This activity is from CSIRO’s free weekly e-newsletter Science by Email.  Each issue includes science news, a hands-on activity to do at home, a quiz and more. Visit www.csiro.au/sciencemail to subscribe. Want more hands-on activities? Visit CSIRO’s DIY Science pages and the Science by Email activity archive

Warning: this activity requires the use of a hot stove. Younger scientists should ask an adult for help. Be careful not to burn yourself!

You will need

• 2 litres of milk
• 1/3 cup of lemon juice
• large pot with lid
• thermometer
• wooden spoon
• colander
• cheese cloth
• string
• fresh herbs, salt and pepper (optional)

What to do

1. Heat the milk to 80 degrees Celsius in a pot on the stove and then turn off the hotplate. Make sure that you stir the milk while heating to stop it from burning and even for a short while after you have turned the heat off.
2. Add your lemon juice and stir well.	Pour the milk into the pot, carefully heat it to 80 degrees Celsius, then add lemon juice.
3. Put the lid on your pot. Let the mixture set for 15 minutes until the mixture separates into curds and whey. If the liquid (the whey) is still milky, add more lemon juice.
4. Line a colander with cheese cloth, then pour in the lumpy curds.	Once the curds have separated from the whey, strain the mixture using cheese cloth.
5. Tie the corners of the cheese cloth together. Hang the parcel to drain for 1-2 hours.	Tie the cheese cloth together and drain, allowing all the liquid whey to run out.
6. Remove the cheese. If you want to, add salt, pepper and herbs. Your cheese is ready to eat!	Add salt, pepper and herbs to taste. Enjoy!

Store your cheese in a sealed container in the fridge for up to a week.

What’s happening?

In this activity, you separated milk into curds and whey. This is the main step required to make any sort of cheese.

You’ve probably heard of curds and whey before, in the nursery rhyme Little Miss Muffet. Before being interrupted by a very rude spider, Miss Muffet was sitting down to a bowl of lumpy cheese and liquid, similar to what you have just made.

Milk has lots of protein in it. The lemon juice you added caused the proteins in the milk to become separated. The clumpy curds that become cheese are made from the milk protein, casein. Other cheeses are curdled by vinegar, or more typically by the addition of bacteria and an enzyme – a chemical to help the process – called rennet.

So, what is the difference between different types of cheese? There are lots of different milks that can be used for different flavours. This includes cow, goat, sheep and buffalo milk.

Some types of cheeses also have different bacteria added. These bacteria may require different temperatures and grow at different rates. In addition, mould may be added, or herbs, or smoke.

There are lots of different factors that come into play when making cheese, which is why there are so many yummy types!

Try another dairy-based Science by Email activity.

More information

Podcast: listen to a cheese researcher
In the cheese lab
Study cheese at Charles Sturt University

This article is an initiative by CSIRO Education