How to Grind Coffee Beans into Coffee Powder - Espresso Grinding Coarseness Adjustment

Understanding the Impact of Burr Temperature on Coffee Grinding

For coffee professionals, the most challenging daily task is adjusting espresso grinding. As coffee beans change their state day by day, even at the same grind setting, the particle size, extraction time, and flavor will vary. This often requires tasting several espresso shots before determining appropriate extraction parameters.

While the daily state of coffee beans certainly affects grind size, other external factors also influence coffee grinding! For instance, the cleaning of grinder burrs and residual grounds in the hopper/chute, the amount of beans in the hopper, environmental humidity, and the temperature of grinder burrs—these frequently overlooked details all change coffee particle size and flavor. If you don't check these details and randomly adjust parameters, you'll waste so many coffee beans!

Cleaning Grinder Burrs and Residual Grounds in Hopper/Chute

We believe that coffee professionals clean their coffee grinders daily, but usually just the surface, rarely thinking about removing the burrs to check for ground clumps. While burrs don't need frequent cleaning, they shouldn't be completely neglected. Whether it's an espresso grinder or single-origin grinder, it's necessary to remove the burrs for thorough cleaning every week! But don't wash them with water~

Espresso beans typically use medium-dark or darker roasts. As these roasted beans continuously release carbon dioxide, they develop an oily surface. Each time they're ground, some of this oil adheres to the burr teeth. Over time, coffee grounds stick together forming clumps. When these clumps fill the space between burr teeth, they cause uneven particle size, ultimately affecting extraction quality.

Meanwhile, residual grounds in the chute/hopper lose their flavor as they're exposed to air for longer periods. When freshly ground coffee mixes with these old grounds during extraction, the resulting coffee exhibits unpleasant flavors like bitterness and woodiness. Therefore, when the grinder hasn't been used for more than 15 minutes, you need to use tools to clear the grounds from the chute/hopper before grinding again.

Temperature of Grinder Burrs

When a grinder operates at high speeds for extended periods, the burrs gradually heat up. This heat affects two aspects. First, when burrs are hot during grinding, particles become coarser and more uneven. Some research reports indicate: with the same grinder at the same setting, beans ground with room temperature burrs produce finer and more uniform particles. Hot burrs increase the toughness of bean structure, resulting in coarser or uneven particles.

Second, burr heat accelerates the evaporation of flavor compounds in coffee particles, while also increasing temperature throughout extraction, thereby reducing coffee viscosity. Don't think that differences of just a few degrees don't matter—these subtle variations can cause dramatic changes in overall coffee performance.

Environmental Humidity

Moisture in the air affects both coffee bean storage and grinding at varying levels. Whether due to climate changes or turning off air conditioning/heating at night, environmental humidity fluctuates. For coffee beans that require cool, dry storage, you should keep the hopper lid closed during daily operations, and transfer beans to dry containers or original packaging for sealed storage at night.

When coffee beans or grinder burrs become damp, coffee easily forms clumps during fine grinding. If these clumps aren't properly broken up during extraction, they result in "clustered" extraction—where water continuously washes over outer particles causing over-extraction, while inner particles aren't effectively extracted. Additionally, clumps affect water flow channels through the coffee bed, ultimately leading to uneven extraction.

Amount of Beans in the Hopper

This is the most easily overlooked detail! Many coffee professionals only refill the hopper when it's nearly empty. Don't do that! Whether the hopper is too full or too empty will change coffee grind size.

When the hopper is full, beans are compressed during grinding, producing finer particles. Conversely, when there are too few beans in the hopper, coffee beans have enough space to "bounce" during grinding, resulting in coarser or uneven particles. FrontStreet Coffee suggests maintaining the espresso bean hopper at approximately 2/3 full, never dropping below 1/3.

For professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style).

For more specialty coffee beans, please add FrontStreet Coffee on WeChat (ID: kaixinguoguo0925).

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473