Butter is manufactured from dairy cream using a churning process. The cream is produced by passing milk through a separator, which divides the incoming milk into skim milk (0.1% milkfat) and cream (35-40% milkfat).
Cream is churned until small butter grains form in buttermilk. The buttermilk is drained and the churning process continues until the grains are kneaded together. Salt is typically added and this adds flavour to the butter and also enhances its shelf-life. It requires about twenty litres of whole milk to produce one kilogram of butter.
The churning process results in a water-in-oil emulsion. The final product is around 80% milkfat, and 16% water in the form of very tiny droplets. The smooth texture of butter is closely linked to the working (kneading) process.
In addition to milkfat and water, normal butter contains salt (1.5-2.0%), trace amounts of protein, calcium, phosphorous, and various fat-soluble vitamins (A, D, and E).
Butter should have a uniform colour, and a smooth consistency so that it is easy to spread and readily melts on the tongue.
While there are various kinds of butter, the most common is sweet cream butter, which is made from pasteurised cream. Recent developments include reduced-fat butter, lite butter, and spreadable dairy blends which are softer at refrigeration temperatures.
Types of butter
Cultured butter: the cream is cultured using bacteria which sour the cream, producing butter with an enhanced flavor.
Dairy blends and spreads: are a mixture of butter and vegetable oils (usually canola or olive).
Whipped butter: has had air or other gases whipped into it, resulting in a product with greater volume (reduced density) and better spreadability at refrigeration temperatures.