MHW-3BOMBER - Dec 2 2024
What is the Channeling Effect? Why Does It Occur? How Can It Be Avoided?
When making espresso, even if all parameters are seemingly correct, the resulting coffee may taste strange—sharp, acidic, and weak. Upon inspection of the coffee puck, you might find a hole in the center. Many coffee enthusiasts wonder why this hole appears in the puck and how it relates to the taste of the espresso.
Channeling Effect
The hole in the coffee puck is caused by the "
Causes of the Channeling Effect
1. Coffee Beans
Yes, the beans themselves can affect the extraction process, especially if they are very fresh. Espresso beans are typically roasted to a medium-dark level. Freshly roasted beans release significant amounts of carbon dioxide when they come into contact with water. Unlike pour-over coffee, which allows for gas release, the trapped gases in espresso brewing prevent water from fully saturating the grounds. This forces water to flow around the edges, creating channels.
2. Uneven Coffee Grounds Distribution
While dosing and distributing coffee grounds may seem trivial, poor distribution leads to uneven density across the coffee puck. Variations in puck thickness cause inconsistent water flow during extraction, often resulting in puck perforation and channeling.
3. Uneven Grind Size
Mixing coffee grounds of varying sizes can lead to problems. Fine particles may clump together, blocking water flow, while larger particles create paths of least resistance, forming channels.
4. Uneven Tamping Pressure
Inconsistent tamping pressure results in an uneven density in the puck. Water naturally flows through areas with less resistance, causing channeling.
5. Unstable Water Pressure or Extraction
Variations in machine water pressure or temperature can concentrate water flow in specific areas, further exacerbating channeling.
How to Avoid Channeling Effect？
1. Reduce Degassing
Allow freshly roasted coffee beans to rest (age) to stabilize the degassing process. A resting period of about 10 days is recommended for espresso beans. This allows the gases to dissipate and ensures a more stable extraction process.
2. Proper Dosing
When dosing manually, rotate the portafilter evenly while dispensing coffee to ensure even distribution. Alternatively, using a blind shaker can help achieve better distribution. For the blind shaker, activate the lever to ensure the coffee grounds fall evenly across the basket.
3. Uniform Grounds
Distribution
Before tamping, ensure the coffee grounds are evenly spread throughout the basket. Both the surface and interior, including the edges, should be uniform without voids. Use tools like distribution needles and tampers for this purpose.
Needles Distributors : These break up clumps in the coffee grounds, dispersing them evenly and eliminating voids. By gently stirring or swirling the grounds, you can ensure an even distribution and prevent channeling during extraction.
Distributors: These tools help flatten and level the coffee grounds’ surface, creating a consistent density throughout the puck. Position the distributor on the basket and rotate or press lightly to achieve a level and compact puck surface.
4. Tamping
Tamping applies pressure to compact loose coffee grounds, enabling pressurized water to pass through evenly. Apply consistent and perpendicular downward pressure when tamping. Ensure that your tamper matches the size of your basket; a mismatched tamper may leave edges uncompressed, leading to channeling during extraction.
Conclusion
In summary, apart from factors related to the coffee beans themselves, channeling is primarily caused by uneven dosing, distribution, and tamping. Paying attention to these steps during espresso preparation can significantly reduce the occurrence of channeling and improve the quality of your espresso.
