While lots of devices claim to be espresso equipment, there are only two sorts that can really deliver café-quality espresso, the piston-lever apparatus and the electric pump machine. The piston-lever machine depends upon hand-operated mechanical force to create the extraction pressure. Successful operation calls for experience and skill, and in general, the piston-lever technique is very much a niche, specialty item used by purists. The electric pump espresso apparatus produces 99.9% of the world’s café-quality espresso.
Among the devices claiming to be espresso machines, many types do not produce the process needed for authentic espresso extraction. The most universal of these devices is the “steam” espresso machine that depends on a boiling chamber to generate steam pressure for brewing. However, because the steam force is too low and the temperature is too hot, it burns the coffee and extracts disagreeable bitter oils. After the steam has dispersed, the user must reiterate the sequence, taking several minutes, to churn out further drinks.
ELECTRIC PUMP ESPRESSO MACHINES
The main components of the pump espresso machine are: (1) Water Reservoir (or Water-Line Connection); (2) Pump; (3) Boiler (or Thermal Block); (4) Brew Handle (Portafilter); and (5) Steam Pipe (used to heat and froth milk).
As any electromechanical device, a pump espresso machine will differ in terms of dimension, performance, construction, materials, and convenience features. However, the pump machine will include some use of all of these workings that take part in the following steps in the brewing process:
Water for the brewing process is supplied by a water reservoir (for home machines) or by a water line (for numerous commercial units). The pump, either a vibration pump or a rotary vane pump, provides the brewing pressure and is set generally at 15 bar. A boiler or thermal block heats the water to 195°F for use in the extraction process. Upon activation of the pump, the heated water flows through a filter screen in the brew head and is forced through the coffee enclosed in a finely perforated steel basket held by the portafilter. In order to make the necessary resistance for good extraction, the coffee ought to be finely milled and evenly tamped or packed. The fluid, now containing tasty colloidal oils extracted from the coffee, passes through one or two spouts on the underside of the portafilter into one or two preheated ceramic cups.
If the above process takes place, using fresh coffee, of course, the ensuing espresso drink will be topped by a quarter-inch layer of golden foam, known as the crema. The crema is soft, creamy, and intense in bittersweet taste cherished as the mark of a good espresso and savored by coffee connoisseurs around the globe.
After brewing a shot, if the electric pump espresso apparatus is without delay prepared for the next shot; this is frequently referred to as “zero recovery time”.
A proper espresso machine can create steam for heating and frothing milk used in espresso-based beverages such as cappuccino and caffè latte. In a domestic machine, the boiler or thermal block heats water to steam at 250 to 270°F that is then released through the steam arm by manually opening a valve. Numerous commercial units can brew espresso and produce steam simultaneously because of a double-boiler configuration.
Comfort features found amid assorted styles of espresso machines include volumetric controls, pressurized portafilters, frothing attachments, and cup warming surfaces.
SUPERAUTOMATIC COFFEE MACHINES
The most advanced electric pump machines are wholly automatic and are known as superautomatic coffee machines. At the touch of a button, a superautomatic coffee machines goes from bean to cup. In other words, the superautomatic espresso machine grinds the beans, doses, tamps, extracts, and dispenses the shot of coffee into the cup. The depleted coffee is expelled mechanically into a self-contained “dump” bin. The brewing process is controlled by a microprocessor and involves additional components such as a burr grinder, dosing device, and a mechanical brew group (in place of the brew head and portafilter).