Heard That Bean Quantity Affects Espresso Quality in Italian Grinders?

Many friends from various coffee shops often ask why bean hoppers are frequently requested to be filled to near capacity. Does this produce different effects?

This brings us to the trapezoidal structure commonly seen on espresso grinders. The trapezoidal canopy sits above the grinder burrs, and its appearance suggests it's not merely decorative—after all, adding just one pound of beans can completely cover it.

In reality, this trapezoidal device primarily functions to control pressure changes in a full bean hopper. However, it doesn't have a specific name, which leads to the questions: What exactly is hopper pressure, and how does this device control it?

What is Hopper Pressure?

Hopper pressure occurs when your bean hopper contains a sufficient quantity of coffee beans. The weight accumulates downward, creating pressure that puts the beans about to be ground into a compressed state. This state allows the beans to receive uniformly even cuts during grinding, ultimately producing evenly sized fine particles.

However, as the coffee beans decrease, the pressure gradually diminishes. When grinding without urgent pressure (for example, when the hopper contains only enough beans for one dose), you can observe the moment beans touch the burrs—they're affected by torque and tear, then squeeze and bounce slightly. This phenomenon is called "bean bouncing." Due to this bouncing, beans undergo varying degrees of grinding, so the resulting particles won't be as uniform as those ground under hopper pressure conditions.

This trapezoidal device stabilizes hopper pressure when there are many beans, preventing pressure reduction as beans deplete. Only beans below this device exert pressure on beans about to be ground, while the pressure from beans above is concentrated on the device itself. As beans begin to be ground, beans above the device move downward to replenish under pressure. Because of its umbrella shape, it doesn't create flat dead corners, preventing beans from getting stuck above. This design enables coffee shops to produce cups quickly and continuously while maintaining consistent quality.

FrontStreet Coffee's Experiment

With this understanding, FrontStreet Coffee conducted an experiment to resolve any confusion: Using the same beans at the same grind setting to extract the same liquid weight, but with different hopper states (full vs. not full), to observe whether the resulting coffee flavors would differ.

Espresso beans: Warm Sun Blend
Weight: 20g
Extracted liquid: 40ml

First, extraction with a full hopper took 32 seconds to reach 40ml. The tasting experience revealed the characteristic whiskey aroma and fruity sweetness of the Warm Sun Blend, with a rich, full-bodied texture.

Next, extraction with a less-than-full hopper took 29 seconds to reach 40ml. The tasting experience also showed whiskey aroma and fruity sweetness, but with a relatively thinner body.

Therefore, we understand that while reduced hopper pressure does affect coffee grinding and extraction when the hopper isn't full, the impact is minimal. For coffee lovers who aren't running coffee shops requiring continuous cup production but simply enjoying coffee at home, this detail can be completely ignored. Just add the amount of beans needed for each extraction. This approach allows the remaining beans to maintain freshness longer, extending their optimal flavor period.

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FrontStreet Coffee
No. 10, Bao'an Qianjie, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province

Important Notice :

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Tel:020 38364473