Butter is a dairy product made by churning fresh or fermented cream or milk. It is generally used as a spread and a condiment, as well as in cooking, such as baking, sauce making, and pan frying. Butter consists of butterfat, milk proteins and water. Most frequently made from cows' milk, butter can also be manufactured from the milk of other mammals, including sheep, goats, buffalo, and yaks. Salt, flavorings and preservatives are sometimes added to butter. Rendering butter produces clarified butter or ghee, which is almost entirely butterfat. Butter is a water-in-oil emulsion resulting from an inversion of the cream, an oil-in-water emulsion; the milk proteins are the emulsifiers. Butter remains a solid when refrigerated, but softens to a spreadable consistency at room temperature, and melts to a thin liquid consistency at 32Ц35 ∞C (90Ц95 ∞F). The density of butter is 911 g/L (56.9 lb/ft3). It generally has a pale yellow color, but varies from deep yellow to nearly white. Its unmodified color is dependent on the animals' feed and is commonly manipulated with food colorings in the commercial manufacturing process, most commonly annatto or carotene. Dairy products are generally defined as food produced from the milk of mammals (the Food Standards Agency of the United Kingdom defines dairy as "foodstuffs made from mammalian milk"). They are usually high energy-yielding food products. A production plant for the processing of milk is called a dairy or a dairy factory. Apart from breastfed infants, the human consumption of dairy products is sourced primarily from the milk of cows, yet goats, sheep, yaks, camels, and other mammals are

other sources of dairy products consumed by humans. Dairy products are commonly found in European, Middle Eastern and Indian cuisine, whereas aside from Mongolian cuisine they are little known in traditional East Asian cuisine. Churning is the process of shaking up cream (or whole milk) to make butter, and various forms of butter churn have been used for the purpose. In Europe from the Middle Ages until the Industrial Revolution, this was generally as simple as a barrel with a plunger in it, which was moved by hand. Afterward, mechanical means of churning were usually substituted. Butter is essentially the fat of milk. It is usually made from sweet cream. In the USA, Ireland and the UK, salt is usually added to it. Unsalted (sweet) butters are most commonly used in the rest of Europe. However, it can also be made from acidulated or bacteriologically soured cream. Well into the 19th century butter was still made from cream that had been allowed to stand and sour naturally. The cream was then skimmed from the top of the milk and poured into a wooden tub. Buttermaking was done by hand in butter churns. The natural souring process is, however, a very sensitive one and infection by foreign microorganisms often spoiled the result. Today's commercial buttermaking is a product of the knowledge and experience gained over the years in such matters as hygiene, bacterial acidifying and heat treatment, as well as the rapid technical development that has led to the advanced machinery now used. The commercial cream separator was introduced at the end of the 19th century, the continuous churn had been commercialized by the middle of the 20th century.