Question

To determine the amount of casein in different samples of milk

Answer 1

Answer:

Explanation:

TO STUDY THE QUANTITY OF CASEIN PRESENT IN DIFFERENT SAMPLES OF MILK

OBJECTIVE:

 

MATERIALS REQUIRED:

• Beakers (250 ml)  
• Filter-paper  
• Glass-rod
•  Weighing machine
•  Filtration-flask
• Funnel
• Test-tubes
• Burner
• Different samples of Milk
• 1% acetic acid solution
• Saturated ammonium sulphate solution.

PROCEDURE:  

• Take a clean dry beaker, put into it 20mL of sample milk and add 20 ml of saturated ammonium sulphate solution slowly and with stirring. Fat along with casein will precipitate out.

• Filter the solution and transfer the precipitates in another beaker.
•  Add about 30 ml of water to the precipitate.
•  Only casein dissolves in water forming milky solution leaving fat undissolved.
• Heat the milky solution to about 40°C and add 1% acetic acid solution drop wise,   when casein gets precipitated.
• Filter the ppt., wash with water, and let the ppt. dry.
• Weigh the dry solid mass in a previously weighed watch glass.
• Repeat the experiment with other samples of milk.

Calcium caseinate  +  2CH3COOH(aq) →  Casein(s)  + (CH3 COO) 2 Ca (aq)

OBSERVATIONS AND CALCULATION:

Volume of milk taken in each case = 20 ml  

% of Casein  =  Weight of Casein /  Volume of milk taken *100