Once milk comes out of the cow’s body it need to be handled very carefully. Milk left at room temperature will start to grow bacteria within two days.

To prevent any unwanted bacteria from growing, milk must either be heated to destroy them, or cooled to slow down their movements. The process of heating and then cooling milk is called pasteurisation. French doctor and scientist Louis Pasteur invented the process of pasteurisation more than a century ago. Since its discovery, pasteurisation has safeguarded much of our food supply, including milk and dairy products.

The milk is heated to 70 – 75 degrees centigrade and then rapidly chilled again to 4 degrees. The heat destroys most bacteria and the rapid cooling process prevents the remaining bacteria from multiplying. It also destroys any organisms (bacteria or viruses) that could cause illness. Pasteurisation has practically no effect on the taste or nutritional value of the milk.

	What are bacteria?
	Bacteria are tiny living organisms that occur everywhere. They are so tiny you cannot see them without a microscope. Bacteria may be harmful, or good for milk.

Tip: Always put the milk back in the fridge when you have used it.

Ultra High Temperature (UHT)

This is a form of pasteurisation. As the name suggests this milk is subject to extremely high temperatures (140 degrees). This lasts for 2-4 seconds. It is then immediately cooled. Almost all bacteria are destroyed in the process and the milk can be kept for months without refrigeration in its sealed packaging.

If you do not see a layer of cream at the top of a bottle of milk, this does not mean there is no cream in the milk. Because butterfat is lighter than the rest of the milk, it rises to the top and forms a layer of cream. To prevent this milk is homogenised. In the process the milk is forced through tiny holes under high pressure. This breaks the fat and distributes it evenly throughout the milk. Homogenised milk has a creamy taste and it whiter than before.