butter

Solid, edible yellowish fat made from whole milk. Making butter by hand, which is done by skimming off the cream and churning it, was traditionally a convenient means of preserving milk.

The transfer of butter making from a farm-based to a factory-based process began in the last quarter of the 19th century, with the introduction of centrifugal separators for the instant separation of cream from milk. It could then be conveyed into large steam-powered churns. Today, most butter is made on a continuous system devised in Germany during World War II. Inside a single machine, the cream is churned, the buttermilk drawn off, and the butter washed, salted, and worked, to achieve an even consistency. Colour and flavouring may be added. A continuous stream of finished butter is extruded from the machine ready for wrapping.

Salted butter has a longer shelf-life than sweet butter, salt being added as a preservative.