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Espresso is a small but mighty drink that has a significant impact on people’s mornings. A properly made espresso shot has a rich, dark crema that sits atop the liquid like a beautiful crown. The crema is the result of emulsified oils and proteins that have been extracted from the coffee beans during the brewing process. To achieve this level of perfection, baristas must apply the perfect amount of pressure to the espresso grounds.
Espresso machines, especially those marketed to home baristas, can mislead consumers about the minimum requirements to buy a machine by. It is important to know what really matters when picking out an espresso machine and what is marketing fluff.
Why is proper pressure important for optimal espresso shots? Too little pressure and the espresso will be weak and watery. Too much pressure and the espresso will come out too quickly, resulting in a burnt or bitter taste.
Pressure on espresso machines is measured by bar. When talking about plural numbers, it is still correct to reference the unit of measure as 'bar' instead of 'bars'. The ideal pressure for an espresso shot is 9-bar, which can be achieved using a quality espresso machine.
The thing that sets pulling espresso shots apart from other coffee brewing methods is the unique use of pressure. It makes sense that getting the right amount of that pressure is one of the most important aspects of pulling a shot. Again, the ideal pressure for an espresso shot is 9-bar, which produces a perfect balance of flavor and extraction. Too much more than 9-bar can result in a burnt-tasting espresso, while too less than 9-bar will produce a weak and overly bright shot.
When pulling an espresso shot, the barista should always start by achieving the recommended 9-bar of pressure. Experimentation is perfectly fine when testing out the optimal pressure for a particular coffee.
Adjustable pressure is good for in-the-moment corrections as well. If the shot seems to be taking too long, you can slowly increase the pressure to coax the shot out. However, if the shot is coming out too quickly or tastes burnt, you should back off on the pressure.
TheCASABREWS 5700GENSE All-in-One Espresso Machine is an example of an espresso machine with a higher bar pressure advertised. It goes up to 20-bar with its Italian pressure pump. But why go above 9-bar?
The first reason to have a machine able to supply more pressure is for precision. The coarseness of the coffee grounds and the level of the tamp in the portafilter can affect the amount of pressure needed. It is nice to have something that can put out a little more pressure when you need it to. To dial in the perfect pressure output for your shot, you'll want to perfect the amount of coffee grounds you use and your tamping.
The second reason to have an espresso machine capable of slightly higher bar pressure is for the ongoing reliability of the machine. If a pump could only handle 9-bar and was constantly maxed out with the average espresso shot the pump could die out quicker. Having a pump that can handle more than the average pressure is nice to have as it ensures that the pump can last.
The third reason is that the advertised pressure of the machine is usually the pressure at the pump. Espresso machines are designed to apply a certain amount of pressure to the coffee grounds to ensure proper extraction. The pressure at the pump is typically around 15-bar. This high pressure is necessary to force the water through the coffee grounds and produce a flavorful espresso shot.
However, the pressure inside the espresso machine is not always constant. As the water flows through the coffee grounds, the pressure will drop. This is due to resistance from the coffee grounds themselves. To compensate for this, some espresso machines have a built-in mechanism that automatically increases the pump pressure as needed.
So, what does all this mean for you? If you're making espresso at home, it's important to pay attention to both the pump pressure and the ground pressure. Having an espresso machine that can output up to 20-bar is important because it can handle the regular load of pulling shots plus it takes more than 9-bar of pump pressure to apply 9-bar of pressure on the coffee grounds.