1. Separation of Casein

2. Aim
To prepare casein from skimmed milk powder

3. Outcomes
Describe the structure and physicochemical properties of casein
Name the different properties of milk
Explain the nutritional value of casein
Discuss the technical uses of casein and casein products.

4. Milk is the most nutritionally complete food found in nature.
All kinds of milk, human or animal, contain
Vitamins
thiamin,
riboflavin,
pantothenic acid, and
vitamin A,
vitamin B12,
vitamin D,

5. minerals
Carbohydrates
Calcium
principally lactose
potassium,
Lipids (fats)
Sodium,
Triglycerides
phosphorus, and
Saturated fatty acids
trace metals
Cholesterol
Proteins
Phospholipids
mostly casein

6. Casein is a phospho protein
The casein content of milk represents about 80% of milk proteins. Casein is not coagulated by heat. It is precipitated by acids.
Casein is precipitated by simply adjusting the pH of the milk to be sufficiently acidic that the protein is insoluble, taking care not to acidify too much so that the lactose does not hydrolyze.
The isolated casein is insoluble in water, alcohol, and ether.
All the fat can be removed from milk by extraction with petroleum ether or a similar organic solvent.

7. Reagents and glassware
Powdered milk - 5g
Acetic acid (10%) - 5ml
Diethyl ether - 20ml
Ethanol - 20ml
Beakers (100ml)
Plastic dropper
Thermometer
Plastic weighing bowl/boat
Hot plate
Filter paper
Spatula
Wash bottle
Conical flask125ml/250ml
Measuring cylinder
Stirring rod

8. Step 1:
5 grams of powdered dry milk is weighed and dissolved in 20 ml of warm water in a 100 ml beaker.
Temperature of the solution should be maintained at 55oC on a hot plate.

9. Step 2:
10% acetic acid is added drop wise with stirring. (Do not add the acid too rapidly).
Addition of acid is continued (slightly less than 2 ml will be required), keeping the beaker on the hot plate, until the liquid changes from milky to almost clear and the casein no longer separates. (It is important not to add too much acid because it may hydrolyze some of the lactose in the milk and reduce the yield).

10. Step 3:
Casein is placed in a 100 ml beaker and 5 ml of diethylether:ethanol (1:1) mixture is added and stirred for few minutes.
Diethylether:ethanol is decanted and the process is repeated. (The diethylether:ethanol washings remove any small quantities of fat that may have precipitated with the casein).

11. Step 4:
Casein is placed between several layers of filter paper to help dry the product and allowed to stand in the air for minutes.
The product is then placed in a 125 (or 250) ml conical flask containing about 30 ml of water and shaken well.
Casein is then separated from water and washed with ethanol.

12. Step 5:
By using a spatula, the casein is spread on a pre- weighed plastic weighing bowl/boat and allowed to dry over a week.
When dried, the casein product is weighed and the total yield is calculated from the powdered milk.

13. Calculation Weight of the Plastic weighing bowl : A
Weight of the plastic weighing bowl and casein : B
Weight of the casein : B – A g
Result
The total yield of casein in the given milk powder is _______ g

14. Instructions Wash all the glassware provided to your group.
Complete the Lab Exercise and submit after the practicals.
Submission date for your completed assignments of this practical is 18th April 2012