cup of coffee

Coffee is a brewed beverage prepared from the roasted or baked seeds of several species of an evergreen shrub of the genus Coffea. The two most common sources of coffee beans are the highly regarded Coffea arabica, and the "robusta" form of the hardier Coffea canephora. The latter is resistant to the coffee leaf rust (Hemileia vastatrix), but has a more bitter taste. Coffee plants are cultivated in more than more than 70 countries, primarily in equatorial Latin America, Southeast Asia, and Africa. Once ripe, coffee "berries" are picked, processed and dried to yield the seeds inside. The seeds are then roasted to varying degrees, depending on the desired flavor, before being ground and brewed to create coffee. Coffee percolators 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 grounds are retained in the filter.[93] In a percolator, boiling water is 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,[93] or by a thermostat that turns off the heater when the entire pot reaches a certain temperature. Coffee may be brewed by steeping in a device such as a French press (also known as a cafetière, coffee press or coffee plunger).[94] Ground coffee and hot water are combined in a cylindrical vessel and left to brew for a few minutes. A circular filter which fits tightly in the cylinder fixed to a plunger is then pushed down from the top to force the grounds to the bottom. The filter retains the grounds at the bottom as the coffee is poured from the container. Because the coffee grounds are in direct contact with the water, all the coffee oils remain in the liquid, making it a stronger beverage. This method of brewing leaves more sediment than in coffee made by an automatic coffee machine.[94] Supporters of the French press method point out that the sediment issue can be minimized by using the right type of grinder: they claim that a rotary blade grinder cuts the coffee bean into a wide range of sizes, including a fine coffee dust that remains as sludge at the bottom of the cup, while a burr grinder uniformly grinds the beans into consistently-sized grinds, allowing the coffee to settle uniformly and be trapped by the press.[95] 95% of the caffeine is released from the coffee seeds within the first minute of brewing. The espresso method forces hot pressurized and vaporized water through ground coffee. As a result of brewing under high pressure (ideally between 9–10 atm), 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.[96] A well-prepared espresso has a reddish-brown foam called crema that floats on the surface.[91] Other pressurized water methods include the moka pot and vacuum coffee maker. Cold brew coffee is made by steeping coarsely ground seeds in cold water for several hours, then filtering them.[97] This results in a brew lower in acidity than most hot-brewing methods.