Grinding has always been a much discussed topic, sometimes simple in application, but complex in its understanding.
Finding the correct grind is a mechanical act, which requires a few precautions and clear and simple references.
But understanding the importance of finding the perfect grind is not always so intuitive.
So here is a guide on the correct grinding of coffee, with Caffè Ernani!
Start your journey with this video:
What is grinding?
The term Grinding describes the operation of breaking coffee beans into multiple smaller sections.
Based on the size of the ground coffee and its uniformity, we are able to define the different levels of resistance of the coffee to the passage of water.
In other words: the degree of grinding modifies the extraction speed.
To understand this, just give a very simple example:
Imagine you have two buckets, one full of rocks and the other full of fine sand.
Now pour a basin of water over it.
In the first bucket, the one with the stones, the water will pass very quickly, reaching the bottom quickly, because between one stone and another there is a lot of space to pass through. On the contrary, in the bucket with sand, the water will pass much more slowly, as the passage space is very small.
The same concept is applied to coffee: if we grind it very large, the water will pass quickly, while if we grind it very fine, the water will have a lot of difficulty passing through it.
Why is coffee ground?
This is a complementary answer to the previous one:
We grind because we increase the contact surface between the water and the coffee during the extraction phase, thus helping to transfer the soluble solids from the ground coffee to the final drink in the cup.
Let’s understand better: if we had a whole grain, as in the image on the left, the water, represented by the blue line, would only pass over the surface, thus bringing only the oils deposited on it into the cup.
The final drink would therefore be very dull, without body or aroma and above all of a very dull light yellow.
While when we break the bean into small pieces the water manages to pass through it, investing it completely and therefore managing to bring not only the oils into the cup, but all those substances that allow us to savor and enjoy an excellent extracted coffee, such as lipids, carbohydrates, nitrogen compounds, etc.!
P.S. The size of the ground particles is defined as grain size and their size is calculated in microns (µ): 1µ = 1000mm, on the contrary 1mm = 0.001µ.
So why is grinding important?
Because it influences over or under extraction and the color of the final extracted drinkdThe consequence influences the taste and aroma of the final drink.
We have already addressed this topic in the past. I’ll show you both the video and the complete article.
Also read the related more in-depth article on the importance of grinding:
Getting back to us, let’s try to understand how it is possible that grinding influences the taste of the drink so much.
Graphic of a coffee bean with the different possible extraction percentages indicated The bean is composed of 30% soluble substances, i.e. substances that dissolve when water passes and therefore manage to reach the cup, and 70% non-soluble substances, i.e. which do not dissolve and therefore do not reach the cup.
But that 30% of soluble substances does not have to be completely extracted, it is in fact better to extract around 18-22% of substances to have a balanced drink with a tasty aromatic profile.
In other words yet:
- if I extract less than 18% I will have a drink in the cup defined as under-extracted;
- if I extract more than 22% I will have a drink in the cup defined as over-extracted.
To be precise and aware of the extraction percentage, there are specific tools, but if you are not a great expert in the sector it is useless to buy, given the high prices.
Let’s therefore rely on our senses to learn to recognize under or over extraction!
We take for example espresso, as it is the easiest to recognize even just by looking at it:
1. In the first line above we see an under-extracted coffee.
As the word itself says, we have extracted too few substances from our coffee bean, making the final drink very dull.
In particular we will see:
- The pale cream, tending towards white and already practically “pierced”, thus allowing a glimpse of the dark drink underneath.
- On the palate, however, the coffee will be dull, with a flat and not very intense aroma and above all a bad and very unpleasant acidity will prevail.
- Finally the drink will have no body. If we swirled the coffee between the tongue and the palate we would not feel any density.
If you are not preparing an espresso you will not have the cream to help you, so rely on the taste and try to understand if it is balanced and good, or if on the contrary it only has a strong and really annoying acidity, without other aromatic notes.
2. In the third and last line at the bottom we see an over-extracted coffee.
As the word itself says, we have extracted too many substances from our coffee bean, making the final drink too full.
In particular we will see:
- The very dark cream.
- On the palate, however, the coffee will have a less complex aromatic profile, in which we would only perceive empyreumatic (burnt) hints. The dominant taste will be bitter.
Again, if you’re not making espresso you won’t see the crema so taste it and find out if it’s really too bitter, without much else to offer.
3. Finally, in the central row we see a correctly extracted coffee.
We have therefore extracted the right number of substances for a balanced, intense, full-bodied cup with an incredible aromatic profile!
In particular we will see:
- The hazelnut colored cream, shiny and smooth, without micro or macro bubbles, and which persists for at least 1 minute after extraction without “piercing”.
- On the palate, however, the coffee will be excellent, with a wide and tasty aromatic range, with notes of chocolate, caramel, vanilla, toast, honey, flowers, fruit, citrus fruits and much more! It will then be intense and above all you will notice a delicate and pleasant bitterness, a more or less marked and enveloping acidity, balanced by a more or less intense dose of sweetness. Finally the drink will have a good body. If we swirled the coffee between our tongue and palate we would feel the density of the drink. INHow much does grinding influence the success of the extracted coffee?! In the end, dWhat is the grinding affected? Grinding is influenced by many variables, such as: The coffee you purchased, its freshness, composition and storage; The tool you selected for extraction: espresso, moka, paper filter, percolation, pressure, infusion, etc.; External environmental conditions; The water used: temperature and molecular composition; and much more. Without going too much into the technicalities, let’s aim directly at what is most important for us at home or at the bar: the tool we are using to prepare the coffee. Each tool requires its specific grain size, i.e. size of the ground material. Why? Because the contact time depends on the grinding.And contact time defines an under- or over-extracted drink, as we saw previously. Let’s explain the theory behind this statement: Different squares, representing equally sized ground coffee grains, with blue spaces, representing contact with water. Starting from the left: 30 seconds of contact between water and coffee, 120 seconds of contact and 240 seconds of contact. Let’s assume that each grain of the coffee we ground is as large as these 3 squares above: If the water passes through the ground coffee for just 30 seconds, as in the first case on the left, it manages to penetrate the grain just a little. All the substances that are therefore found in the center of the grain will not be brought into the cup, consequently making the coffee under-extracted. Same thing if we let the water flow for 120 seconds: the water would be able to penetrate deeper, but not yet completely. The coffee is therefore still under-extracted. While the correct extraction will take place in 240 seconds. Now let’s take the opposite example: Different squares, representing ground coffee grains of different sizes (smaller on the left, larger on the right) with blue spaces, representing the contact with water for 120 seconds, and other red spaces, representing the over-extraction of the beverage. This time we pass the water through the ground coffee for 120 seconds, but changing the size of the ground coffee: In the first case we have a very fine ground coffee: if the water passed through it for 120 seconds, not only would it reach depth, but it would also extract too much, making the coffee over-extracted. In the second case, however, we have a medium ground coffee, perfect for an extraction time of 120 seconds. Again, however, in the third case the grain is too large and in 120 seconds the water does not do its job well, making the final cup under-extracted. Given that each tool for preparing coffee has its own specific extraction principle (percolation, infusion, pressure, boiling or a hybrid of these) and therefore its own specific recipe and extraction time, we must adapt the size of our ground coffee to make so that the final drink is always good and pleasant! Find out more in another article: https://www.caffeernani.com/come-preparare-il-caffe/diverse-macinature-per-diversi-metodi-di-estrazione/ Finally, I leave you with other interesting references to complete your knowledge on grinding: https://youtu.be/YBebSRzM9dw Which coffee grinder should I buy for my home?https://www.caffeernani It will then be intense and above all you will notice a delicate and pleasant bitterness, a more or less marked and enveloping acidity, balanced by a more or less intense dose of sweetness.
- Finally the drink will have a good body. If we swirled the coffee between our tongue and palate we would feel the density of the drink.
How much does grinding influence the success of the extracted coffee?!
In the end, dWhat is the grinding affected?
Grinding is influenced by many variables, such as:
- The coffee you purchased, its freshness, composition and storage;
- The tool you selected for extraction: espresso, moka, paper filter, percolation, pressure, infusion, etc.;
- External environmental conditions;
- The water used: temperature and molecular composition;
and much more.
Without going too much into the technicalities, let’s aim directly at what is most important for us at home or at the bar: the tool we are using to prepare the coffee.
Each tool requires its specific grain size, i.e. size of the ground material.
Why?
Because the contact time depends on the grinding. And contact time defines an under- or over-extracted drink, as we saw previously.
Let’s explain the theory behind this statement:
Different squares, representing equally sized ground coffee grains, with blue spaces, representing contact with water.
- Starting from the left: 30 seconds of contact between water and coffee, 120 seconds of contact and 240 seconds of contact. Starting from the left: 30 seconds of contact between water and coffee, 120 seconds of contact and 240 seconds of contact.
- Let’s assume that each grain of the coffee we ground is as large as these 3 squares above: All the substances that are therefore found in the center of the grain will not be brought into the cup, consequently making the coffee under-extracted. Same thing if we let the water flow for 120 seconds: the water would be able to penetrate deeper, but not yet completely. If the water passes through the ground coffee for just 30 seconds, as in the first case on the left, it manages to penetrate the grain just a little.
- The coffee is therefore still under-extracted. While the correct extraction will take place in 240 seconds.
Now let’s take the opposite example:
Different squares, representing ground coffee grains of different sizes (smaller on the left, larger on the right) with blue spaces, representing the contact with water for 120 seconds, and other red spaces, representing the over-extraction of the beverage.
- This time we pass the water through the ground coffee for 120 seconds, but changing the size of the ground coffee: In the first case we have a very fine ground coffee: if the water passed through it for 120 seconds, not only would it reach depth, but it would also extract too much, making the coffee over-extracted.
- In the second case, however, we have a medium ground coffee, perfect for an extraction time of 120 seconds.
- Again, however, in the third case the grain is too large and in 120 seconds the water does not do its job well, making the final cup under-extracted.
Given that each tool for preparing coffee has its own specific extraction principle (percolation, infusion, pressure, boiling or a hybrid of these) and therefore its own specific recipe and extraction time, we must adapt the size of our ground coffee to make so that the final drink is always good and pleasant!
Find out more in another article:
Finally, I leave you with other interesting references to complete your knowledge on grinding:
Which grider would be better at home?
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