Brewing Espresso

Preparation of espresso requires an espresso machine. The act of producing a shot of espresso is termed "pulling" a shot. The term derives from lever espresso machines, which require pulling down a handle attached to a spring-loaded piston, forcing hot water through the coffee at the requisite pressure.

To pull a shot of espresso, a metal filter-basket is filled with 7 to 10 grams of ground coffee for a single shot or 12 to 18 grams for a double shot. The espresso is then tamped, using about 40 pounds (180 N) of force, evenly and rotationally applied, into a firm puck of coffee. The portafilter (or group handle) holds the filter-basket and is locked under the grouphead's diffusion block. When the brew process begins, pressurized water at 90±5 °C (194±9 °F) and approximately 90 kPa (13 psi; 0.9 bar) is forced into the grouphead and through the ground coffee in the portafilter. Water, cooler than the ideal zone, causes sourness; hotter than the ideal zone causes bitterness. High-quality espresso machines control the temperature of the brew water within a few degrees of the ideal. The serving temperature of espresso is significantly lower, typically around 60 to 70 °C (140 to 160 °F), owing to the small serving size and the cooling effects of the cup and of the pouring process.

This process produces a rich, almost syrupy beverage by extracting and emulsifying the oils in the ground coffee. An ideal shot of espresso should take between 20 and 30 seconds to arrive on a professional-grade machine, timed from when the coffee begins to flow from the machine(unless the machine has a "preinfusion" stage, which may add about 7 seconds to the process). Varying the fineness of the grind, the amount of pressure used to tamp the grinds, or the pump pressure itself can be used to bring the extraction time into this ideal zone. Most prefer to pull espresso shots directly into a pre-heated demitasse or shot glass, to maintain the ideal temperature of the espresso and preserve all of its crema. Apart from the espresso made manually by a barista, espresso is also made by automatic machines in which the brewing process takes place with an espresso-brewer.

Freshly brewed espresso must be served or mixed into other coffee beverages immediately, or it will begin to degrade due to cooling and oxidation. Temperature and time of consumption are important variables that must be observed to enjoy an ideal espresso; it should be consumed within 2 minutes from when it is served.

Espresso roast
A common misconception about espresso is that it is a specific bean or roast level. Any bean or roasting level can be used to produce authentic espresso. While some major North American chains push dark roasts as their espresso roasts, some of the winning blends used in the World Barista Championship have been what is classified as a medium or "City" or "Full City" roast, with little or no visible surface oil on the beans.

The popularity of different levels of roast in espresso varies greatly. Espresso is typically made from a blend of beans roasted anywhere from very light to very dark. In Southern Italy, a darker roast is preferred but in Northern Italy, a more medium roast is the most popular type. Companies such as Starbucks and Peets have popularized darker roasts in North America and around the world, but the current trend in espresso coffee is matching the roast level to the bean type; this means that the most popular roast style is moving away from being associated with roast color, and more associated with what will produce the best flavor extraction in the cup for each region and type of bean.



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