Make Butter Two Ways
In this simple science experiment, kids make butter while exploring liquids, solids and the properties of milk.
Simple explanation: churning (or shaking) causes cream (a liquid) to separate into butter (a solid) and buttermilk (a liquid).
Detailed explanation: Cream is mixture of solid butterfat suspended in liquid buttermilk. When shaken, air is trapped in the cream and bubbles form; this creates whipped cream. If you keep shaking, the tiny bubbles eventually begin to pop, and the fat solids begin to stick together in clumps and separate from the liquid buttermilk. This process is called “churning” and has been around for thousands of years.
In the old days, a cow would be milked, then the milk would be strained, poured into a can and stored in cool water (for example, in a well or river). After several hours, the cream would rise to the top. The cream would be skimmed off (leaving behind “skim milk”), then allowed to become warm and slightly sour. It would then be churned into butter. The butter was washed, and sometimes combined with salt to preserve its freshness. The leftover buttermilk was used for drinking or baking. The leftover skim milk was fed to the livestock or made into cottage cheese.
What other products are also made from milk?
Cream is an example of a "colloid." Colloids are liquids that contain tiny solids, drops of other liquids, or gas bubbles that are so evenly spread out and so well mixed-in that they don't settle to the bottom, float to the top or otherwise separate out unless forced to. Other examples are shaving cream and mousse.
Be careful to supervise little ones if using glass jars.
- Heavy cream, slightly warmed - 1/4+ cup per student
- Clean glass jar with lid - 1 of this item per student
- Marble (optional) - 1 of this item per student
- Spatula or wooden spoon - 1 of this item per class
- Bowl - 1 of this item per class
- Blender (optional) - 1 of this item per class
Fill clean glass jar about 3/4 full with heavy cream. You will get butter faster if the cream is slightly warmed (not straight from the fridge) and if you add a marble to the jar to help churn the cream.
You will need to shake the jar about 10 minutes, depending on how hard and how consistently you are shaking it. (With little ones, note that this could take up to 20 minutes unless an adult is helping to shake.)
Whipped cream will form very quickly; eventually you will notice that the sloshing in the jar stops completely and the marble all but stops moving. This is the point when you will be tempted to stop shaking. You could, because the liquid cream will now be a tasty solid that looks and tastes a lot like whipped butter. But if you want to get to the point where the butter fat solids actually separate from the butter milk, you've got to keep on shaking! This separation will happen very quickly -- you will notice a foamy thin liquid forming around solid yellowish chunks. The chunks are the butter. the liquid is buttermilk.
Strain the buttermilk off if you want to use it for cooking, then place the butter solids in a bowl and begin pressing them with a spatula or wooden spoon. Keep pressing and draining the excess buttermilk until no more liquid comes out. Now add salt to taste (salt can be used as a preservative, but you don't need it) and form the butter into a mound. Spread some onto a piece of bread and enjoy!
If you are doing this with a class, especially with young kids, it is best to let the students work in teams so one student isn't shaking the jar the entire time.
If you have trouble getting the butter solids to separate out, it could be because:
- The cream you used didn't have enough fat. Heavy cream works the best.
- The cream was too cold. Warmer cream will separate out faster.
- You didn't shake hard enough or long enough. Adding a marble definitely speeds things up!
If you want to demonstrate how butter can be made more quickly, or differently, you do this activity in a blender in just a few minutes.
This activity is a great companion to lessons on barnyard animals, liquids and solids, phase changes, and the wide range of milk products (yogurt, milk, cheese, whipped cream, ice cream, etc.).