Although making espresso may be a speedy process, it is not an easy one. When you draw a shot from a coffee puck, a lot of different things are happening inside of it, both chemically and physically. To make matters even more complicated, the way in which the water interacts with the dry grounds at the beginning of the extraction process will be significantly different from the way in which it behaves only five seconds later, and this will have an effect on the taste of the espresso.
I had a conversation with Lauro Fioretti, the Chief Engineer of the Simonelli Group, an Italian company that manufactures espresso machines and grinders. The Simonelli Group is comprised of Nuova Simonelli and Victoria Arduino. Continue reading to learn about the three parts of the espresso extraction process as well as what you can do with the information you gain.
Lee este artículo en español Presión, Pulsación y Las 3 Fases de la Extracción del Espresso
Espresso shots. Credit: Fernando Pocasangre
During the pre-infusion step, the water will first come into touch with the coffee grounds. At this stage, the goal is not to remove it; rather, it is to prepare the puck for use.
Lauro informs me, “When making filter coffee, the standard procedure is to pour some water over the coffee bed from the very beginning.” As the water reacts with the coffee, the CO2 trapped within the grounds is released as air bubbles. This marks the beginning of the blooming process.
These air bubbles create a disturbance in the coffee bed and also prevent part of the grounds from receiving water. After then, they vanish, and the coffee bed goes back to its original state. Therefore, allowing the bloom to take place before beginning the extraction process allows a more level and constant soaking of the coffee grounds.
Espresso adheres to the same guiding idea. Because of this, it is essential to let espresso beans degas before using them in a brewing process. This results in the production of less carbon dioxide throughout the brewing process.
It is also essential to keep in mind that various manufacturers of espresso machines use different pre-infusion techniques. According to Lauro, the pre-infusion process at Simonelli Group is broken up into two distinct stages: the pre-wetting stage, and the pre-infusion stage. According to what he has said, “Pre-wetting is normally a feature that we trigger when we drink a really fresh coffee.” By activating the solenoid valve, it makes it possible for the machine to let out the carbon dioxide that is trapped within the coffee puck.
He goes on to say that, “If your coffee has already been degassed adequately, then there is no need to remove the extra CO2.”
Concerning the pre-infusion process, he informs me that the puck “will get moist, will absorb the water, will emit CO2, and will grow.”
During the pre-infusion and pre-wetting processes, he emphasises how crucial it is to have a coffee bed that is stable. “[to employ] the appropriate amount of time,” he continues, “is of the utmost importance.” If you do this too rapidly, the CO2 will still be being emitted even after the infusion has started.
The force with which the water strikes the puck causes a disruption in the coffee grounds, which is another factor to take into consideration. Espresso owes its potency and quick extraction time to pressure, with many machines extracting at 9 bars, which is the industry standard. However, this may cause grounds to be displaced.
According to Lauro, “it is vitally crucial to prevent, as much as possible, any possibility of channelling,” and “channelling” During the pre-infusion phase, if the water hits the coffee at a full 9 bars of pressure, it may upset the puck and cause specific places to become easier for the water to channel through. This, in turn, might result in extraction that is not uniform.
During the pre-infusion process, Lauro emphasises how important it is to remove all forms of mechanical pressure so that the hot water may flow freely. It is intended to moisten the puck in a uniform manner.
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Adjusting the various parameters on the Aurelia Wave. Credit: Miguel Regalado
Infusion is the next step in the process. Lauro informs me that the optimal time for this to take place is when the whole coffee puck has already been soaked, as this would “create a stable structure with a constant resistance to the flow of the water.” This results in the coffee puck “having the highest resistance to the water,” as he explains it, after the pre-infusion step has been completed.
As he goes on to explain, the pressure may be raised to the highest degree that is required (which is generally around nine bars). He continues by saying that “during the infusion phase, you can observe that the flow rate is growing.” This is as a result of the fluctuating resistance that occurs as the puck grows wetter.
According to Lauro, this is also the time when the vast majority of chemical reactions take place. Everything from the coffee, including its fragrance, acidity, sweetness, and bitterness, is being removed.
The flavour of the espresso may be altered by adjusting the amount of time spent in the infusion process. Typically, the fruity acids are the first thing that are extracted, followed by the sweetness and the body, and then bitterness comes last. In general, an espresso that is well-balanced will include components of each of these qualities. Nevertheless, the appropriate extraction time for a particular coffee will vary according to factors such as the country of origin, the kind of processing done, the roast profile, and more.
In particular, it is important to keep in mind that darker roasts will be more soluble than lighter roasts since the structure of the coffee will have been destroyed. It takes longer to generate the same profile with a lighter roast as it does with a deeper roast.
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Taking a shot of espresso from the machine. Credit should go to Fernando Pocasangre
Post-infusion refers to the last few seconds of the espresso shot pulling process. According to Lauro, “The majority of the desired compounds are already in the cup, and we start to [extract] some other compounds that are less favourable, but we need additional liquid in the cup to balance the components.” It’s possible that the shot will be overly powerful if you don’t have this.
A ristretto. The author is Neil Soque.
Different Phases, Different Flow Rates
According to what Lauro has told me, in the conventional method, “during the extraction phase, the coffee cake is forced by high pressure for the whole duration.” Therefore, all of the coffee grounds are packed together and pushed up against one another for such a long period of time.
Working with International Hub for Coffee Research and Innovation and the University of Camerino, Lauro explored ways to “create waves [of water] that can relax the coffee bed to give the possibility to the water to penetrate more, so as to increase the permeability into the coffee grounds.”
This laid the groundwork for the development of the Pulse Jet technology by the Simonelli Group, which is included in the Aurelia Wave espresso machine. Different flow rates that are pulsed through the puck may be selected by baristas for each of the three steps that make up the espresso extraction process.
Lauro emphasises that “We cannot argue that one profile is better than another since, of course, it is extremely personal and depends on what you are searching for.” He used the example of two types of coffee that the team tested, a thoroughly washed Ugandan and a natural processed Peruvian, to illustrate his point. Before the coffees were assessed in a blind tasting by six Q graders, each coffee was extracted using the standard method as well as three distinct profiles, each of which had changing flow rate levels throughout the various stages.
According to him, “using the Pulse Jet, we saw that the acidity was arriving much more mildly. This was the case with the washed coffee.” We were successful in lowering the level of acidity while simultaneously improving the coffee’s overall flavour profile. Therefore, the sweetness and the acidity came together to create a taste that was well-balanced.
His next statement is as follows: “In the natural coffee,” he says, “we had a fantastic body, with all of the extraction methods, that what you anticipate from a natural coffee, tremendous sweetness.”
“So what we advise,” Lauro explains to me, “is that you put your coffee in, you dial in your coffee – so you select your brew ratio, and you choose your temperature – and then you start to play with the Pulse Jet, and you taste the coffee… You may essentially build a new flavour profile for your coffee, as well as a new equilibrium, with the help of [it].
The effects of running a few different Pulse Jet programmes on the flavour profile of two distinct coffees. Data source: Simonelli Group. The artwork is by Carlos Santana.
Every step of the espresso extraction process is unique, from the pre-wetting to the post-extraction, and awareness of this has the ability to assist baristas in providing superior coffee service. Understanding that coffee needs to degas, that different flow rates and pressure profiles may suit different coffees, and the importance of a well-balanced extraction can all contribute to more delicious espresso shots and more satisfied customers.
The featured image shows a barista pulling a double shot of espresso.
Please take into consideration that the Simonelli Group has provided support for this article.