Espresso machine
From Wikipedia, the free encyclopedia
- Further information: Espresso
An espresso machine is used to produce the traditional Italian coffee beverage called espresso.
Generally, espresso is produced by forcing 90°C (200°F) water through 7-10 grams of finely ground coffee, which has been compressed with approximately 30 lbf (130 N) of force into a densely packed puck, at a pressure of 900 kPa (9 bars) or greater.
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[edit] Types of espresso machines
Since their invention in 1901, multiple machine designs have been created to produce espresso. They generally share some common elements. The portafilter (or group handle) contains a metal filter-basket and holds the ground coffee. It is locked under the group head's diffusion block.
An ideal double shot of espresso should take 20-25 seconds to arrive, timed from when the machine's pump is first turned on. 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 right into a pre-heated demitasse cup or shot glass, to maintain the ideal temperature of the espresso.
An espresso machine may also have a steam wand which is used to steam and froth milk for beverages such as the cappuccino and latte.
[edit] Steam-driven
A steam-driven unit operates by forcing water through the coffee by using steam or steam pressure. The first espresso machines were steam types, produced when a common boiler was piped to four group heads so that multiple types of coffee could be made at the same time.[1] The design is still used today in low-cost consumer machines, as it does not need to contain moving parts.
[edit] Piston-driven
The piston, or lever, driven machine was developed in 1945 by Achille Gaggia in Italy. The design generically uses lever, pumped by the operator, to pressurize hot water and send it through the coffee grinds. The act of producing a shot of espresso is colloquially termed pulling a shot, because these lever-style espresso machines required pulling a long handle to produce a shot.
There are two types of lever machines; manual piston and spring piston design. With the manual piston, the operator directly pushes the water through the grounds. In the spring piston design, the operator works to tension a spring, which then delivers the pressure for the espresso (usually 8 to 10 bar).
The piston-driven machine is the origin of the crema, which was originally thought to be an undesirable waste product but is now considered characteristic of a properly made shot of espresso.[citation needed]
[edit] Pump-driven
A refinement of the piston machine is the pump-driven machine, which has become the most popular design in commercial espresso bars. Instead of using manual force, a motor-driven pump provides the force necessary for espresso brewing. Commercial or some high-end home machines are often attached directly to the plumbing of the site; lower-end home machines have built-in water reservoirs.
Home (consumer-grade) pump espresso machines typically use a single chamber both for heating water to brewing temperature, and to boil water for steaming milk. Since the optimum temperature for brewing coffee is much less than the temperature for creating steam, the machine requires time to make the transition from one mode to the other. Commercial-grade and "semi-commercial" high end home espresso machines use the boiler chamber only for making steam. Water for brewing most commonly passes through a heat exchanger (taking some heat from the steam, without rising to the same temperature). In a few commercial espresso machines (notably La Marzocco), water for brewing is heated in a separate chamber.
[edit] Variations
[edit] Semi-automatic, automatic, and super automatic
Machines which contain the addition of pumps, sensors, valves, and grinders to automate the brewing process generally are referred to as automatic.
- Semi-automatic machines are automatic in the sense water is delivered by a pump, rather than manual force and remaining brew pressure in the basket is dissipated with a three way valve.
- Automatic machines add a flowmeter inline with the grouphead. When the programmed amount of water has flowed through the flowmeter, the pump is automatically turned off and brew pressure released through a three way solenoid valve.
- Super-automatic machines operate by automatically grinding the coffee, tamping it, and extracting; all an operator needs to do is fill the bean hopper, and if the machine is not connected to a water line, add water to a reservoir. Additionally, models contain an automated milk frothing and dispensing device.
[edit] Air-pressure driven
A handpresso is a small handheld high-pressure espresso machine. It works by pumping air at very high pressure (16 bar) into an intermediate chamber. Hot water is then poured into a small reservoir, which can contain hot water for one cup of espresso coffee (45ml). Ground coffee is inserted on top of the water reservoir and a portafilter is screwed on the top of the water reservoir. The machine is now turned around and the pressure from the intermediate chamber is released into the water reservoir. The high pressure forces the water through the coffee pod and into the cup, which is positioned underneath the device. When the desired amount of espresso coffee is brewed, the pressure is released from the water reservoir and the infusion process stops.
The advantages of the handpresso are that it can be used to make a real high-pressure espresso with the characteristic crema, wherever hot water is available. The Handpresso was invented and designed by Nielsen Innovation in 2006 and the first products were sold in 2007.
[edit] Stovetop
- Main article: Moka pot
While not an espresso producing device, so-called stovetop espresso makers produce a dark coffee with an extraction ratio similar to that of a conventional espresso machine. The bottom chamber contains the water. The middle chamber is a filterbasket and sits within the bottom chamber holding the ground coffee. The top chamber, with a metal filter, screws onto the bottom chamber. When the pot is heated on a stove, the pressure from the steam in the bottom chamber forces the water through a tube into the filter-basket, through the ground coffee, the metal filter, and it then funnels into the top chamber where the coffee is then ready to serve. Stovetop espresso makers produce dark coffee, but they usually lack the necessary pressure which creates a foam emulsion known as crema. However you can make your own sugar crema easily. Use a separate serving pot with desired amount of sugar in it depending on the size of your Moka 2,4,6 or even 8 cup machines are available. One and a half teaspoons of sugar per cup is a good ratio. Simply pour the first teaspoon or so of espresso the machine makes into the separate serving pot with the sugar in it, close the lid back down to let the machine finish brewing. While it brews, whip the sugar with a spoon, with the teaspoon of coffee in the serving pot rapidly until it turns frothy and no longer gritty. Pour the rest of the brewed coffee into serving pot with froth in bottom, stir gently. The crema will float on top and is much tastier that the automatic machines. Serve into cups and enjoy. Commonly found in Italy, Spain and Portugal, stovetop espresso makers are known colloquially as moka pots, after an early trademark. They are also known as a macchinetta, Italian for "little machine". They are also referred to as Spanish coffee makers, or cafeteras in Spanish.
[edit] See also
[edit] References
[edit] External links
- How an espresso machine works
- Italian Espresso National Institute
- International Institute of Coffee Tasters
- Coffee Taster, the free newsletter of the International Institute of Coffee Tasters, featuring articles on the quality of espresso, chemical and sensory analysis, market trends
- Future trend: espresso and cappuccino coffee machine with pre-fabricated air-tight capsules
- Revolutionary coffee making: scam or competitors fight back - you decide
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