Try this: Lemon butter

Have a fantastic kitchen chemistry experience while making a yummy spread.

You will need

• 300mL carton of cream
• 2 eggs
• 250g white sugar
• juice from 3 lemons
• zest from 2 lemons
• container with lid
• small saucepan
• whisk
• wooden spoon
• stove

What to do

1. Open the container and pour in the cream. Put the lid on tight.
2. Shake the container. Be patient, you'll need to shake for a while.
3. Stop shaking once your cream has separated into solid yellow butter and a liquid residue called buttermilk.
4. Pour off the buttermilk and keep the butter. You can already use this to spread on your toast, but continue on to make it into lemon butter.
5. Whisk eggs and sugar in a saucepan until combined. Don't whisk for too long or your eggs will go stiff.
6. Add butter, lemon juice and zest to saucepan.
7. Stir ingredients over medium heat until it becomes quite thick, like warm honey.
8. Cook for another 2 or 3 minutes. Be careful, don't boil it!
9. Wait for it to cool then put it in a very clean container with the lid on tight (make sure the lid is clean inside too) and refrigerate.

Lemon butter can be a delicious treat but don't eat it too often as it has so much fat and sugar. It is also a fantastic homemade gift.

What's happening?

Cream is an emulsion. Emulsions are colloids, a mixture where tiny drops of liquid are suspended in another liquid. Emulsions are mixtures of two immiscible (unblendable) substances.

When you start out, the fat is distributed through the watery cream. The fat is surrounded by a thin membrane; it is a little globule. The fat globules are like tiny balloons filled with butter instead of air.

When you shake the cream, some of the globules break open. As the tiny butter lumps bump into each other, they stick together.

The lumps of butter get larger and larger, as more and more fat globules are released into the cream. Soon you have a large lump of butter and liquid buttermilk.

The butter you have made consists of butter fat and water. The butter you buy at the shops is about 80 per cent butterfat and 15 per cent water, while the butter you made may have as little as 65 per cent fat and 30 per cent water.

Butterfat is made of chemicals called triglycerides which have three fatty acid groups. Triglycerides are the main component of all animal and vegetable fats.

Butter goes off (becomes rancid) when the butterfat chemicals start to break down. This can release chemicals that taste or smell bad, like butyric acid (CH₃CH₂CH₂COOH) which is also found in parmesan cheese and vomit.

Applications

Emulsions are used in many different ways. They can be found in a range of foods including mayonnaise, some salad dressings, baked goods and confectionary. Egg yolk and mustard are good emulsifiers as they help to mix liquids and keep them as emulsions.

Pharmacists use emulsions to help prepare creams and lotions. Photographers use emulsions to coat their plates, film and paper. Emulsions can also be found in explosives, paints, coatings, make-up and detergents.

• Try another Science by Email activity on emulsions

More information

• Dairy Australia
• The history and making of butter
• Food Science Australia