Grinding is one of the essential cornerstones for extracting excellent coffee, but it is too often underestimated if not ignored!
So: how should the coffee be ground?
The answer is only one: there is no one answer!
Yes, because the grind is not unique to all extraction methods; it also varies as environmental conditions change.
The importance of grinding
Before we begin we need to understand why grinding is important:
- It affects the extraction and color of the drink;
- It affects the taste and aroma in the cup;
We also grind because:
- Flavor substances, created during roasting, are trapped in the cells of the coffee bean. By grinding we segment the grain into very small parts. In this way the water, during extraction, has a chance to hit many more cells, breaking the “barriers” and thus releasing the aromatic substances;
- To increase the extraction area. In fact, by grinding we have already said that we segment the grain into thousands of smaller particles. This allows the water to “touch” a greater surface area of the grain and thus extract more substances.
Different grindings for different extraction methods
Now that we understand the importance of grinding, we need to understand how to grind coffee!
Each tool used for coffee extraction has its own specific level of particle size, that is, the thickness of the coffee powder obtained.
The degree of grain size depends:
- From the temperature of the water used for extraction;
- From the pressure exerted on the mince loaf;
- From the type of extraction, namely: percolation, pressure or infusion.
Let’s immediately make a practical and concrete list to understand the right grind for each extraction tool used:
- For Cold Brew and French Press, a wide ground coffee, similar to coarse salt, will be used. If we want to be precise, the particle size of the mince should be between 800 and 1000 microns;
- For Chemex, V60, and Clever, a medium to coarse grind, similar to fine salt, will be used. The particle size should be between 500 and 700 microns;
- For Moka, Syphon, and Aeropress, on the other hand, a medium grind, similar to fine sugar, will be used. Particle size will need to be within the 400-600 micron range.
- A fine grind, similar to powdered sugar, between 200 and 300 microns will be used for Espresso.
- Finally, for the Turkish you will need very fine ground coffee, under 200 microns.
PS. 1 micron is equivalent to 0.001 millimeter. There are special tools to check grain size, but more simply a visual check is made.
We must now learn to assess by eye whether that specific grind we have on hand is correct or should be varied.
Small clarification: the grind is not fixed!
Let me explain: the coffee that we ground yesterday and was perfect is not necessarily still good today. It is true, however, that for most methods very small variations in grain size do not result in a striking deterioration in extraction.
However, this rule should be kept in mind for the Express. In fact, the only way to extract great espresso is to have a perfect grind for that moment.
Visual inspection of grinding correctness
The basic concept:
- If the coffee is ground too wide, the drink will go down faster;
- If the coffee is ground too fine, extraction will be slower, or even not happen at all.
If the powder is too fine, it will be very compact and there will be less room for water to pass between grains. The latter will then find too much resistance and remain in contact with the coffee for a long time. Given the high temperatures of the liquid, around 95°C, the coffee will burn.
The coffee will be over-extracted, thus bitter and with an empyreumatic, i.e., burnt, taste.
On the contrary:
If the powder is too large, there will be much more room for water to pass between the ground grains. The latter will find no resistance and will complete the extraction very quickly.
The coffee will be under-extracted, thus watered down, not very aromatic, more acidic and astringent.
So: if the water goes through too fast we have to tighten the grind; conversely, if we see that the water does not go down, we will widen it.
Let’s delve into the methods of coffee extraction
The espresso machine operates under pressure, so the water must find a strong hydraulic resistance given by the ground coffee cake. This is why a very fine grind is used and the grind itself is well pressed before extraction.
It is said that the extraction is perfect if the coffee goes down in a rattail pattern, that is, a linear line that is wider above and finer below.
In almost all filter coffees with manual extraction, no pressure other than atmospheric pressure is impressed, except for Aeropress.
They are distinguished into infusion and percolation:
- French Press and Clever are infusion, in that the coffee remains in contact with the water for the entire extraction time, or nearly so, just as it does with tea. This is why a wider grind is required, as no resistance is needed. In addition, the extraction time is long, so the wider grind is useful to get the water into the grind grain slowly, otherwise there would be a risk of over-extracting it;
- V60 and Chemex, on the other hand, are percolation methods, in that water passes through the grind and the beverage is then collected in a container below. Here the grind must impose a minimum of hydraulic resistance on the water, which would otherwise run off too quickly, making the drink under-extracted and lacking in flavor. In this case, extraction times are between 2 and 3 minutes: if the beverage is ready in less than 2 minutes, it means that a finer grind will be needed; conversely, if it takes more than 3 minutes, a wider grind will be needed.
With this method, the pressure is that of steam, which, upon reaching 100°C, pushes water through the coffee cake to settle in the upper reservoir.
The mince must impart a minimum of resistance, again so that the water does not pass through too quickly and thus make the drink under-extracted.
At this point, all you have to do is choose the coffee best suited to you and purchase it ground for your desired extraction method.
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