Using a burr grinder will significantly improve the quality of your coffee as it will always produce a more even grind. With burrs, the beans are ground under pressure, they work by forcing the coffee beans through a set of burrs. One burr remains stationary while the other rotates. When the coffee beans are forced through the burrs, they are crushed to the desired consistency.
What is the difference between burrs?
They are different in several aspects: noise, particle distribution, cost, heat and grind retention.
Flat burrs are made up of two rings that lie flat on top of each other. They are usually aligned horizontally and have angled teeth. One of the burrs rotates while the other remains stationary. The coffee passes through the center of the burr and exits the burr horizontally along the edge of the burr. Without the assistance of gravity to feed the grains through the burrs, a flat burr grinder needs to use only centrifugal force. This means that a flat grinder needs to spin much faster and therefore has much higher RPM (around 700 RPM) and a more powerful motor. The distance between the rings determines the grind size.
Conical burr grinders have a more vertical configuration and are ground directly above the outlet. One burr is inside the other. The outer burr is a hollow circular ring with angled teeth and the inner burr is conical with a larger base that also has small teeth. The outer burr remains stationary while the inner burr rotates. There is a wider opening at the top through which the grains pass. They are then crushed into smaller and smaller pieces until they descend vertically through the opening at the bottom of the burrs. The distance between the two burrs is what determines the grind size. With the conical burr, the grains pass through the burrs vertically with the help of gravity.
The biggest difference between them is that in conical burrs it is necessary to achieve perfect parallelism and perfect concentricity, while in flat burrs only parallelism is necessary, which results in greater particle size homogeneity.
The more perfect the parallelism, the greater the granulometry precision.
A conical burr creates what is known as a bimodal particle size distribution. This means that it produces two different grind sizes: fine (tiny particles) and larger ones, due to the difficulty in creating a perfect alignment between the parts.
The fines restrict the flow of water through the coffee bed, allowing time for the larger particles to be extracted. This slower flow creates your conventional espresso with a thick, rich body and hints of bitterness. The extraction is uneven and preparing the espresso is a great balancing act, allowing time for the larger grinds to be extracted to that ideal point, without allowing the fines to extract too much.
In contrast, a flat burr grinder produces a unimodal particle size, with a single grind size. The uniform grind size gives you the flexibility to play more with espresso shots. You can get longer pours with higher extraction rates without having to worry about fines during extraction and producing bitter flavors. The lack of flow restriction (by the absence of fines) means you will have to grind finer or extract longer shots to get the same level of extraction.
Flat burrs spin faster, creating more friction than tapered burrs, and use a larger motor to achieve the required speed. Both factors create additional heat in the grinder, but flat burrs, because they use greater engine power, have greater heat retention. Heat can damage the delicate oils and aromas of the coffee bean, changing the flavor profile, and the extraction speed of the espresso can change when the grinder heats up, requiring you to change the grind size.
Flat burrs have greater grain retention potential during grinding. Trapping occurs when ground coffee sticks to the surfaces of the grinder. This is more likely to happen with flat burrs than conical burrs due to the way the coffee comes out of the machine.
With flat burrs, the coffee is pushed sideways out of the burr assembly. This requires a lot of force, and to achieve this, the grinding machine's motor rotates at a higher speed. Conical configurations, on the other hand, require less mechanical force as gravity helps feed the grains. This means the risk of retention is lower.
This retention can alter the extraction of espresso coffee, as the old coffee that remains stuck to the burr can mix with the fresh coffee, causing contamination of the soil.
Generally speaking, flat burrs are more consistent and more expensive. Depending on the model, they can also be noisy and heat up quickly, which may require more adjustments throughout the day as the temperature rises, unless they have a good ventilation system. This is due to the higher RPM.
Conical burrs are quieter, cooler and cheaper, but less consistent.
Understanding the positive and negative points of both systems is important to form an opinion and decide which one is best for your objective.
But it's worth considering that if you're a home barista, a conical burr grinder will probably be sufficient for your needs. They are more affordable, run quieter and cooler, and are easier to use.
However, if you are in a commercial setting or want to start making more technical espresso, a flat burr will be more suitable. They arguably produce a more consistent grind and will give you more flexibility to play around with different extraction parameters.
What type of grinder would you have at home, flat or conical burr?
Comentarios