The process of making espresso can
be seen as an art form, and people who have perfected the technique are
referred to as baristas, masters of several nuances that can affect the
final product. High-end Italian commercial espresso machines, which can
cost $2,000 to $10,000 or more, are too expensive for most consumers.
In Europe, you can find one of these in almost every bar, restaurant and
cafe.
The act of producing a shot of espresso is colloquially termed "pulling" a shot. The term derives from lever-style espresso machines that require pulling a long handle to produce a shot. To pull a single shot of espresso, a metal filter known as a portafilter basket is filled with between 6.5 grams and 10 grams (for a single shot) of properly ground roasted coffee beans. The espresso is then tamped, or compressed with approximately 30 lbf (130 N) of force into a densely packed puck of espresso. The portafilter (or group handle) is finally inserted up into the grouphead on the espresso machine and locked into place. When the machine is turned on, a pressurized stream of hot water at 90 +/-5 °C (200 +/-5 °F) and approximately 900 kPa (130 PSI) is forced through the grouphead and down through the ground coffee in the portafilter. Water cooler than the ideal temperature zone causes sourness; hotter than the ideal zone causes bitterness. High-quality espresso machines are designed to carefully control the temperature of the brewhead to within a few degrees of the ideal.
Some individuals (and almost all accomplished baristas) prefer to pour right into a pre-warmed demitasse, a small cup used for espresso. Espresso is a fleeting beverage, and the flavour will begin to degrade immediately. It is also a fragile beverage, which is damaged through transferring from one container to another.
Time is a critical element in pulling a good shot. The ideal shot will be produced in 25 +/-5 seconds of extraction with a molasses-like flow. Varying the fineness of the grind, the amount of pressure used to tamp the grinds, and the pressure of the espresso machine itself can be used to bring the extraction time into this ideal zone.
Espresso was invented in Italy, where it is said that four Ms are key to a good espresso: miscela (blend), macinazione (grind), macchina (machine), and mano (hand).
A recent brewing trend came with the invention of the naked portafilter, that is, a grouphead without the bottom half, exposing the portafilter during pulling. Some claim that by looking for certain characteristics, such as color, evenness, duration of how the liquid flows out of portafilter, one can get a sense of how the coffee will ultimately taste. By studying the pull, the brewer can accordingly adjust the granularity of the grind, amount of coffee to add, the amount of pressure to use when tamping, water temperature and pressure to produce consistantly pleasant tasting coffee cup after cup.
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| An espresso machine is used to produce the
traditionally Italian coffee beverage called espresso. An espresso machine is used to produce the traditionally Italian coffee beverage called espresso. An espresso machine forces water at 90 °C (195 °F) and 9 bar of pressure through a puck of finely ground coffee. This process produces a rich, almost syrupy beverage by extracting and emulsifying the oils in the ground coffee. An ideal double shot of espresso should take 20-25 seconds to arrive, timed from when the machine's pump is first turned on. This time can be tuned by using finer or coarser ground coffee, and by altering the tamping pressure. An espresso machine also has a steam wand which is used to steam and froth milk for milk based espresso beverages such as the cappuccino and latte... More >>
Pump-Driven Espresso Machine
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