The Espresso machine
and espresso coffee is becoming increasingly popular throughout the
world.
The Italian word ‘espresso’ can literally be translated as
‘express’, which is no doubt why the term ‘expresso’ is often
mistakenly used. To all intents and purposes, the modern use of the
word ‘espresso’ is understood everywhere to describe a coffee
beverage produced by forcing pressurised hot water through tightly
packed fine ground coffee into a small cup. The result is a very
strong coffee with a characteristic ‘crema’ – a reddish brown foam
that floats on the surface.
Whilst it is claimed that the first espresso coffee was made in
France in 1822, the patent for the first modern-day espresso
machine was applied for by an Italian Achille Gaggia in 1938. His
system utilised a spring powered lever system to force the water
through the coffee grounds. The first pump driven espresso machine
was produced in 1960 by the Faema company. Machines come with
various numbers of brew points called ‘Groups’, and the handles
holding the metal filter baskets which contain the compressed
coffee are called Group Handles.
steam, piston or
pump
Espresso machines come in steam, piston (or lever) and pump
driven varieties.
A steam-driven unit operates by forcing water through the coffee
using steam or steam pressure. The first espresso machines were of
this type, and the design is still used today in low-cost domestic
machines, as very few moving parts are required.
The piston or lever-driven machine was developed and built in 1947
by Achille Gaggia and his company in Italy. This design uses a
piston or lever to pressurise hot water and send it through the
ground coffee. The act of producing a cup of espresso from this
system is generally termed pulling a shot, because the machine
requires pulling a long handled lever to produce a shot of
coffee.
There are, in fact, two types of piston or lever machines – those
fitted with a manual piston and those with a spring piston. With
the manual piston, the operator pulls the lever to send the water
directly through the ground coffee. In the spring piston design,
the operator pulls the lever which works to tension a spring, which
in turn delivers a steady pressure for the water (usually 8 to 10
bar) to be pushed through the coffee. The piston-driven machine was
the first to produce the crema on a cup of espresso, which was
originally thought to be undesirable. This coffee crema is now
considered characteristic of a properly made quality cup of
espresso.
An innovation to the basic piston-driven design is the pump-driven
machine. This has become the most popular design in commercial use,
as instead of needing manual operator force, a motor driven pump
provides the necessary work to force the water through the ground
coffee
Domestic espresso machines typically use just 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
less than the temperature for creating steam, the machine requires
time to make the transition from one mode to the other. Better
quality machines use the boiler chamber only for making steam, and
the water for brewing most commonly passes through a heat exchanger
(taking some heat from the steam, without rising to the same
temperature). Most domestic espresso models can be either piston or
pump-driven, but to get one to that offers all the basic
requirements of good espresso coffee production means they are, by
necessity, very expensive.