Women on the western frontier had many responsibilities. They managed the needs of the household and shared the hard labor of farming and settling new land. As a pioneer child, Emmy would be hard at work right beside her mother. One chore she would have had was churning milk from their milk cow into butter.
Milk is a colloid: a substance in which small, insoluble particles are suspended in another substance. In the case of milk, those particles are fat globules distributed in a water-based solution.
The cream is the fat rich portion of milk. When fresh straight out of the cow (or goat) milk is left the fatty cream will rise to the top. Until the first hand-cranked milk-cream separator in the late 19th century, procuring fresh cream was a lengthy process waiting for the cream to naturally separate so it could be skimmed off.
When you whip cream a couple of things happen because you are actually changing the physical structure and chemical properties of the lipids within the cream.
Milk fat is a complex mixture of lipids, but the most prevalent one is triglyceride, made by combining three fatty acids and glycerol.
Air is forced into the cream forming bubbles of gas that pop as quickly as they form. The surface tension of cream isn't strong enough to support them. But after a few minutes of whipping the fat globules in the cream begin to destabilize as their protective phospholipid membranes break down.
The water-fearing triglycerides begin sticking together. Some triglyceride however while avoiding water will align with neutral pockets of air. When this happens, a somewhat solid structure of whipped cream is created.
Whipped cream is a Foam; a suspension of gas bubbles in another substance.
Now-a-days we have ready-to-whip, homogenized heavy cream. So how do we turn the Foam cream into solid butter? Whip it, whip it good! How hard and how long you whip have a big effect on your end product.
When you make butter the whipped cream will become thicker and thicker as more fatty triglycerides stick together. Eventually through whipping (or shaking in this case) those triglycerides that aligned with the air will find a fat to bond to and the air will leave the system.
Once the air is gone the network collapses. The water that was held in by the air separates from the solid mass of butterfat. The solid portion is butter ready to be drained and washed.
Helpful Hints from an Old Timer: Keeping everything cold when making whipped cream or butter will help keep the fat in the solid phase.
What you will need to make butter: A thick tempered glass jar with a lid, heavy cream (35% whipping cream) 2-3 glass marbles.
Directions: Fill your jar half full with cream and add the marbles. Put the lid on tightly and begin shaking! The liquid will thicken almost right away and the sound of liquid sloshing around in the jar will dissipate. Keep shaking! About halfway through whipped cream will form.
After a few more minutes, you will hear liquid sloshing around in the jar again. It is the buttermilk starting to separate from the butter. Almost done! Shake it for another minute or so, until the butter is a solid mass.
Scoop it out, letting the watery milk drain off, and place your solid butter in a bowl of clean ice water.
Fold it and press it around the bowl a few times, dumping and replacing the water until it rinses clear.
Dispose of the last bit of rinse water and continue to knead the butter a little while longer, expelling excess liquid. Water promotes microbial growth, and failure to remove the watery skim milk can result in it souring, which would spoil all of your butter.
Pack it tightly together and wrap it in plastic wrap: refrigerate or freeze.