Procedure:

 

• Weigh 4.0 ± 0.1 g of ammonium sulfate into a 50 mL conical flask.

 

• Using a measuring cylinder, add 20 ± 0.5 ml of the milk sample into the conical flask.

 

• Shake the flask for 1 min to ensure dissolution of ammonium sulfate. Allow the mixture to stand for a period of not less than 5 min.

 

• Filter through a folded filter paper into a test-tube marked at 5 ml prior to filtration.

 

• After collecting a minimum of 5 ml of clear filtrate, place the test-tube in a beaker of boiling water which is kept boiling for at least 5 min (or heated water bath at maximum temperature for at least 10 min).

 

• Transfer the test-tube to a beaker of cold water to let cool and examine the contents for evidence of turbidity (i.e. cloudiness). Milk that has been properly sterilised will show no sign of turbidity (i.e. remains clear).

 

ATTENTION:

 

• Ensure no spillage of ammonium sulfate during weighing and when pouring into the 50 ml conical flask.

 

• Ensure thorough mixing to ensure all ammonium sulfate has dissolved into the milk.

 

• Ensure proper filtration.

 

• Ensure that the water is boiling before placing the test-tube inside the boiling water and before starting the stopwatch for 5 min.

 

• Do not throw the filtrate after filtration as you can use it to compare the difference before and after boiling.