Espresso machine
An espresso machine is generally a device for quickly brewing coffee ( espresso ) and other coffee specialties. In contrast to the earlier used brewing with a Karlsbader Kanne (pot made of porcelain for the preparation of brewed coffee), preparation with an espresso machine is faster.
Working principle
In the espresso machine, water is heated to around 90 ° C in a gas or electrically heated boiler or heat exchanger and passed through finely ground espresso flour under a pressure of around 9 bar. The pressure is generated either by a lever or an electric pump . Systems in which the pressure is generated by water vapor (too high temperature and too low pressure) or a hydraulic device from the line pressure (too high water consumption) are technically outdated.
In order to prevent the coffee grounds from being whirled up in the brewing chamber and thus being over-brewed, the coffee powder is pressed with a tamper , also known as a coffee tamper or espresso tamper . With fully automatic machines, this is done by a stamp, from which the brewing water comes at the same time.
history
Attempts to make espresso with the machine go back to the 19th century when various designs were patented; mentioned are "Lebrun in 1838, Romershausen 1847 and Reiss 1868". Romershausen made experiments with paper, Lebrun offered a steam coffee maker. In all of these attempts, however, the pressure with which the water was forced through the coffee was not sufficient. The repertory of technical literature from 1856 already included more than 60 coffee machines.
In 1938 Achille Gaggia registered a patent in which water was pressed through coffee powder under high pressure using a piston . The official inventor in Italy is Angelo Moriondo, who filed a patent in 1884 that included the use of water and steam. However, the patent was never implemented, which is why it is now assumed that the development of the brand failed. Luigi Bezzera is said to have already shown a prototype at the World Exhibition in Paris in 1855 , but was only able to market it from 1901. Bezzerra's patent was bought by Desiderio Pavoni and further developed together with other inventors.
According to a legend, people were initially surprised that when the pressure was increased, the extracted drink suddenly had a frothy crown, the so-called crema . The espresso drinkers were so skeptical that machine manufacturers initially advertised their espresso as “with natural crema” (Italian: 'con crema naturale') in order not to be suspected of using chemical additives.
From the 1950s onwards there were numerous smaller companies in France and Spain that manufactured espresso machines in addition to Italy. The first German portafilter coffee machine for home use was the Aracati in the 1950s . The Italian devices displaced devices from other countries due to the better price-performance ratio.
Model variants
Professional espresso machines are nowadays used in cafés and, depending on the region, also in the to-go area (petrol stations, stand-up cafes). Fully automatic coffee machines, which according to the definition do not produce "espresso" in the actual sense, are also used in the last-mentioned area, especially because they can be operated without instruction. Machines for home use have become increasingly fashionable in recent years. Among the different types of coffee machines, a distinction is made between the following designs:
Portafilter machines
(often semi-automatic) sometimes work like professional catering equipment with a removable portafilter, which is filled with coffee grounds and fixed in the device using a bayonet lock. They must be supplemented with a separate coffee grinder if the coffee is to be freshly ground and the grinder is not integrated in the device. With these machines, the operator can influence a number of factors that are decisive for the quality of the result: the degree of grinding, the amount and strength of the compression of the coffee grounds in the portafilter and the duration of the brewing time. This makes it possible, with a little practice, to optimally align the process with the quality of the coffee used and to achieve a better result than with a fully automatic machine.
Most portafilter machines work with an electric pump to generate pressure, but there are also models available that use a manually operated lever ( hand lever machines ). The Faema E61, which came on the market in 1961, represents a technological breakthrough, whose brewing group, which was new at the time , recognizable by its characteristic chrome-plated brewing head protruding from the device, is still used in many espresso machines today. The E61 has a spring-loaded chamber integrated in the brewing head for a gentler increase in pressure (pre-infusion), a valve controlled by an eccentric shaft that diverts the residual pressure into the drip tray after the brewing process and, on machines with a heat exchanger, a thermosiphon , which keeps the head hot when stopped and partially protects the water in the heat exchanger from overheating.
Many providers of smaller household models offer portafilter machines that contain a pressure valve in the portafilter or the sieve insert (often called "crema valve", in English mostly "pressurized portafilter" or "pressurized baskets"); this means that the water flow is only released when the pump has built up a pressure of almost 10 bar. The specification 15 bar refers to the theoretical maximum pressure of the pump, which is only reached when the water cannot drain. The correct brewing pressure is around 9 bar, but is set to 12 bar on most household machines. This valve is used to create a crema-like layer on the coffee surface, even when using deposited or even pre-ground coffee, without having to adjust the grind to the machine. However, this “crema” is more of a kind of coffee foam instead of a real emulsion of coffee oils, it dissolves more quickly and has practically no taste of its own. That is why there is often talk of “fake crema”. The same technology can also be found in most standard fully automatic coffee machines.
Centrifuge machines
do not generate overpressure, but have a small centrifuge in which the coffee grounds are located, through which the heated water flows by means of centrifugal force . This type of preparation has the advantage that the machines are much cheaper to manufacture and easier to maintain than automatic machines and high-quality portafilter machines.
Since they delivered an acceptable espresso quality for very little money despite the lack of a brewing pressure of 9 bar, these machines enjoyed great popularity in the lower price segment for a while, but were then largely displaced from the market by the various pad and capsule systems.
Coffee machines
Fully automatic coffee machines can only be regarded as "espresso machines" in the broadest sense, as the correct pressure for preparing an espresso can usually never be achieved. They allow the more or less fully automatic preparation of "strong short coffee" at the push of a button. The fresh brew devices are especially considered to be very user-friendly. However, they only allow a very limited influence on the course of the preparation and thus the quality of the result. In many models, a coffee grinder is integrated so that each portion is freshly ground and brewed, which has a beneficial effect on the taste. With some devices, the brewing unit can be removed and cleaned in a few simple steps, which is optimal from a hygienic point of view. Other machines allow automatic cleaning and descaling, but may be May be more susceptible to mold or other soiling that causes repair costs. Fully automatic coffee machines are sometimes criticized for their high susceptibility to failure and low durability in relation to the often high price. The quality of fully automatic machines lies more in the preparation of café crème or Schümli , but these machines are often unable to produce a “real” espresso based on the Italian model (contrary to what is advertised by the manufacturer). The reason for this is the plastic brewing group , which would not be able to withstand the brewing pressure required for correct espresso preparation. Solid metal brewing groups are almost only found in gastronomic designs.
Outline of professional espresso machines
The names for professional espresso machines differ from those used for home espresso machines.
- Manual or piston espresso machines: This refers to the typical piston machines with portafilter that were common in the 1950s and 1960s. The pressure required to extract the coffee is applied with the help of a piston and a long lever attached to it. Many coffee lovers claim this is the best type of espresso machine. Many manufacturers still produce such machines today (10/2007), but only in small numbers.
- Semi-automatic machines : These differ from piston machines in that the pressure is applied here by an electrically operated pump ( oscillating armature pump or volumetric pump). They have a single switch to operate, with which this pump can simply be switched on and off.
- Fully automatic machines: In the catering industry, this exclusively refers to portafilter machines which - in contrast to semi-automatic machines - measure the amount of water electronically and switch off the pump automatically after a certain amount. As an example of a fully automatic machine, the picture shows a Bistro M32 with a brewing group (manufacturer: Cimbali).
- Super fully automatic machines : These machines did not appear in the catering industry until the mid-1990s. They automate the entire espresso preparation process and have one or more built-in grinders for different types of coffee. The entire process (grinding, pressing, extracting, ejecting the brew) takes place fully automatically at the push of a button. Since the term “fully automatic” was already used, the term “fully automatic” was coined for these more fully automated devices.
- Systems that froth milk fully automatically have existed for a number of years. To do this, milk is sucked in from a container, frothed with air using a jet of steam, heated and fed directly into the cup via a pipe. This system ( cappuccinatore ) can be found in both super-automatic and automatic and semi-automatic machines. The Turbosteam system (from Cimbali), in which the operator only has to place a jug of cold milk under the special nozzle, has been reserved for portafilter machines. At the push of a button, hot steam from the boiler and compressed air from a compressor are injected into the milk until a sensor registers that a set temperature has been reached. If the setting is correct, the foam produced in this way is creamier, finer-pored and at a better temperature than that of a cappuccinatore.
All of these machines are still offered in different group numbers (1 to 5). A group is a unit consisting of a heat exchanger, brewing head, sieve and portafilter (and, in the case of fully automatic machines, a dosing unit consisting of a flow meter, electronics and control panel).
There are various systems for heating water:
- In the early days, almost only single-circuit systems were built in which the brewing water was taken from a large boiler. However, a compromise has to be made between the brewing temperature and sufficient steam volume. (Household machines can be switched from a low brewing temperature to a high steam temperature)
- The most widespread at the moment are two-circuit systems in which water is heated to around 120 ° C in a large boiler (2–20 l), controlled by the steam pressure using a pressostat. Because the boiler is only about two thirds full, a water phase (bottom) and a steam phase (top) form with the resulting steam pressure. Tea water and steam for frothing can be drawn off here through pipes. One heat exchanger per group is embedded in the boiler, which only holds a few hundred milliliters of water and through which the water of the associated brewing group is passed. This means that only fresh water and no boiler water is used for brewing.
- Dual boiler technology has been on the advance for several years. There is a large steam boiler and one or more small brewing kettles, the temperature of which is completely independent of the steam boiler and is very constant.
- Since the boiler has to be preheated for 15 to 30 minutes in boiler machines and the espresso machine should not be permanently switched on for home use, thermoblock espresso machines are enjoying increasing popularity. There is no boiler here, the water is heated directly in an electric instantaneous water heater and conveyed using a vibration pump. Such espresso machines can prepare espresso just two minutes after switching on, but have no brewing pressure control.
The boiler is usually heated electrically. Many gastronomic two-circuit portafilter machines are also available with additional gas heating, which can be connected to weak power connections such as B. at beach bars alone or for the purpose of faster heating from the cold state can also be operated together with the electric heater.
See also
literature
- Dimitrios Tsantidis: The fascination of espresso machines. Franzis, Poing 2008. ISBN 978-3-7723-7049-6
- Richard Steinbrunner: The unofficial espresso machine book: Maintenance and repair of fully automatic coffee machines. Decisive tips for lasting and unadulterated coffee enjoyment . Franzis, Poing 2007. ISBN 978-3-7723-6220-0
- Thomas Leeb, Ingo Rogala: Coffee Espresso and Barista: perfectly prepared . Tomtom, Munich 2002, ISBN 978-3-9808584-0-3
- Andreas Dyballa: Espresso - quality criteria: The influence of varieties, cultivation, harvesting methods, roasting methods, espresso machine technology . VDM, Saarbrücken 2008, ISBN 978-3-639-10373-1
Individual evidence
- ↑ Wingolf Lehnemann, Günter Wiegel man : coffee. Harvesting, roasting, grinding , Münster 2004, p. 109.
- ^ Schubarth (Ed.): Repertorium der Technische Literatur , Arthur Felix, Leipzig 1856, p. 457 f.
- ^ Jimmy Stamp: The Long History of the Espresso Machine. Smithsonian Museum, June 19, 2012, accessed August 22, 2014 .
- ^ Mark Pendergrast, Uncommon Grounds: The History of Coffee and How It Transformed Our World . Basic Books, 2010, ISBN 978-0-465-01836-9 .
