetate(aq)
