Butter is produced by churning cream, a process which damages the membranes of butterfat found in cream resulting in the production of small butter grains. These butter grains float in the water-based portion of the cream called buttermilk. The buttermilk is then drained and if required more buttermilk can be removed by rinsing the grains with water. Finally the grains are pressed and kneaded together. Slight variations in the production method allow the creation of butters with different consistencies.
There are several types of butter but sweet cream butter, which is made from pasteurised cream, is the most common type used in the UK. There are also several spreadable butters which remain softer at colder temperatures and are therefore easier to use directly from the fridge. Whipped butter is also designed to be more spreadable, and is created by a process of aeration involving nitrogen gas.
All categories of butter are sold as salted or unsalted. Salt is added as flavouring.