Science first, recipe second (if you want the recipe and no science, just skip to the bottom)
Today we will look at cream and its various states. First, and primarily, we know cream as a milk product. It is composed of a high-butterfat content (important in our discussion today) and is skimmed off the top of milk collected from cattle, before the milk is homogenized. We homogenize milk so that the fat molecules do not separate from the water content, that homogenization process is achieved through centrifuges.
Heavy cream is an emulsion, which is to say it is tiny droplets of one liquid floating in another liquid evenly distributed. In this case, globs of fat are suspended perfectly in water making it a fat-in-water emulsion. Throughout the butter making process we will transform the cream into a second kind of emulsion, water-in-fat.
But first, thoughts on that splendid milk fat. Because of its high percentage of fat, cream has the ability to do miraculous things. It can transform in front of our eyes. Primarily we know transformed cream by the name whipped cream. But what happens when we whip cream. Essentially, what we’re doing here is trapping air bubbles in a network of fat droplets. We are pushing the fat closer together and that is what provides structure out of a seemingly structureless ingredient (moving from liquid to semi-solid). The reason we have cream specifically designated as Heavy Whipping Cream is because in order to aerate the liquid we need at least a 30% fat content.
You should be able to achieve whipped cream by shaking the jar for about 3-4 minutes. If whipped cream is, indeed, your end goal then I suggest adding a touch of sugar and some vanilla to the cream before you begin shaking. That way the finished product is already sweetened and ready to top your favorite pie.
But if we keep shaking, do you know what happens? Those fat droplets get closer and closer together, becoming more and more dense. As they get closer together, they press out water and protein. And what do we call dense fat droplets smashed together out of cream? Butter!
Once the cream has been shaken for about 7-10 minutes we can see two distinct forms in the jar: the solid butter mash, and the surrounding liquid. What is the liquid? Why it’s nothing more than buttermilk! Yes, a few weeks ago we discussed imitation buttermilk (regular milk plus vinegar), but this is the real deal. It is the byproduct of butter. Buttermilk is acidic and slightly thick when compared to regular milk. Why so acidic? Because the fat molecules have pressed out most of the milk proteins.
When you reach this point with the cream, you can strain out the butter and then run it under cold water while you knead it. We knead the butter to remove even more water content. I use ice water for the kneading process to ensure that the fat (butter) doesn't melt.
While we need to remove most of the water, we will not get rid of it entirely. Which brings me back to my original talking point on emulsions. We have now achieved the second emulsion, water-in-fat. It is important to note that there is some water trapped in the final butter product, and that water content is part of what makes butter incredible. It helps keep butter spreadable and soft. If we want to remove that water content altogether, we must heat the butter slowly to evaporate the H2O. In doing so, we are beginning the process of making clarified, or refined butter. But this is a lesson to be taught another day.
For now, enjoy your butter, I hope you're shaking!
- 1 pint Jar
- 1/2 pint Heavy Whipping Cream
- Salt, sugar, vanilla, etc (these glaring agents are not necessary and are up to your discretion)
- Fill the pint jar halfway with the cream. It is important to have lots of headspace above the cream. We need that space so that the fat molecules have room to smash into each other and so that once the cream is aerated (i.e. whipped) it has enough space for that growth.
- Shake the jar constantly and with good force for 6-10 minutes. Around 3 minutes you will have whipped cream. You'll know its presence in the jar by the accompanying silence. When you begin, the sloshing cream will make a recognizable sound. Once it is aerated (whipped) It will no longer make sound. From 4 minutes to 6 minutes the shaking will be quite challenging. It will feel like you are shaking a solid object and that nothing is happening. Persevere! Things are happening! Fat is smashing! Out of nowhere you will begin to hear a clump-clump sound. This is terrific. You are close to achieving butter. When you hear feel the butter solid slamming around in milk you are finished.
- Remove the butter solid from the jar and rinse and knead under ice water. You will have roughly half a cup of butter from that half pint of milk.