P11 MILK COMPONENTS

OBJECTIVES 

In this practice, we want to observe and reveal the components of milk. Also we want to  know its pH and  the amount of casein. And demonstrate if there are proteins, starch, fats and reducing glucids  in milk.

MATERIAL 

200 mL Beaker

Glacial Acetic Acid

Full-Fat Milk

Wiro Gauze

Lab burner

Watch Glass

A Pipette

Thermometer

Test tube rack

5 test tubes

Iodine solution

Sudan III

Fehling A and Fehling B

Spatula

CuCO4

NaOH (dissolution of 20% in distilled water)

Distilled water

Paper indicators pH

Dropper

PROCEDURE

1.       TO SEPARATE THE CASEIN FROM MILK.

•     Take a beaker of 200 mL and add in fool-fat milk.
•    Then heat the milk in the lab burner and boil it until the milk reaches 40 degrees.
•    Afterwards, prepare dissolution of 1 ml of glacial acetic acid and 10 mL of distilled water.
•     Put a few drops of the solution in the milk.
•   Then, with the help of the strainer, strain the amount of casein and left the serum.

Calculations

We have 200 mL of milk, and the density of its is 1,03 g/ml.  The weight of the casein is 25g.

200 x 1,03 = 206

If we have 25 g of casein in 206 g of milk, which weight of casein will we have in 100 g of milk? 12’1%. (12,1 g of casein in 100 g of milk).

From here all practices are done with the serum.

2.  To know the pH of the milk:

You have to put a paper indicator o pH inside a test tube with the serum of the milk, and it will show you the number of the pH rang ( 1-7 is acid, 8-14 basic). 

3. TO REVEAL THE PROTEINS

• Take a beaker and put 100 mL of distilled water.
• Add in 10mL of the fool-fat milk.
• Then get two drops of the mixture and put it in a test tube.
• Add in 2 mL of the NaOH dissolution and 5 drops of CuCO4.

If the mixture changes to black colour, or similar to purple, we have revealed proteins. 

4. TO REVEAL THE STARCH

Put 2mL of the serum of milk in a test tube, then add 3 drops of Iodine solution in it. There wasn’t a change of colour from yellow to purple that means that there isn’t starch in milk. 

5. TO REVEAL THE FATS

Put 2 mL of the milk serum in a test tube, then add two drops of Sudan III in. If lipids are present the Sudan III  is dissolved, and it turns pink in the whole milk. 

6.  TO REVEAL REDUCING GLUCIDS 

• Put 3 mL of milk serum in a test tube.
• Add 3 drops of Fehling A and another 3 of Fehling B and mix it.
• Take a beaker with distilled water and add the test tube in.
• Warn it until the colour changes.

Results: the colour changed  from blue to brown.

Conclusion:  milk contains lactose that is a reducing glucid because is a discard made of glucose and galactose joined by a monocarbonyl bond.  

RESULTS 

MILK	TEST	RESULT
pH	Paper pH	6 – 7
% casein	Calculate it	12'14 %
Proteins	Test Biuret	+
Starch	Lugol	-
Fats	Sudan III	+
Reducing glucids	Fehling Test	+