Key Concepts
Chemistry, fat, heat

Introduction

Have you ever wondered how butter is made?  Butter is used in many tasty applications – hot pancakes with butter running down the sides, freshly baked biscuits and pastries with butter, and hot flaky potatoes with melted butter, to name just a few. Yum!  While making butter can be hard work, it can also be easily made at home.  In this activity you’ll not only get to find out how butter’s made, but also how temperature affects the butter-making process.  And then you may enjoy the fruits (or rather, butter!) of your labors!

This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Background

Butter is an ancient prepared food, having been made by people at least 4000 years ago.  Some of the earliest known recipes call for the use of a vessel made from animal skin.  The skin would be sewed together tightly, leaving a small opening through which to add fatty milk or cream.  The vessel would then be suspended, such as from wooden poles, and swung until butter formed.  For the last century, butter has been progressively produced in factories and is now used in many products, including cake batters and pastries, usually to produce a flaky or creamy texture and a delicious, rich flavor.

One traditional butter-making process begins with making cream.  When milk sits out, tiny fat molecules float to the top of the milk, forming a layer of cream that can be skimmed and collected.  To make butter from the cream, the cream is agitated (stirred up) so that the fat molecules get shaken out of position and clump together.  Eventually, after enough agitation, the fat molecules clump so much that butter forms.  When butter forms, the fat molecules have clearly separated from the liquid in the cream, and this liquid can be removed and made into buttermilk.

Materials

  • Measuring cup
  • 1 cup of heavy whipping cream 
  • Cup or glass
  • Clean 1-quart glass jar with lid and a tight seal. A canning jar with a lid, seal, and ring works best.  A different sized jar could be used but the amount of heavy whipping cream should be adjusted accordingly.
  • Helper (optional)
  • Stopwatch or clock
  • Bowl
  • Cold water
  • Small plastic bags

Preparation

  1. Pour ½ cup of heavy whipping cream into a cup or glass.  Let it sit out at room temperature for 5 hours.

Procedure

  1. After the ½ cup of heavy whipping cream has sat out for 5 hours, pour it into a clean 1-quart glass jar.  Tightly put the lid on the jar.
  2. For the next step, you may want to get a helper ready to trade off on shaking the jar.  It will take several minutes of shaking to make butter from the cream!
  3. Start shaking the jar and at the same time start the stopwatch or note what time it is.  Shake the jar until butter forms.  This could take between 5 to 20 minutes.  How does the heavy whipping cream change as you shake the jar?  When the cream thickens (within a couple of minutes of when you start shaking), keep shaking the jar!  Once you have shaken the jar enough the liquid will suddenly separate from the butter.  The butter will be a pale yellow lump, while the liquid will be milky.  You’ll probably hear the lump hitting the sides of the jar as you shake it.  Stop shaking the jar and stop the stopwatch when the butter and liquid separate.  
  4. How long did it take the butter to form when using room-temperature cream? How does the butter and liquid in the jar look?
  5. Carefully pour the liquid out of the jar.  You can store the liquid and later turn it into buttermilk for use in other recipes.
  6. Remove the lump of butter from the jar and place it in a bowl of cold water.  Gently knead the butter to remove any extra liquid.  Use your fingers to drain the liquid from the bowl.  Rinse the butter two more times in this way.  (If the liquid is not removed, the butter will go rancid faster.)
  7. Transfer the butter into a small plastic bag and store it.
  8. Clean the jar, its lid, and the bowl.
  9. Repeat the entire butter-making process as you just did but this time use ½ cup of cold heavy whipping cream straight from the refrigerator (instead of room-temperature heavy whipping cream).  Try to shake the jar similarly.  How long did it take the butter to form when using cold cream?  How does the butter and liquid in the jar look?
  10. Overall, how long did it take butter to form using the warmer heavy whipping cream compared to the colder cream? Does it look like the temperature affects how quickly the cream turns into butter?

Extra: Repeat this activity a few more times.  Do you get similar results each time you use cold heavy whipping cream or room-temperature cream, or is there variation in your results? 

Extra: Weigh the amount of heavy whipping cream that you start with and then weigh the amount of butter that you end with.  What percent of cream is turned into butter?

Extra: In this activity you investigated how temperature affects turning heavy whipping cream into butter but you did not quantify the temperatures you used.  You could repeat this activity but this time use a thermometer to measure the temperature of the cream when you put it into the glass jar.  You could even try some different temperatures of cream and see how that affects the process.  How do different temperatures of cream affect the butter-making process?

Observations and Results

Did it take a much longer amount of time to make butter using the cold heavy whipping cream compared to using the room-temperature heavy whipping cream?  Aside from this difference, did both butters seem similar?

As you shook each jar, you should have seen and heard the cream initially slosh around, and then gradually thickened.  Eventually, after several seconds (but less than two minutes), it should have become so thick that it didn’t move much as you shook the jar.  At this point the cream had likely turned into whipped cream.  After you shook the jar for about 5 to 20 minutes total, the cream should have abruptly turned into butter.  This likely happened much quicker for the room-temperature cream than for the cold cream.  (For example, the room-temperature cream may have become butter after 5 to 6 minutes, whereas the cold cream took 13 to 15 minutes of shaking.)  As the cream is shaken, the fat molecules get out of position and clump together, eventually clumping so much that butter forms.  At this point the fat molecules have clearly separated from the liquid in the cream.  When molecules are heated, they move faster because they have more energy.  Consequently, the molecules in the room-temperature cream moved faster than the ones in the cold cream, allowing the room-temperature fat molecules to clump together faster and form butter faster.

Cleanup

  1. You may enjoy some delicious, homemade butter.  Be sure to store it properly and consume it before it goes rancid.

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Credits

Teisha Rowland, PhD, Science Buddies

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Key Concepts
Chemistry, fat, heat
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