For some, espresso is more than a morning fix — it’s an art form. Crafting a great cup of espresso requires attention to detail but also a keen understanding of the unique and delicate balance between pressure and flavor.
The perfect shot of espresso has to be “just right”: Too much pressure can create an overly bitter cup that’s hard to swallow, yet too little pressure will leave you with nothing more than a watery mess.
Navigating the world of espresso pressure can be tricky and often needs careful changes in grind size, temperature, tamping, and more. When done right, it results in an incredible and flavorful experience sure to make even the most devoted coffee lover dance with delight!
So, what’s the best pressure for espresso extraction? Let’s find out.
Pressure: The Secret Ingredient in Espresso?
The critical factor when making espresso is, of course, pressure. It’s what forces the water through the coffee grounds and extracts all those lovely flavors that we enjoy so much.
Espresso is made by forcing hot water, under high pressure, through tightly packed coffee grounds. This process extracts the coffee’s flavor compounds, oils, and caffeine – everything that makes espresso so delicious.
The pressure used during extraction has a tremendous impact on the final flavor of the espresso. But before we get into that, let’s look at how pressure is generated in the first place.
How Is Pressure Generated in an Espresso Machine?
Espresso machines generate pressure in one of two ways: either with pump pressure or with steam pressure. Pump-driven machines are more common because they generate more consistent pressure than steam-driven machines.
Pump-driven espresso machines have an electric pump that forces water through the coffee grounds. The pump generates the pressure, which can reach up to 15 bars (217 psi).
On the other hand, steam-driven espresso machines use steam (kinda obvious) to generate pressure. The water is heated until it turns to steam, and this steam is used to force the water through the coffee grounds.
The pressure generated by steam is much less consistent than that of a pump-driven machine. It can range from 2 bars (29 psi) to 8 bars (116 psi), depending on how well the machine is maintained and the quality of the espresso beans used. Moka pots are a type of steam-driven espresso machine.
Now that we know how pressure is generated let’s look at how it affects the espresso flavor.
How Does Pressure Affect Espresso Flavor?
Drawing from our experience, we know that the brewing pressure used during extraction significantly impacts the espresso’s final flavor. The reason for this is that flavors are extracted at different pressures.
Some flavors are extracted quickly and easily, even at low pressure, while others require higher pressure to be extracted from your favorite coffee beans. For example, bitter compounds are extracted more easily than sweet compounds.
The espresso will be bitter if you use too much brew pressure during extraction. On the other hand, if you use too little pressure, the espresso will be more acidic and sour.
How much pressure is used can also affect the texture of the espresso? If the pressure is too low, the espresso will be thin and lack body. If the pressure is too high, the espresso can become thick and have an unpleasant body and mouthfeel.
What is Pressure?
Pressure is simply the force exerted by a fluid on a surface. In the case of espresso, the fluid is water, and the surface is the coffee grounds. The higher the pressure, the more force exerted on the coffee grounds and the more flavor extracted from the beans.
Calculated by the force exerted perpendicular to the surface area of an object per unit area, pressure is typically measured in pounds per square inch (PSI). However, you will almost always hear it expressed in bars for espresso.
A bar is a unit of pressure equal to 100,000 Pa (pascals), or about 14.5 PSI. The creation of the bar and millibar came from Norwegian meteorologist Vilhelm Bjerknes, who is now known for his advances in modern weather prediction.
How Does Pressure Affect Espresso Quality?
The ideal pressure for brewing espresso is around 9 bars or nine times the atmospheric pressure at sea level. This may not seem like a lot, but it’s actually more than you might think.
Most car tires hold about 32 pounds per square inch (PSI) of air, while bicycle tires can be inflated to as high as 65-85 PSI. Nine bars of pressure is the equivalent of 130 PSI – four times more than a car tire!
Simply put, pressure affects espresso because it affects the number of soluble compounds pulled out of your coffee grounds. Solubility is the amount of compounds that will dissolve.
As you increase the pressure, the collision frequency increases, and thus the total compounds extracted increase. As you decrease the pressure, your extracted compounds go down.
Some flavors are extracted quickly and easily, even at low pressure, while others require higher pressure to be extracted. For example, sour compounds are extracted more easily than sweet compounds.
If you want to extract more flavor from your coffee grounds, you need to maintain pressure for a sufficient time. This is why espresso has such a unique flavor – the pressure extracts more coffee flavors than any other brewing method.
What makes espresso special?
Espresso is unique because it requires ultra-fine ground coffee and a short extraction time. These two factors work together to create a concentrate that is full of flavor.
The ultra-fine grind exposes more of the coffee’s surface area to the water, allowing more flavor extraction. The short extraction time prevents the coffee from becoming bitter or over-extracted.
Modifying the temperature, grind size, and extraction time can change the flavors pulled out of the coffee. For example, a longer extraction time at a lower temperature is called a Lungo. Alternatively, a Ristretto is made with an even finer grind size, less water, and a shorter extraction time.
How to Adjust the Pressure for Espresso
Now that we know how pressure affects espresso, let’s talk about adjusting the pressure to get the perfect shot. The first thing you need to do is make sure your espresso coffee machine can produce the desired pressure.
Some espresso machines have a pump that allows you to adjust the pressure, while others have a fixed pressure. If your device has a pump control setting, you can turn it up or down to increase or decrease the pressure. If your machine has static pressure, you must adjust the coffee grind size or coffee extraction time to compensate.
If your machine has a fixed pressure setting, you can buy special portafilter gadgets and adaptors to create more pressure. These are often used by professional baristas to fine-tune their espresso shots.
Adjusting espresso Time
Along with pressure and grind size, time is a huge factor. A standard shot is between 25 – 35 seconds. That may not seem like a lot of time, but it’s significant when brewing espresso.
If you want to adjust the time, you can change the grind size or the flow rate. A finer grind will require less time to extract the same amount of flavor, while a coarser grind will take longer. If the grind is too fine, this can create backpressure and even prevent water from penetrating your beans.
Different roast levels also require different extraction times. A light roast will require more time than a dark roast because the light roast is less porous and has less surface area exposed.
Another way to adjust the flow rate is by changing the size of your espresso shots. For example, a double shot will take longer to extract than a single shot. The quantity of coffee grinds will also affect the flow rate and extraction time.
If you want to get really technical, you can also use a refractometer to measure the Total Dissolved Solids (TDS) in your espresso shots. The TDS measures the coffee’s concentration and is directly related to extraction time and temperature.
A higher TDS means more particulates have been extracted from the coffee and vice versa. By measuring the TDS, you can fine-tune the extraction time to get the perfect shot of espresso every time.
Does pressure affect espresso crema?
Crema is that lovely, creamy foam that sits on top of a freshly brewed espresso. It’s made up of coffee oils and brewing gases that are released during extraction.
While pressure does affect crema production, it is not the only factor. The grind size, extraction time, and water temperature all play a role in crema formation. Also, the beans themselves play a massive role. Different types of beans will produce different amounts of crema.
In general, a darker roast will produce more crema than a lighter roast. This is because the darker roasts have less moisture and, therefore, a higher oil concentration. The oils are essential for crema production.
So, to answer the question, yes – pressure does affect espresso crema. But it’s not the only factor that you need to consider.
Brewing the perfect shot of espresso can be difficult, but with patience and practice, it is definitely achievable. By understanding how pressure, grind size, extraction time, water temperature, and roast levels affect your espresso shots, you will be able to create delicious coffee drinks every single time.
With these tips in mind, you will feel confident about making fantastic espressos for yourself or your favorite coffee-loving friends and family!
So get out there and start brewing!