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Making Butter Experiment #435
Grade Level(s): 1-2, 3-5, 6-8
By: Robert Krampf

This week's experiment came from a conversation that I had with my sister. We were talking about all the inventions and discoveries that have happened during my Grandmother's 100 years, and how much daily life has changed. She commented that she has her students make butter in the classroom, so they would understand where it comes from. I knew that I had another experiment.

Materials:

To try this delicious treat, you will need:
a small container of heavy whipping cream
a glass jar with a tight fitting lid

Plan:

If you have never made butter, these instructions may sound strange, but trust me, it works wonderfully. The first thing to do is to let the cream sit on the counter, at room temperature, for about 12 hours. I put it out on the counter after supper, and I had freshly made butter on my toast the next morning.

After letting the cream sit, pour it into the glass jar. Don't worry if it has a slightly sour smell. Put the lid on the jar. Now we have to shake the jar, but we don't want to just start shaking it wildly. We want to watch what is happening. Give it one good hard shake about once every second. Watch carefully. For the first few minutes, not much will happen. Then suddenly, you will feel something solid hit the jar when you shake it. Look inside and you will see a large lump of butter. Give it a few more hard jolts and your butter should be ready.

Open the jar and look carefully. Around the butter is a thin, white liquid, which is commonly known as buttermilk. If you have ever had buttermilk biscuits, this is what they are made with. Pour off the buttermilk and add some cold water to the jar. Swirl it around a bit and then pour it off. Repeat this a few times, until the water remains clear. Drain all the water and put the lump of butter into a small bowl.

At this point, you have sweet cream butter, which is wonderful on hot bread or fresh biscuits. If you prefer salted butter, simply sprinkle some salt into the butter and stir it in. At this point, treat the butter just as you would the butter you get from the store.

That was quite yummy, but how and why did it work? First, we have to know a bit about milk. If you have ever been lucky enough to have milk fresh from the cow, you know that if you let it sit for a while, the cream floats to the top. That is because milk contains lots of tiny globules of milk fat, each surrounded by a thin membrane. Imagine tiny balloons filled with butter instead of air. Because the milk fat (butter) is lighter than the liquid, they tend to float. The cream that rises to the top is really a very high concentration of these fat globules floating on the milk. The milk from the grocery does not do this because it has been homogenized, a process that makes the fat globules small enough to keep them mixed evenly in the milk.

We left the cream out of the refrigerator overnight for two reasons. First, it helps the fat in the globules to form crystals. These crystals will help to break the membrane when we shake the cream. Imagine a water balloon with shards of glass inside. One jolt would cause the glass to slice through the balloon. That is what we want to happen.

Letting the cream sit at room temperature does something else. It allows lactic acid bacteria to grow. We think of bacteria as a bad thing, but many of them are quite useful. These bacteria make the cream more acidic, which prevents the growth of harmful bacteria. They also produce chemicals that give the butter a stronger and richer flavor.

When you shake the cream, some of the globules slam into the glass and break open. Soon, the cream is filled with tiny globs of butter. As these tiny bits of butter bump into each other, they stick together. The lumps of butter get larger and larger, as more and more globules are ripped open. Very quickly, you have one large lump of butter and a small amount of liquid buttermilk. I was amazed at how little liquid was left once the butter formed.

You will probably notice that the color of your butter is more pale that the stuff you buy at the store. That is because the manufacturer adds color to it, to make it look more like what people expect butter to look like. I suppose you could color your butter if you wanted to, but I like it just as it is.

A quick trip to the bakery and I had some fresh, hot French bread to give my fresh butter a real test.

From Robert Krampf's Science Education Company

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