Churning is the act of producing butter by stirring up cream or whole milk, typically with a butter churn. From the Middle Ages until the Industrial Revolution in Europe, a churn was usually as simple as a hand-moved barrel with a plunger inside. These were replaced mostly by mechanical churns.
Butter is the milk fat. Typically rendered with sweet milk. Salt is commonly applied to it in the USA, Britain, the Netherlands, and the Scandinavian countries. In the rest of Europe, unsalted (sweet) butter is most commonly used. It may also be made of acidulated or bacteriologically soured cream, however.
Much through the 19th-century butter was often produced from milk that had been permitted to rise and sour. The cream was then skimmed from the milk surface and poured into a wooden bowl.
The method can be summed up in three steps:
- The churning agitates the cream violently until the delicate membranes covering the milk fat are ruptured. When separated, the fat droplets will shape clumps of fat and bind together.
- When the churning proceeds, larger clusters of fat accumulate before they start creating a network with the air bubbles produced by the churning; this collects the liquid and creates a foam. If the thickness of the fat clumps decreases, the air cells are therefore less sealed. So the bubbles are popping, running together and the foam starts leaking. Buttermilk is the word for this leakage.
- The cream splits up into butter and buttermilk. The buttermilk is drained off, and the remaining butter is kneaded to shape a network of fat crystals which becomes a water-in-fat emulsion continuous process or dispersion medium. Using the butter provides the perfect smoothness too.