How Does Machine Espresso Work?
Machine espresso employs precise pressure and incredible filter technology to produce the perfect cup of coffee. What exactly is it?
Espresso is produced by pushing hot water under pressure through finely ground coffee. The process is similar to making drip coffee. However the pressure is the major difference.
The Head of the Group
The group head is the portafilter that you insert when brewing espresso. It is responsible for dispersing water into the portafilter, and controlling the pressure of the resulting extraction. There are many different types of group heads each with distinct advantages and drawbacks. Some are designed for stability of temperature while others are specifically designed to handle pre-infusion. Others are built to control the lever. Some come with a combination of both, such as the E61. This is a preferred choice for baristas as it provides a variety of benefits in one package.
As you can see from the photo above the group head is fitted with several notches. You place your portafilter inside these notches, and then twist the head to lock it. A rubber gasket is located inside the notches, which helps create a seal when you insert your portafilter. The notches on the head allow for a precise location of the portafilter which is essential for a consistent extraction.
The group head is not just able to allow the portafilter to be inserted easily however it also keeps an even temperature. This is done by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is constant for extraction. It is crucial to keep in mind that even a small variation can mean the difference between a great and a excellent espresso.
The Pump
In contrast to piston machines that are manually operated, which use a lever to pressurize water, rotating espresso machines rely upon motorized pumps that provide the nine atmospheric bars of pressure that are required for espresso extraction. This pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger before being pumped through the ground coffee inside the group head.
Pumps are typically less expensive than piston-driven machines and tend to last longer. However, both types of machines can become damaged due to excessive use and poor cleaning. They also add mechanical complexity that can lead to an expensive price for even the most basic models.
Some espresso machines do away with the pump entirely and utilize steam pressure to make espresso. The drawback of this is that the boiler that produces steam also increases the temperature of the water until it reaches boiling, which can lead to excessive extraction. In addition these machines typically have to restore their pressure between cups, which takes time and energy.
Many espresso machines make use of a vibration or rotary pump, which is a vibration model using a vibrating disc to create pressure and rotating models that push hot water through the grounds under high speed. Both types of machines can make excellent espresso, but rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the element that heats water to an ideal temperature to extract. The steam that is produced reaches the portafilter which holds ground espresso beans and is then pumped down into the cup. During this process, the steam creates pressure and pushes through the grounds of the coffee. This produces a layer of crema that is then poured over. This is one of the main characteristics of a great espresso.
There are three types of espresso machines, each with distinct pumps and the temperature of the brew. There are many ways to control the strength of the brew and the size of cup that can be made by the machine.
The first espresso machines were steam-type. The first espresso machines were steam-type machines. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was designed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso maker is a semi-automatic device that has an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp your beans yourself however the pump controls the water flow and pressure. This is a great compromise between the human touch and mechanized consistency.
The Filter
Espresso machines typically use filters that separate the grounds of the coffee from hot water. The filter is also an essential part of the temperature control system, as it keeps the machine from overheating.
It also helps with flavor, as it allows for a longer bloom phase. This allows beans to release their flavor and gives the chance for better extraction.
However, it is important to keep in mind that even a top filter can make a terrible cup of coffee, as the quality of the beans and extraction is still crucial.
It's in this area that the magic takes place. This is what makes espresso taste so good. The grouphead, sometimes called the brew head, is where the portafilter (the thingy you put the coffee ground into) is placed when making espresso.
In a steam-driven espresso machine hot water is heated in an airtight container to create steam. This then pushes the hot water through the grounds at a high pressure. These kinds of machines are generally less expensive and easier to maintain than pump-driven models. However, they are not as efficient in their ability to provide the ideal conditions for brewing since they operate at 1-1.5 bars of pressure. coffee and espresso maker requires 9-10 bars.
In recent years, espresso machines driven by a compressed air pump have become increasingly popular. They utilize an air compressor to force hot water into the grounds, and are far more portable than steam-driven electric machines.