9 Things Your Parents Teach You About Machine Espresso
How Does Machine Espresso Work?
Machine espresso uses precision pressure and amazing filter technology to make the delicious coffee we enjoy. What exactly does it work?
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 Head of the Group
As the name implies the group head is where you place your portafilter while making espresso. It is responsible for dispersing water into the portafilter and controlling the pressure that results from the extraction. There are a variety of group heads each with their own advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion features, and others are designed to control the lever. Some include a mix of features, such as the E61 that is the standard choice for many baristas due to its capacity to provide multiple benefits in one package.
As you can see in the picture above the group head is fitted with several notches. You place your portafilter in these notches and then turn the head around to secure it. A gasket made of rubber is positioned in the notches to create a seal while you insert your portafilter. The notches on the head permit an exact location of the portafilter which is necessary to ensure an even extraction.
Apart from allowing you easily connect your portafilter, the group head is responsible for maintaining a consistent temperature. This is accomplished by cycling hot water around the portafilter, and through the brew basin, ensuring that the temperature is constant for extraction. This is important because just a few degrees could make the difference between excellent and great espresso.
The Pump
The motorized pumps that are used in rotary espresso machines provide the nine atmospheric bars of pressure required for espresso extraction. This differs from manual piston machines that use a lever. The pressure builds up by removing 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 are typically less expensive and last for longer than piston-driven machines. However, both types of machines may degrade due to overuse and inadequate cleaning. They also add mechanical complexity and can lead to costly prices for even the simplest models.
Certain espresso machine with frother machines can eliminate the pump entirely and utilize steam pressure to make espresso. This can lead to over-extraction as the boiler that makes steam also heats the water until it comes to a boil. The machines also need to continuously rebuild their pressure between cups. This takes energy and time.
Many espresso machines make use of either a rotary or vibration pump, with a vibration model using a vibrating disc that generates the pressure, and an rotary model that pushes hot water through the grounds at high speed. Both machines can make great espresso however rotary machines tend to be more quiet, durable and less likely to break down.
The Boiler
The boiler is the element that heats water to the ideal temperature to extract. The steam produced is then directed to the portafilter, which is the container that holds the espresso coffee grounds. The steam is then channeled into the cup. During this process the steam causes enough pressure to push the grounds of the coffee through. This creates a layer crema on top. This is a hallmark of a great espresso.
There are three types of espresso machines, each having distinct pumps and brew temperature. There are a variety of ways in which the brew could be controlled, as well as the size of the cup that the machine is capable of making.
The first small espresso machine machines were steam types. They used only one boiler to make both brew and steam, however, the pressure they could create was minimal - two bars of atmospheric pressure maximum. This resulted in the coffee tasting bitter and burnt. This is the reason Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.
The most commonly used espresso maker is a semi-automatic machine with an electric pump. When people think of espresso machines, they think of these machines. If you have a semi-automatic machine you must grind the beans and tamp them by hand. However, the pump provides regulated water flow and pressure. This is a fantastic solution that combines human control with mechanised reliability.
The Filter
Espresso machines usually have a filter that separates the coffee grounds from the hot water. The filter is also a vital component of the machine's temperature control, as it helps prevent overheating.
A filter also helps with flavor because it allows for a longer flowering period. This allows the beans to release their nuances and gives an opportunity to improve extraction.
However it is crucial to remember that even a good filter can produce a bad cup of coffee as the quality of the beans and extraction are important.
It's in this area that the magic happens. This is what makes espresso taste so good. The grouphead, sometimes called the brewhead, is where the portafilter (the device you put the coffee ground into) sits when you're making espresso.
Steam-driven espresso machines make use of hot water heated in an airtight container to make steam. The steam then pushes hot water into the coffee grounds under high end espresso machine pressure. These kinds of machines are generally less expensive and easier to maintain than pump-driven models. They are however limited in their ability to create the perfect conditions for brewing since they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent years, espresso coffee machine with milk frother machines powered by compressed air-pump have become increasingly popular. They utilize an air compressor to push hot water into the grounds and are much more portable than steam-driven electric machines.