Last week the Fun Friday blog was all about density, how less dense liquids will sit on top of more dense liquids and how some liquids such as oil and water do not mix!
Milk and cream are quite like the oil and water mix as they are made up of fat and water. So why do they not separate into two layers like the oil and water we used last week? That is because the fat is broken up into tiny little droplets that float evenly throughout the water. This is an example of an
emulsion.
For today's Fun Friday we separated the fat from the water in cream and made some yummy butter! My Fun Friday Science Team really enjoyed this experiment especially as they got to eat the results... spread thick on their favourite bread!
How to make butter...
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What you will need: double cream, salt (optional) a jar with a screw tight lid (preferable plastic!) and a
marble (optional) |
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| Add the marble (if using) and the cream to the jar (no more than half full). |
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| Add salt (if using) ... we used about half a teaspoon. |
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| Put the lid on tight and start shaking.... |
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| ....And shaking.... |
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| ...And shaking! |
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| First it turned to whipped cream, then small lumps of butter started to form! |
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Keep shaking (about 10-15 minutes) until the butter lumps start to get bigger and clump together
and you can see the watery bit separate out. |
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At this stage you can stop shaking (phew!); now you want to separate the butter from the watery bit
(which is actually buttermilk!). |
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We used clean muslin to separate the butter from the buttermilk, but a few sheets of
kitchen roll will work too, or even a clean tea towel. |
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| Squeeze the lump of butter to remove more of the liquid! |
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Et voila! You end up with a lovely yellowy lump of butter and some buttermilk
(we used our buttermilk for making bread!)
You can add salt at this stage instead if you prefer! |
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| We made this! |
So what happened (the science bit!)?...
As I mentioned the cream is an emulsion.... a liquid suspension of tiny droplets of one liquid floating in another liquid. In this case tiny droplets of milk fats float in mainly water. When we shake the mixture the tiny droplets of fat collide with each other and the fat sticks together. If we keep mixing most or all of the fat will stick together in one big lump, completely separated from the water. The resulting lump of milk fats is our butter!
This was a really fun and simple experiment that made my kids think about the science behind their food and where it comes from. It has started a number of discussions in our home and no doubt will lead to a few more posts on this blog! Of course once we had made the butter I had to make some yummy bread to put it on and now the kids want me to make the blackberry jam from our stash in the freezer. :)
Enjoy your weekend!
If you try out this experiment or have any questions or things to add, do please leave a comment below, we love to hear from you!
Labels: butter, cream, density, Dr. How's Science Wows, emulsion, fat droplets, kids, milk, science