butter

Butter is a dairy product made from the fat and protein components of milk or cream. Cream is a dairy product composed of the higher-fat layer skimmed from the top of milk before homogenization [均匀化]. Butter is a semi-solid emulsion at room temperature, consisting of approximately 80% butterfat. It is used at room temperature as a spread, melted as a condiment, and used as an ingredient in baking, sauce making, pan frying, and other cooking procedures.

Most frequently made from cow's milk, butter can also be manufactured from the milk of other mammals, including sheep, goats, buffalo, and yaks. It is made by churning milk or cream to separate the fat globules from the buttermilk. Salt and food colorings are sometimes added to butter. Rendering butter, removing the water and milk solids, produces clarified butter or ghee, which is almost entirely butterfat.

Butter is a water-in-oil emulsion resulting from an inversion of the cream, where the milk proteins are the emulsifiers. Butter remains a firm solid when refrigerated, but softens to a spreadable consistency at room temperature, and melts to a thin liquid consistency at 32 to 35 °C (90 to 95 °F). The density of butter is 911 grams per litre (0.950 lb per US pint). It generally has a pale yellow color, but varies from deep yellow to nearly white. Its natural, unmodified color is dependent on the source animal's feed and genetics, but the commercial manufacturing process commonly manipulates the color with food colorings like annatto or carotene.

inversion: cream是飘在水上的油，黄油是油包水。1克butter 7.57大卡。越野滑雪每十分钟消耗260卡路里的说法是错误的

The word butter derives (via Germanic languages) from the Latin butyrum, which is the latinisation of the Greek βούτυρον (bouturon). This may be a compound of βοῦς (bous), "ox, cow" + τυρός (turos), "cheese", that is "cow-cheese". The latinized form is found in the name butyric acid, a compound found in rancid butter and dairy products such as Parmesan cheese.

In general use, the term "butter" refers to the spread dairy product when unqualified by other descriptors. The word commonly is used to describe puréed vegetable or seed and nut products such as peanut butter and almond butter. It is often applied to spread fruit products such as apple butter. Fats such as cocoa butter and shea butter that remain solid at room temperature are also known as "butters". Non-dairy items that have a dairy-butter consistency may use "butter" to call that consistency to mind, including food items such as maple butter and witch's butter and nonfood items such as baby bottom butter, hyena butter, and rock butter.

Unhomogenized milk and cream contain butterfat in microscopic globules. These globules are surrounded by membranes made of phospholipids (fatty acid emulsifiers) and proteins, which prevent the fat in milk from pooling together into a single mass. Butter is produced by agitating cream, which damages these membranes and allows the milk fats to conjoin, separating from the other parts of the cream. Variations in the production method will create butters with different consistencies, mostly due to the butterfat composition in the finished product. Butter contains fat in three separate forms: free butterfat, butterfat crystals, and undamaged fat globules. In the finished product, different proportions of these forms result in different consistencies within the butter; butters with many crystals are harder than butters dominated by free fats.

Churning produces small butter grains floating in the water-based portion of the cream. This watery liquid is called buttermilk—although the buttermilk most common today is instead a directly fermented skimmed milk. The buttermilk is drained off; sometimes more buttermilk is removed by rinsing the grains with water. Then the grains are "worked": pressed and kneaded together. When prepared manually, this is done using wooden boards called scotch hands. This consolidates the butter into a solid mass and breaks up embedded pockets of buttermilk or water into tiny droplets.

Commercial butter is about 80% butterfat and 15% water; traditionally made butter may have as little as 65% fat and 30% water. Butterfat is a mixture of triglyceride, a triester derived from glycerol and three of any of several fatty acid groups. Butter becomes rancid when these chains break down into smaller components, like butyric acid and diacetyl. The density of butter is 0.911 g/cm3 (0.527 oz/in3), about the same as ice.

In some countries, butter is given a grade before commercial distribution.

In the United States, butter has traditionally been made into small, rectangular blocks by means of a pair of wooden butter paddles. It is usually produced in 4-ounce (110 g) sticks that are individually wrapped in waxed or foiled paper, and sold as a 1 pound (0.45 kg) package of 4 sticks. Outside of the United States, the shape of butter packages is approximately the same, but the butter is measured for sale and cooking by mass (rather than by volume or unit/stick), and is sold in 250 g (8.8 oz) and 500 g (18 oz) packages.

标签：butter,Butter,fat,water,milk,cream
来源： https://www.cnblogs.com/funwithwords/p/15962827.html