How Does Machine Espresso Work?
The machine espresso is made using precision pressure, and filter technology that is awe-inspiring to make the coffee you enjoy. What exactly is it?
In order to make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee but the difference is in the pressure.
The Group Head
The group head is the portafilter that is inserted when you are making espresso. It disperses the water into the portafilter and regulates the pressure of extraction. There are many different types of group heads each with distinct advantages and drawbacks. Some are specifically designed for the stability of temperature while some are designed to handle pre-infusion. Some are designed to control the lever. There are some that have a combination of features, like the E61 one, which is the most popular choice among baristas due to its capacity to offer multiple benefits in one package.
As you can see from the above photo the head of the group is fitted with several notches. The portafilter is placed in these notches, then twist the head to lock it. A rubber gasket is located in the notches to create a seal when you insert your portafilter. The notches allow for an exact placement of the portafilter. This is vital for a consistent extraction.
The group head is not just able to allow the portafilter to be inserted easily, but it also maintains an even temperature. This is done by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is at the right level to extract the coffee. It is important to note that even a tiny variation can mean the difference between a great and a great espresso.
The Pump
The motorized pumps used in espresso machines rotary provide nine atmospheric bar pressure required to extract espresso. This differs from manually operated piston machines that employ levers. This pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger before being pushed through the ground coffee in the group head.
Pumps are typically less expensive than piston-driven machines and tend to last longer, however both types of machines may be damaged by excessive use and inadequate cleaning. Pumps are also more complex mechanically, which could increase the cost of even the simplest models.
Some espresso machines employ steam pressure instead of a pump for brewing espresso. This can result in over-extraction because the boiler that produces steam also heats the water to boil. The machines also need to continually rebuild their pressure between cups. This requires energy and time.
Many espresso machines utilize the rotary or vibration pump, which has a vibration model using a vibrating disc to generate the pressure, and rotating models that push hot water through the grounds at high speed. Both models can produce an excellent espresso, however Rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the component which heats the water to the ideal temperature to extract. The steam produced reaches the portafilter, which holds the Salter EK4369 Barista Pro Espresso Maker 15Bar grounds. It is then pumped into the cup. During this process, the steam creates pressure to push through the coffee grounds. This results in a crema on the top of the espresso. This is a hallmark of a good De'Longhi Stilosa EC 230.BK Espresso Machine Black (written by Coffeee).
There are three kinds of espresso machines, each with different pumps and the temperature of the brew. There are various ways to control the amount of brew, as well as the size of cup that can be produced by the machine.
The first espresso machines were steam-type. They utilized one boiler to create both steam and brew, however the pressure they were able to produce was very low - just two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.
The most popular espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they picture these machines. Semi-automatic machines require you to grind and tamp the beans by yourself The pump, however, regulates the water flow and pressure. This is an excellent compromise between human touch and the mechanised consistency.
The Filter
Typically, espresso machines have filters to separate the grounds of the coffee as they go through the hot water. The filter is also a vital component of the temperature control system as it prevents the machine from overheating.
Filters also aid in flavor, as it permits a longer flowering period. This lets the beans let their nuances out, and allows for better extraction.
It is important to remember that even the finest filter can produce a bad cup of coffee. The quality of the beans as well as the extraction, are still very important.
This is where the magic happens, it's the thing that makes an espresso really taste good. The grouphead, sometimes referred to as the brew head, is where the portafilter (the thing you put the coffee ground into) is placed when you're making espresso.
Steam-driven espresso machines use hot water that is heated inside an airtight vessel to create steam. The steam then pushes hot water into the grounds of the coffee under pressure. These machines are less expensive and easier for the owner to maintain than pumps-driven models. They are however limited to create 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, compressed air-pump-driven espresso machines have become more popular. They make use of an air compressor to push hot water through the ground, and are more mobile than electric steam-driven espresso machines.