How Does Machine Espresso Work?
Machine espresso uses precision pressure and mind-blowing filter technology to make the perfect cup of coffee. What exactly is it?
In order to make espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee, but the major difference is in the pressure.
The Group Head
As the name suggests the group head is where you put your portafilter in when making espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure of the extraction. There are a variety of types of group heads each with its particular advantages and disadvantages. Some are designed to provide temperature stability while others are built to handle pre-infusion. Others are made to control the lever. Some come with a combination of both, such as the E61. This is a very popular choice for baristas since it provides multiple advantages in one package.
As you can see from the image above the head of the group has a number of notches. You can place your portafilter inside these notches, and then twist the head to secure it. A gasket made of rubber is positioned inside the notches, which helps create a seal while you insert your portafilter. The notches on the head allow for a precise positioning of the portafilter which is essential to ensure a consistent extraction.
In addition to allowing you easily connect your portafilter, the group head is also responsible for maintaining a consistent temperature. It does this by circulating hot water through the brew basket and around the portafilter to ensure that it is always at the right temperature to extract. This is important because even a
best small espresso machine difference in temperature can make the difference between a good and great espresso.
The Pump
Unlike manual piston machines, which rely on a lever to pressurize water, rotating espresso machines rely upon motorized pumps to deliver the nine atmospheric bars of pressure that are required for espresso extraction. This pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger prior being pushed through the ground coffee inside the group head.
Pumps tend to be cheaper and last longer than piston-driven machines. However, both types of machines are susceptible to degrading due to excessive use and insufficient cleaning. Pumps are also more complicated mechanically, which can increase the cost of even most basic models.
Some espresso machines use steam pressure instead of a pump to brew espresso. The disadvantage of this is that the boiler that produces steam also increases the temperature of water until it reaches boiling which could lead to over-extraction. In addition these machines are often required to rebuild their pressure between cups, which requires time and energy.
Many espresso machines employ either a rotary or vibration pump, which has a vibration model using a vibrating disc to generate the pressure and a rotary model pushing hot water through the grounds at high speed. Both machines produce great espresso, but rotary machines are quieter, more durable and less likely to fail.
The Boiler
The boiler is the part that heats water to the ideal temperature for extraction. The steam that is produced gets to the portafilter which is the container that holds the espresso coffee grounds. It is then poured into the cup. During this process the steam creates enough pressure to push the grounds of the coffee through. This produces a layer of crema on top. This is one of the hallmarks of a good espresso.
There are three kinds of espresso machines, each having a different type of pump and the temperature of the brew. There are different ways to control the brew and the size of cup that can be produced by the machine.
The earliest
espresso machine sale machines were steam type. They employed one boiler to make steam and brew, however the pressure they were able to create was minimal - two bars of atmospheric pressure, at most. This led to the coffee tasting burnt and bitter. The modern
espresso machine was designed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most commonly used espresso maker is a semi-automatic one with an electric pump. These are the images people have when they think of an espresso machine. With a semi-automatic
compact espresso machine machine, you must grind the beans and tamp them by hand. However, the pump controls the flow of water and pressure. This is a great compromise between the human touch and the mechanized quality.
The Filter
Typically, espresso machines utilize filters to separate the grounds of coffee when they pass through the hot water. The filter is also an essential part of the machine's temperature control, since it stops overheating.
A filter also helps with flavor because it allows for the beans to flower for a longer period of time. This helps the beans release their flavor and gives an opportunity to improve extraction.
However, it is important to keep in mind that even a top filter can make a terrible cup of coffee, because the quality of the beans and extraction are crucial.
It's in this area that the magic takes place. This is the reason why espresso tastes so good. The grouphead, sometimes referred to as the brew head, is where the portafilter (the thingy you put the coffee grounds into) is placed when you're making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight container to produce steam, which is then pushed through the grounds at high pressure. These kinds of machines are usually less expensive and simpler to maintain than pump-driven models. They are however limited in their ability for creating the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.
In recent years, espresso machines powered by a compressed air pump have become increasingly popular. They utilize an air compressor to push hot water through grounds and are much more portable than electric steam-driven machines.