Coffee Extraction Basics: What Are the Detailed Requirements for Making Espresso?

Espresso, the "soul" of the Italian coffee system, can be extracted in just 20-30 seconds. However, before pressing the brew button to start extraction, if certain operational details are not properly handled, it could result in a poorly tasting coffee.

Today, FrontStreet Coffee will share with you 7 small details you might not have noticed when making espresso.

1. Forgetting to dry the portafilter before adding coffee grounds

After extraction is complete and the used puck is discarded, rinsing the portafilter with water to remove residual coffee stains (and grounds) and drying it before the next extraction should be a default action for all baristas.

However, some friends are quite impatient and add coffee grounds without wiping the portafilter dry. The coffee powder that first contacts the wet portafilter will become prematurely moistened and clump together. Subsequent distribution and tamping have minimal impact on these "clumps." Therefore, when extraction occurs under these circumstances, it's understandable why the espresso flow rate fluctuates between fast and slow, and the resulting espresso taste becomes very inconsistent.

2. Severe clumping of ground coffee

Because the coffee powder used for espresso is "as fine as flour," it tends to clump during the grinding process. Additionally, some extremely dry weather conditions can cause原本 non-existent clumps to become very noticeable.

Although nothing appears wrong after tamping, these clumped powders have a tighter structure that makes it difficult for hot water to penetrate, causing it to find alternative paths with less resistance to escape. This eventually creates channeling, and in severe cases, is accompanied by jet streams of liquid, affecting the coffee's flavor. When you discover that your ground coffee has very noticeable clumps, you might want to use a distribution needle or thin needle-like objects to gently break up these clumps.

3. Tamping directly without proper coffee distribution

Simply put, distribution ensures the coffee grounds are evenly and smoothly distributed in the portafilter, allowing hot water to "fairly" penetrate every coffee particle, keeping their extraction state as consistent as possible.

However, some friends add (dose) the coffee and immediately begin tamping without "leveling" the coffee bed. From the surface, the coffee puck might have slightly inconspicuous depressions. During actual extraction, hot water under 9bar pressure will concentrate on these "small pits," leading to perforation and jet streams of liquid. Additionally, if there's water residue on the tamper, it will also take away some coffee powder, making the puck surface uneven. Therefore, FrontStreet Coffee suggests trying to make the fluffy coffee grounds as level as possible before tamping, or using a distribution tool (dosing tool) to assist with distribution.

4. Uneven pressure during tamping

Besides uneven distribution, improper tamping technique will also affect the final espresso flavor. Some coffee enthusiasts new to making espresso are not yet skilled in the tamping motion and will repeatedly press back and forth. Although the coffee bed looks very level in the end, the actual density distribution of internal coffee particles has been completely altered, making extraction more prone to channeling.

Therefore, when using the tamper, try to complete the motion in one smooth motion. If this is truly difficult to accomplish, FrontStreet Coffee suggests reviewing the tamping technique again.

5. Accidental bumps when attaching the portafilter

FrontStreet Coffee has encountered situations where new colleagues, not yet familiar with the coffee machine in the shop, would fumble and bump against the brewing head before finding the correct angle to attach the portafilter. This might cause the originally tightly compressed puck against the portafilter to separate and "crack," greatly increasing the probability of "punctures" and channeling. This situation is not only very common in home brewing but is also frequently seen among new baristas with more exaggerated movements. (P.S. FrontStreet Coffee gives such new colleagues some adaptation time before participating in daily production.)

6. Not flushing the group head

Each time you remove the portafilter to discard the puck while simultaneously pressing the brew button to release water—this might be a subconscious action for baristas at the counter. This is because after extraction is complete, some coffee grounds and stains inevitably remain on the shower screen. If not flushed away promptly with water, by the time of the next extraction, they would have been dried and stuck to the surface, eventually being extracted together, and the resulting espresso flavor is predictable.

Another situation is when there's a long interval between this extraction and the previous one, causing the shower screen on the group head to become too hot. Directly attaching the portafilter might cause the surface coffee grounds to be scorched, potentially leading to a burnt bitter taste in the espresso.

Therefore, to avoid negative flavors in coffee caused by the above situations, FrontStreet Coffee recommends everyone develop the habit of flushing some water before and after extraction.

7. Delaying the brew button after attaching the portafilter

Some friends, after tamping and attaching the portafilter, realize they haven't prepared their electronic scale yet, then frantically busy themselves with preparation. By the time they press the extraction button, the extracted coffee will likely have a burnt bitter taste. (FrontStreet Coffee often waits about ten seconds while taking photos due to focusing, and the final espresso ends up with a slight burnt flavor.)

Because the group head temperature is very high, if extraction doesn't start promptly after attaching the portafilter, the puck will be baked by the high temperature and develop a burnt taste. Therefore, remember to complete all preparations (electronic scale, shot glasses, etc.) before attaching the portafilter, and start extraction immediately once it's securely locked to avoid over-extraction and waste.

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FrontStreet Coffee
10 Bao'an Qianjie, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province

Important Notice :

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Tel:020 38364473