The Power Behind the Perfect Cup: Exploring the Influence of Pressure on Espresso Extraction

Are you tired of settling for mediocre espresso? Do you long for that perfect, rich crema and an explosion of flavor? Well, my caffeine-loving friend, you've come to the right place. Today, we're diving deep into the world of espresso brew pressure and uncovering the secrets behind the best espresso machine pressure for that heavenly cup of joe. From understanding the impact of pressure on extraction to unraveling the mysteries of 15 bar pumps, we'll cover it all. So grab your favorite mug and get ready to embark on a journey to espresso nirvana.

Understanding espresso brew pressure

Before we delve into the findings, I'd like to provide a brief explanation of pressure.

In modern espresso machines, water is forced through the ground coffee using an electric pump that operates at a specific pressure. The pressure is typically measured in bars. To give you some context, when you turn your tap on full at home, you're likely getting a pressure of 3-4 bars. So, the pump in an espresso machine increases the pressure by 2-3 times that level.

To put it in perspective, 9 bars of pressure is equivalent to diving 90 meters deep underwater, assuming you're familiar with how that feels.

Older lever machines use a lever, a spring, and the strength of the barista to create this pressure.

espresso pressure lever machine

A lever machine is a simple example of what baristas refer to as "pressure profiling." This term refers to the process of manipulating the water pressure during the espresso extraction. Unlike electric pumps, which maintain a constant pressure, lever machines begin with high pressure that gradually decreases as the spring returns to its original position.

Another example of pressure manipulation is pre-infusion. This involves using low-pressure water for the initial few seconds to moisten the coffee grounds before the full force of pressurized water is applied. The aim here is to prevent channels from forming in the coffee bed.

For our tests, we focused on finding out if there is an ideal pressure to set on your espresso machine, rather than exploring pre-infusion, lever machines, or other methods of varying pressure during the extraction process.

Now, let's dive into the tests our engineers conducted!

The effect of pressure on extraction

One of our key findings was that as pressure increased, extraction times also increased.

In other words, higher pressure resulted in slower pouring shots.

pump pressure chart

Logically, you would expect the opposite to be true. So, what is causing this phenomenon?

Our hypothesis was that the carbon dioxide gas produced by fresh coffee creates increasing resistance to the water as pressure rises.

To verify this theory, we conducted the same experiment using stale coffee. Stale coffee loses trapped gases over time, which is why it produces less crema and visually unappealing shots.

As expected, with the stale coffee, extractions followed the expected pattern. Higher pressure resulted in a faster flow rate. This suggests that the "gas theory" is likely responsible for the slower flow rate when using higher pressures.

pump pressure chart 2

This conclusion is further supported by examining the flow rate of water through the coffee bed using a flow telemetry device. The device tracks the pulses from the machine's flowmeter, providing a visual representation of the flow rate during each espresso shot.

Shots brewed at 12 bars quickly saturated the coffee bed but then experienced a slower flow rate compared to lower pressure shots. This suggests that the resistance is occurring early in the extraction process.

Another notable finding was that the strength of the espresso, as measured by Total Dissolved Solids (TDS), was more influenced by extraction time than pressure.

When extraction times were shorter, the TDS was lower. When extraction times were longer, the TDS was higher regardless of the pump pressure.

While pressure does have an impact, it's worth noting that when using fresh coffee, increasing pressure helped prolong the extraction time. This can be beneficial for lighter roast coffees that are harder to extract. On the other hand, lower pressures may be advantageous for darker roasted, more soluble coffees, as they help prevent over-extraction.

It's important to remember that the grind size also affects extraction times. Finer grinds will increase extraction times, but they also impact the balance and flavor profile of the coffee.

Now, let's move on to the most important question of all: which pressure produces the best-tasting espresso?

flair pump pressure dial

What Does 15 Bar Pump Mean?

Let's begin by looking at the other extreme. A 15-bar pump espresso machine exerts the maximum amount of pressure possible when brewing espresso.

Does this higher pressure result in better-tasting coffee? Not necessarily. Applying excessive pressure to the coffee grind can lead to over-extraction, resulting in a bitter or sour taste. Coffee beans are delicate and require a careful balance when brewing.

How Many Bars Are In a Professional Espresso Machine?

Professional, commercial-grade espresso machines typically use nine bars of pressure. These machines are usually pump-driven rather than steam-driven to achieve the desired pressure.

Different machines allow for varying levels of pressure, but it's advisable to leave this feature to experts to avoid unintended consequences.

Using a Cheaper 15 Bar Espresso Machine as a Home Barista Espresso Machine

It's possible to modify and use cheaper espresso machines for home barista purposes with some effort.

One example of a suitable machine for this purpose is the DeLonghi Dedica EC685.

Achieving good results with any espresso machine when starting out as a home barista can be challenging and involves a learning curve. It becomes even more challenging when dealing with the high pressure of 15 bar machines. However, it is doable.

The DeLonghi Dedica stands out for home barista use due to its:

  • Adjustable brew temperature.
  • Availability of bottomless portafilters.
  • Automatic pre-infusion.
  • Relatively temperature stable.
  • Superior milk texture compared to similar espresso machines.

For more information, please refer to:

Delonghi Dedica Coffee Machine Review

Best delonghi coffee machines review

Using pressured baskets versus standard baskets is another factor to consider.

Home Barista Espresso Machines

There are two categories of espresso machines: domestic espresso machines and home barista espresso machines.

Domestic espresso machines are designed to be more affordable and user-friendly compared to commercial-grade machines. They typically cost between £100-£200.

As mentioned before, they usually come with 15 bar pumps or higher without an overpressure valve, which means they extract shots at that pressure. They also use thermoblocks instead of brew boilers for on-demand water heating.

For more information on these types of machines, refer to:

Best Cheap Espresso Machines

Home barista machines, which are sometimes called prosumer machines, follow the same principles as commercial machines. They are more expensive and less user-friendly.

Home barista machines start around £400 and can go up in price. The popular La Marzocco Linea Mini, for example, costs almost four grand, although it's not the most expensive home barista machine available.

Used Espresso Machines - La Marzocco Linea Mini

For pricing details, please see:

Check Price - Coffee Hit

Check Price - Shop Coffee

The Sage Bambino Plus and the Gaggia Classic Pro are commonly chosen as the first home barista espresso machines, along with integrated grinder espresso machines.

Sage Bambino Plus Review

Gaggia Classic Pro Review

Pressurized Baskets vs. Standard Baskets

Standard espresso filter baskets have a single layer of metal with evenly spaced holes. Their purpose is to facilitate an even flow of extracted espresso while preventing coffee grounds from entering the cup.

Standard Filter Basket.

Pressurized baskets, also known as dual-walled baskets in the case of Sage/Breville, contain two layers of metal and only have a single tiny hole for the coffee to pass through. This design builds pressure, creating the appearance of crema.

Dual walled pressured filter basket.

So, pressurized baskets essentially simulate crema. However, the presence of crema doesn't guarantee excellent taste.

Best Budget Espresso Machines - Crema.

For more information on pressurized versus standard baskets:

Pressurized Baskets Vs. Standard Baskets

The beautiful crema that adorns our espresso shots is the result of precise extraction using high-quality freshly roasted and ground coffee beans. It's a byproduct of well-executed espresso brewing.

If you're interested in purchasing top-quality coffee beans, visit my site, The Coffeeworks. I offer fantastic blends of freshly roasted beans with clearly stated roast dates, unlike supermarket beans. Use the discount code CBNC25 to receive 25% off your first order and free delivery on two or more bags.

Click here to order from Coffeeworks with discount code CBNC25

With pressurized baskets, you can achieve visually pleasing crema without perfect extraction. However, to enjoy the perfect-tasting espresso, it's crucial to use high-quality beans, freshly roasted and ground, properly adjusted for extraction.

It's worth noting that in my tests, pressured baskets did yield slightly better results with the same coffee compared to standard baskets. However, the difference wasn't significant. This test was conducted using the Sage Bambino Plus, not one of the cheaper machines that boast 15 bars of pressure.

In this video, I experimented with both pre-ground coffee and freshly ground coffee using both pressurized and standard baskets.

For more information, please watch this video:

Pressure Baskets vs. Standard Baskets

The bottom line is that while pressured baskets can visually enhance crema, the taste may not live up to expectations. Exceptional taste can only be achieved through meticulous attention to high-quality beans, fresh grinding, proper extraction, and balance.

In conclusion, understanding the brew pressure of an espresso machine is essential for achieving the perfect extraction. The pressure plays a crucial role in extracting the flavors and aromas from the coffee grounds, and a 15 bar pump is considered the standard for achieving professional-quality espresso. However, it is important to note that the number of bars alone does not guarantee a great cup of coffee; factors such as the type of basket used and other machine features also come into play. Whether you opt for a more affordable 15 bar machine or invest in a professional-grade one, the key is to experiment and adjust the brew pressure to your personal taste preferences. With the right machine and technique, you can become the home barista brewing the crema of the crop.

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