Coffee
Brewing

Coffee beans must be ground and brewed to create a beverage. The criteria for choosing a method include flavor and economy. Almost all methods of preparing coffee require that the beans be ground and then mixed with hot water long enough to allow the flavor to emerge but not so long as to draw out bitter compounds. The liquid can be consumed after the spent grounds are removed. Brewing considerations include the fineness of the grind, how the water is used to extract the flavor, the ratio of coffee grounds to water (the brew ratio), additional flavorings such as sugar, milk, and spices, and the technique to be used to separate spent grounds. Optimal coffee extraction occurs between 91 and 96 °C (196 and 205 °F). Ideal holding temperatures range from 85 to 88 °C (185 to 190 °F) to as high as 93 °C (199 °F) and the ideal serving temperature is 68 to 79 °C (154 to 174 °F).

Coffee beans may be ground with a burr grinder, which uses revolving elements to shear the seed; a blade grinder cuts the seeds with blades moving at high speed; and a mortar and pestle crush the seeds. For most brewing methods a burr grinder is deemed superior because the grind is more even and the grind size can be adjusted. The type of grind is often named after the brewing method for which it is generally used, Turkish grind being the finest, while coffee percolator or French press are the coarsest. The most common grinds are between these extremes: a medium grind is used in most home coffee-brewing machines.

Coffee may be brewed by several methods. It may be boiled, steeped, or pressurized. Brewing coffee by boiling was the earliest method, and Turkish coffee is an example of this method. It is prepared by grinding or pounding the seeds to a fine powder, then adding it to water and bringing it to a boil for no more than an instant in a pot called a cezve or, in Greek, a μπρίκι: bríki (from Turkish ibrik). This produces a strong coffee with a layer of foam on the surface and sediment (which is not meant for drinking) settling at the bottom of the cup.

Drip brewers and automatic coffeemakers brew coffee using gravity. In an automatic coffeemaker, hot water drips onto coffee grounds that are held in a paper, plastic, or perforated metal coffee filter, allowing the water to seep through the ground coffee while extracting its oils and essences. The liquid drips through the coffee and the filter into a carafe or pot, and the spent coffee grounds are retained in the filter.

In a coffee percolator, water is pulled under a pipe by gravity, which is then forced into a chamber above a filter by steam pressure created by boiling. The water then seeps through the grounds, and the process is repeated until terminated by removing from the heat, by an internal timer, or by a thermostat that turns off the heater when the entire pot reaches a certain temperature.

The espresso method forces hot pressurized water through finely-ground coffee. As a result of brewing under high pressure (typically 9 bar), the espresso beverage is more concentrated (as much as 10 to 15 times the quantity of coffee to water as gravity-brewing methods can produce) and has a more complex physical and chemical constitution. A well-prepared espresso has a reddish-brown foam called crema that floats on the surface. Other pressurized water methods include the moka pot and vacuum coffee maker. The AeroPress also works similarly, moving a column of water through a bed of coffee.

Cold brew coffee is made by steeping coarsely ground beans in cold water for several hours, then filtering them. This results in a brew lower in acidity than most hot-brewing methods.
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