Impact of the grind size on the final flavor of coffee

If you want a quality cup of coffee with exceptional flavor, it is important to understand how inadequate grinding affects the coffee’s flavor, aroma, and texture.

In addition, we must consider other external factors, such as the grind’s size, which also significantly impact the coffee that is extracted. In this article, I will explain in detail the importance of these factors.

How does grinding affect the coffee extracted?

Coffee grinding is a fundamental aspect that directly affects the quality of the prepared cup. The reason is that this process allows the flavors and aromas of the coffee to be extracted more easily during the preparation.

The size of the grind influences the speed of coffee extraction:

• Finer grind: increases the surface of contact of the water with the coffee, increasing the extraction speed. As for the coffee, it will be bitter, acidic, or even unpleasantly strong.
• Coarser grind: reduces the contact surface and decreases the speed of extraction. As for the coffee, it will be weak, tasteless, and unsatisfactory.

The grinding is a key factor in the preparation of coffee and should be carefully adjusted to obtain the best flavor and aroma of the coffee extracted.

The aromatic substances generated during the roasting process are encapsulated within the cells of the coffee bean, and only when they are broken can they be released to be perceived in the final beverage. In the image above, you can observe this:

1. The first image shows a fine grind; each square represents a small ground coffee bean.
2. The second image shows a medium grind.
3. The third image shows a coarse grind.

Now let’s observe how the water (the blue color in each image) passes through the coffee beans for 120 seconds in each scenario:

• In the first image, there would be an over-extraction due to the constant contact of the coffee beans with the hot water. Each particle would be penetrated with greater intensity, resulting in the burning of its exterior.
• In the second image, optimal extraction would be achieved due to the medium size of the ground coffee beans. The water would have adequate time to penetrate the interior of each particle slowly, extracting all the soluble solids at the precise moment.
• In the third image, under-extraction would occur because the water would not reach the center of the particle in 120 seconds, as it would be too deep in relation to the bean surface.

Grinding size according to the type of extraction

For this, it will be taken into account that one micron is equivalent to one-thousandth of a millimeter:

• French Press and Cold Brew require a very coarse grind size, i.e., between 800 and 1000 microns.
• Filter coffee machines and other percolation methods require a medium coarse grind size, between 500 and 700 microns.
• Moka pot makers require a medium-fine grind, around 400 to 600 microns.
• The adequate grind for espresso should be between 200 and 300 microns.
• The grind for the Turkish coffee maker should be extra fine, below 200 microns.

Note: without the proper instruments, measuring the grind size in microns is impossible. These references are a starting point for each type of extraction.

External factors that affect the coffee grinding process

We must keep in mind that ground coffee is much more sensitive than the whole bean and some external factors can affect it:

• Humidity: Coffee beans absorb humidity and become more difficult to grind.
• Temperature: If the environment is too hot, it can cause the oils from the coffee to adhere to the grinder’s blades and affect the grind’s quality.
• Altitude: At higher altitudes, the air is less dense and can affect the consistency of the grind.
• Air: after grinding, the aromas and flavors of coffee begin to be lost due to oxidation produced by exposure to the exterior.
• Coffee quality: coffee beans of different varieties and origins can have different densities and hardnesses, which can affect the consistency of the grind.
• Storage: inadequate storage after grinding can accelerate the loss of aroma and flavor. Therefore, storing ground coffee in an airtight container and using it as soon as possible to maintain its freshness and flavor is important.

Note: I recommend that you buy coffee beans and grind them just before using them to obtain better quality in terms of flavor. If this is not possible, it is important to pay attention to the type of packaging of the coffee you buy.

Types of coffee containers

The types of coffee packaging should be considered:

1. Opaque containers help the ground coffee not to come into contact with light.
2. Vacuum-sealed, they help to prevent the coffee from oxidizing due to contact with air and/or humidity.
3. Containers with one-way valves allow the coffee to continue degassing without letting gases escape, especially carbon dioxide, which continues to be produced naturally.

In this way, the freshness and flavor quality of the coffee can be maintained for a longer period of time. Avoid transparent and zip-lock containers since they do not offer good protection against oxidation and humidity.