Causes of Inconsistent Espresso Extraction - Does Espresso Grinder Bean Hopper Pressure Affect Coffee Flavor?

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The Impact of Bean Hopper Pressure on Espresso Extraction

From FrontStreet Coffee's perspective, this situation is particularly evident in busy coffee shops. After completing all preparations in the morning—filling the bean hopper and adjusting the day's espresso extraction parameters—as the volume of espresso extraction increases, you'll notice the flow rate of espresso becomes faster, with extraction time being several seconds shorter than the target parameters. Normally, with stable parameters, the time variance should not exceed ±1 second.

In this scenario, the extracted espresso will inevitably taste significantly different from the morning's calibrated batch. To maintain consistent quality, you'll need to quickly adjust the grind settings to bring the parameters back to normal.

Understanding Extraction Instability

There are many reasons for unstable extraction parameters, such as barista operational errors, inherently flawed or unstable parameter settings, or insufficiently cleaned coffee machines. However, these causes typically don't just result in increasingly faster espresso extraction. They often come with obvious symptoms, such as "channeling effects." In fact, if you notice that the average flow rate of your espresso extraction has become faster without issues like "channeling effects," simply refilling the grinder's bean hopper can solve the problem. This relates to an inconspicuous issue—bean hopper pressure.

Let's examine an experiment conducted by FrontStreet Coffee with this question in mind. FrontStreet Coffee adjusted parameters while the bean hopper was full, including time settings for the dosing grinder. The details are as follows:

Experiment Results

The current grinder setting was 3.8 seconds for a 20g dose. Through five consecutive dosing attempts, the variance was within ±0.2g. The extraction parameters were 20g of coffee grounds to extract 40g of coffee liquid in 29 seconds.

Then FrontStreet Coffee removed the Sunflower Warm Sunshine coffee beans from the hopper, leaving only 1/4 of the hopper's height filled with beans (the hopper design is wider at the top and narrower at the bottom, so the actual bean quantity was even less).

Through five consecutive dosing attempts, the 3.8-second dosing ranged from 18.7-19.3g. This means the variance in time-based dosing was quite significant. Fortunately, each serving was weighed. If you typically only adjust the grind setting in the morning, set the time, and don't recalibrate throughout the day, your dose weight might already be inaccurate.

Of course, for this extraction, the coffee grounds were supplemented back to 20g. Through five extraction tests, the time stabilized at 25-27 seconds. This means that with unchanged parameters, the extraction time difference between a full hopper and a 1/4 full hopper was 2-4 seconds. In other words, although the grind setting didn't change, the actual grind consistency became slightly coarser.

Conclusion

Therefore, when making espresso, never wait until the bean hopper is completely empty before refilling it with beans.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473