Butter

Butter is a dairy product created by churning cream, which separates its fat and protein components. At room temperature, it forms a semi-solid emulsion containing roughly 81% butterfat. People use it as a spread at room temperature, melt it as a condiment, and employ it as a cooking fat for baking, sauces, pan frying, and other methods. While most butter comes from cow's milk, it can also be made from the milk of sheep, goats, buffalo, and yaks.

The word butter traces back through Germanic languages to the Latin *butyrum*, itself a Latinization of the Greek *βούτυρον* (*bouturon*). This Greek term may combine *βοῦς* (*bous*, "ox" or "cow") with *τυρός* (*turos*, "cheese"), meaning "cow-cheese." The word *turos* appears in Mycenaean Greek. The Latinized form survives in the name butyric acid, a compound found in rancid butter and other dairy products.

Unhomogenized milk and cream hold butterfat in microscopic globules, each surrounded by membranes of phospholipids and proteins that prevent the fat from clumping. Agitating cream damages these membranes, letting the milk fats join together and separate from the rest of the cream. Different production methods yield butters with varying consistencies, mainly due to the butterfat composition. Butter contains fat in three forms: free butterfat, butterfat crystals, and intact fat globules. The proportions of these forms determine the butter's hardness—more crystals make it firmer, while more free fats make it softer.

Churning produces small butter grains floating in the watery portion of the cream, called buttermilk (though buttermilk can also be directly fermented skimmed milk). The buttermilk is drained off, and sometimes the grains are rinsed with water to remove more buttermilk. The grains are then "worked"—pressed and kneaded together, traditionally using wooden boards called scotch hands—to consolidate the butter into a solid mass and break up any remaining pockets of buttermilk or water into tiny droplets.

Commercial butter is about 80% butterfat and 15% water, while traditionally-made butter may have as little as 65% fat and 30% water. Butterfat is a mixture of triglycerides (triesters of glycerol and three fatty acids), which make up about 97% of the fat in milk. Salt has been added to butter since ancient times to help preserve it, especially during transport; while refrigeration has reduced salt's preservation role, it is still added for taste. Modern butter may also include food coloring. In the U.S., annatto is sometimes added without being declared on the label, as U.S. regulations allow butter to contain an undisclosed flavorless natural coloring agent (unlike other foods, which must list such additives). The preservative lactic acid can replace salt (and enhance flavor), and extra diacetyl may be added for a buttery taste; in the U.S., both can be listed simply as "natural flavors." When used together in the NIZO manufacturing method, these two flavorings mimic the taste of cultured butter without full fermentation.

Rendering butter—removing water and milk solids—produces clarified butter (including ghee), which is almost entirely butterfat. Butter is a gel. It stays firm when refrigerated, softens to a spreadable consistency at room temperature, and melts into a thin liquid at 32 to 35 °C (90 to 95 °F). Its density is 911 g/L (15¼ oz/US pt). Butter generally has a pale yellow color but can range from deep yellow to nearly white. Its natural color depends on the source animal's feed and genetics, though commercial processes sometimes alter it with colorings like annatto or carotene.

Before modern factory production, cream was often collected from several milkings and was several days old, somewhat fermented by the time it was churned. Butter made this way—from fermented cream—is called cultured butter. During fermentation, bacteria convert milk sugars into lactic acid, naturally souring the cream and producing additional aroma compounds like diacetyl, giving a fuller, more "buttery" flavor. Butter made from fresh cream is called sweet cream butter. Sweet cream butter became common in the 19th century, when refrigeration and the mechanical milk separator made it faster and cheaper to produce at scale (sweet cream butter can be made in 6 hours, while cultured butter can take up to 72 hours). Cultured butter is preferred throughout continental Europe, while sweet cream butter dominates in the United States and the United Kingdom. Chef Jansen Chan, director of pastry operations at the International Culinary Center in Manhattan, notes that dairy in France and most of Europe is generally higher quality than in the U.S., attributing this to the combination of butter culturing, a minimum 82% butterfat (versus 80% in the U.S.), and the use of grass-fed milk, which accounts for the richer taste and flakiness of French pastry and food. Cultured butter is sometimes labeled "Europe."

In 2023, world production of cow's milk butter reached six million tonnes, with the United States leading at 16% of the total.