A Productive Rant About Machine Espresso
How Does Machine Espresso Work?
Machine espresso uses precision pressure and incredible filter technology to produce the perfect cup of coffee. How exactly does it work?
In order to make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However, it is the pressure that makes the main difference.
The Group Head
The group head is the portafilter that you place in the espresso maker when making it. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the extraction. There are many different types of group heads each with distinct advantages and disadvantages. Some are focused on temperature stability, others on pre-infusion options, and others are designed to control the lever. Some include a combination like the E61. This is a favorite among baristas since it provides multiple benefits in one package.
As you can see in the image above the group head comes with several notches to place your portafilter and then twist it with your hands to lock it in. A gasket of rubber is situated inside the notches to help create a seal while you insert your portafilter. The notches allow for precise placement of your portafilter. This is crucial to ensure an efficient extraction.
The group head not only lets you to insert your portafilter easily however, it also keeps the same temperature. It does this by circulating hot water through the brew basket and around the portafilter, making sure that it's always at the correct temperature for extraction. This is important because just a few degrees could make the difference between a excellent and great espresso.
The Pump
Motorized pumps in espresso machines rotary provide nine atmospheric bar pressure needed to extract espresso. This is different from manual piston machines that rely on levers. This pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to being pumped through the ground coffee in the group head.
Pumps tend to be less expensive and last for longer than piston-driven machines. However, both types of machines may degrade due to excessive use and poor cleaning. Pumps are also more complex mechanically, which could increase prices of even simplest models.
Some espresso machines use steam pressure instead of a pump to brew espresso. This could lead to over-extraction since the boiler that makes steam also causes the water to boil. These machines also have to constantly rebuild their pressure between cups. This takes energy and time.
Many espresso machines utilize a vibration or rotary pump, which has a vibration model using a rotating disc that generates the pressure and rotating models that push hot water through the grounds at high speed. Both types of machine can produce an excellent espresso, but the rotary models are quieter and more durable than vibration pumps.
The Boiler
The boiler is the component that heats water to an optimal temperature for extraction. The steam created is then directed to the portafilter, which contains the espresso coffee grounds. The steam is then channeled into the cup. During this process, the steam creates pressure that pushes through the coffee grounds. This results in a layer crema that is then poured over. This is a sign of a great espresso.
There are three types of espresso makers , which differ in the kind of pump they use and how hot the espresso is. There are a variety of ways in which the brew can be controlled as well as the dimensions of the cup the machine can produce.
The first espresso machines were steam-based. They utilized one boiler to create both brew and steam, however the pressure they were able to produce was very low - just two bars of atmospheric pressure, at most. This led to the coffee tasting bitter and burnt. This is the reason Milanese producers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.
The most popular espresso maker is a semi-automatic machine with an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic machine you must grind the beans and then tamp them by hand. The pump is able to regulate the flow of water and pressure. This is a great combination of human control and mechanized consistency.
The Filter
Typically, espresso machines use a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also a vital element of the machine's temperature control, since it stops overheating.
A filter can also help with flavor because it allows for a longer flowering period. This allows beans to let their nuances out and provides the chance for better extraction.
It is important to keep in mind that even the best filter can result in a bad cup of coffee. The quality of the beans, as well as the extraction, remain vital.
This is where the magic happens, it's what makes espresso taste great. The grouphead (also called the brewhead) is where you place the portafilter, which is the thingy used to place the grounds of coffee into when making espresso.
Steam-driven espresso machines make use of hot water that is heated in an airtight container to create steam. The steam then pushes hot water through grounds of coffee under high pressure. These machines are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited for creating the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent years, compressed-air-pump-driven espresso machines have been gaining popularity. They utilize an air compressor to push the hot water through the grounds and are much more portable than electric steam-driven machines.