What are the characteristics of milk mixtures?

Do Holstein cows or Jersey cows give more milk?


Read and discuss MILK MIXTURES to explore what happens when milk is homogenized and how milk can be mixed, frozen, separated and heated to make dairy products and dairy recipes.

Complete the activities in INVESTIGATE FOOD CHANGES.


what can happen in a glass of milk

Someone has left a glass of milk out for a few days and it has separated and smells. There are curds or solid chunks in the milk. Could this be cheese?

It’s definitely not! What has happened in this glass of milk is s process called curdling.

The process of curdling all comes down to science. Milk is made up of bunch of different things including fat, protein and sugar, and even has good bacteria in it. Curdling happens when a few of those things interact in the milk.

Here’s what happens:

  • The bacteria starts to get old. If the milk was left in warm place, it increases the speed of this process.
  • That bacteria starts to eat the sugar in the milk. This produces something called lactic acid.
  • The lactic acid causes the protein to clump together.
  • Separation of the liquids and solids occurs. The curdled milk or the lumpy proteins, separate from the liquid, called whey.
  • The production of the lactic acid is also the reason for the smell.

So no, that’s not cheese forming. It’s the protein in the milk floating on the whey, so please do not try to consume it.

However, cheese does get its start in a similar way. A bacteria culture is added to milk, but not the same bacteria you would find in the glass of milk left overnight at home. The bacteria culture causes the solids to separate from the whey. Different processes are then used to make different types of cheese.

Who knew all of this interesting stuff could happen in a simple glass of milk!

safe storage

As milk is perishable, it is important to pay attention to how it is stored.

For example, milk is stored in refrigerators in grocery stores. It’s a good idea to pick up milk last and get it home so it can be stored at a temperature between 0 °C and 4 °C as soon as possible. The milk’s best before date is stamped on all milk products and can help you choose the one with the furthest date.

Once it is opened, milk is safe to consume for up to 3 days. Milk that is bought first should be used first.

Milk can actually pick up odours from other foods, so it’s a good idea to keep milk in its original, closed container. This will maintain its flavour and nutritional value. Did you also know that milk shouldn’t be exposed to light because light can destroy some of its vitamins, like vitamin D and riboflavin.

UHT and canned milk are a bit different. They can be stored in a non-refrigerated area. However, they are also perishable once opened. Opened UHT and canned milk must always be refrigerated. These milk products should be used within 3 days of opening.

Powdered milk can be kept on the shelf for up to six months. Once the package is opened, it has to be used within six months. After the powdered milk is mixed with water to make fluid milk, it should be kept in the refrigerator and used within 3 days.

Milk can also be frozen for up to 6 weeks. It still keeps its flavour and nutritional value. However, it can separate when it is thawed. If it separates, it can be whipped to make it more smooth again.

How many examples of mixtures can you identify in this description?


How many examples can you identify of milk changing its state of matter?


Whipping cream can be a favourite ingredient in many recipes. Check out this video to find out how to make it.

Why does cream whip? What mixtures could you create with whipping cream?


When does whipping cream separate? What dairy product results?