Brew group

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Brew group of a fully automatic coffee machine (DeLonghi EAM series)

A brewing group (also known as a brewing unit ) is a component in fully automatic coffee machines or other coffee machines in which the brewing process for coffee preparation takes place. Depending on the manufacturer, a brewing group can mainly consist of plastic or (apart from the seals) be made entirely of metal. The first removable brew group was developed by Saeco in 1985 .

How the brew group works in a fully automatic coffee machine

The brewing process for a brew group consists of the following steps:

  1. The coffee powder, which is freshly ground per portion by the grinder, falls into the brewing chamber (extraction chamber).
  2. The brewing chamber is moved by a motor in front of the pressure piston.
  3. The brewing chamber and plunger compress the contents.
  4. The required amount of water is pressed into the coffee powder by means of a pump and, after the coffee powder has flowed through, flows out of the brewing group as finished coffee and through the coffee spout into the cup.
  5. The brewing chamber moves back to its original position and the bottom piston pushes out the coffee grounds.
  6. The coffee grounds fall into the coffee grounds container.

cleaning and maintenance

Coffee consists of 10–15% fatty substances which, together with coffee powder residues, settle in the machine over time. The brew group must therefore be cleaned at regular intervals. In devices with a removable brew group (e.g. Saeco , Gaggia , De'Longhi , Nivona, Bosch, Siemens) the brew group is rinsed under warm water, while in devices with a permanently installed brew group (e.g. Jura , Krups) cleaning tablets are used. If the device itself does not provide an automatic cleaning function, the manufacturer usually recommends cleaning the brew group once or twice a week if possible or when the bean container is refilled. Depending on the application, the seals should be changed every quarter to six months and the joints should be serviced with silicone grease.

Capacity

  • Saeco Café, Magic and Royal series:
6-9 g / serving
  • Saeco Incanto series:
6-9 g / serving
  • Jura Z, S, F and E series:
5-16 g / serving
  • DeLonghi EAM series:
7-11 g / serving
  • Eugster (Melitta / Nivona / Miele):
8-14 g / serving

How a manual brew group works

The difference to the automatic brewing group is that here the superstructure of the group with the hot water supply is separated from the coffee powder receptacle, which is implemented in the form of a portafilter with a handle to be inserted into the superstructure. A prominent representative of manual brewing groups is the brewing group, first used in the Faema E61 in 1961, which is now also commonly referred to as the E61 and is still used in traditional espresso machines from various manufacturers. Their function is briefly described below.

The E61 contains a multi-way valve. After clamping a portafilter filled with pressed coffee into the upper part, the valve is switched with a lever (or electrically) so that a connection between the hot water supply (e.g. a boiler or a heat exchanger pipe that runs through a boiler for steam generation) and the brew shower in the upper part, which is arranged directly above the coffee powder, is made. At the same time, an eccentric attached to the lever turns on a switch that drives a pump that pushes hot water from the hot water supply through the coffee under pressure (typically 9 bar). A device for pre-brewing is also built into the E61, in which the water pressure in the coffee chamber is built up with a delay of several seconds so that although hot water already reaches the coffee, the pressure is initially insufficient to push the brewed coffee out of the coffee powder again . After reaching the intended end of the brewing process, the brew shower is disconnected from the hot water supply by turning the lever and at the same time the valve is switched so that water that is still under pressure in the coffee chamber can flow out in a drain. During periods of non-use, a passive (convective) hot water circuit is also created through the brewing group so that it cannot cool down.

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