Ground Coffee

Marco Polo is one of the best-known travellers and merchants, even though his travels took place in the 13th century. During his many trips, which led him to travel around Asia, especially present-day Mongolia and China, Marco Polo always traded.

He travelled along the Silk Road and one of the most precious goods that were traded along this route were spices: pepper from India, cinnamon from Ceylon or ginger from China. Spices and coffee share a common history, that of intercontinental trade.

But also something else, if you grind them before using them, they lose properties. That is why ground coffee was not suitable to be transported from one place to another then and is still not suitable now.

And that’s what this post is about: why it is better to grind the coffee beans just before we are going to brew them and how to do it to keep all its properties and brew them correctly.

Coffee seedling
Coffee seedling
It may seem like a redundant question, but it is not. Coffee is the seed of the coffee tree.

That is, it is a grain-shaped seed like many others. But when grinding them and brewing them with water, we obtain a drink that has very particular organoleptic qualities.

All stages of the coffee process are important.

The coffee grower who chooses a particular land and location to plant, the type of coffee plant chosen, the way they are grown and harvested, how are they dried, transported, roasted and packed, all leave a mark on the coffee seeds.

Throughout this process, the coffee has been (or should have been) kept as a whole bean to maintain all its organoleptic qualities.

But once it’s about to be brewed, the coffee must be ground. How we grind it, which tools we use, with what size and when, is a very important part of this whole process, but one that many people do not pay enough attention to.

When we talk about ground coffee, we are speaking about why it is important to keep the coffee beans whole until the last moment, what tools to use when grinding them, what size should the ground coffee have, how to preserve it and prepare it.

All this is to make sure that we do justice to the work of so many people before us and above all, that we enjoy each cup of coffee to the fullest.

Why is it important to keep coffee beans ungrounded until brewing them?

Ripe fruit due to oxidation
Ripe fruit due to oxidation
Because of oxidation. This is the main reason why we should grind the coffee only before using it. And you may be wondering, but does coffee rust? Well yes, it does. Every organic compound oxidizes when it comes in contact with oxygen. It is the reason why a fruit ripens, changes colour and rots.

Oxidation, at the molecular level, happens because oxygen molecules steal electrons from other molecules and the molecules that lose them become unstable and reactive. This causes the molecular composition of the organic compound to change, in this case, coffee. And, therefore, their organoleptic properties also change.

Coffee beans have oils, chemicals, and acids that are soluble when they come into contact with water. These soluble elements are what give this drink its particular colour, flavour and aroma. If these elements are degraded before the extraction, then the resulting drink will be of poorer quality. That is, it will lose part of its organoleptic qualities.

These qualities are given by factors as diverse as the place of origin, the altitude, the climate, the type of plant, the type of drying, washing and roasting. At each of these stages, everyone involved has ensured that all processes highlight the unique qualities of each bean. If we grind the coffee well in advance brewing it, we will be having the opposite effect, we will be damaging those qualities.

That is because when we grind the coffee, we are expanding the surface of the coffee molecules that are in contact with oxygen and, therefore, accelerating the oxidation process.

Although it is necessary to ground the coffee before brewing for a correct extraction since it is the only way in which the solubles dissolve, the best time to grind it is just before brewing.

Theory of extraction

Ground coffee bed to prepare a V60
Ground coffee bed to prepare a V60
Once we have established that coffee must be kept whole until extraction time, and before continuing to see how we grind it, with what tools and how we preserve it, we are going to speak about two important topics as a theoretical basis: the theory of extraction and the size and distribution of the grind.

The theory of extraction refers to how we extract the coffee solubles when they come into contact with water and to the amount of solubles that are dissolved once we have finished. As Ted Lingle says in The Coffee Brewing Handbook:

The extraction is a measure of the amount of soluble in the final drink. It is also expressed as a percentage, comparing the amount of coffee solid material in the beverage with the amount of ground coffee used to prepare it. Approximately 28% of the organic and inorganic matter contained in roasted coffee beans will easily dissolve in water. The remaining 72% is fibre cellulose from the seed, which is not soluble in water under normal processing conditions ”.

Although it is only 28% of the coffee that is dissolved in the water when we prepare the drink, this 28% is made up of approximately 800-1000 natural flavourings, half of them soluble solids and the other half gaseous and/or volatile aromas. These compounds are what give each cup of coffee so much complexity.

When we talk about extraction theory, we refer to the extraction percentages, which are related to the method we use to carry out the extraction -filter, espresso, immersion-, in relation to the number of soluble substances dissolved in the final drink.

This is important because, depending on the method, we will need a grinding size or another to achieve the desired extraction percentages.

TDS measurement

Reading of disolved solids in a coffee with a refractometer
Reading of disolved solids in a coffee with a refractometer
The second part of this theory has to do with Total Dissolved Solids (TDS). The TDS is a measurement that helps us know what the percentage of solids is in a cup of coffee. That is to say, of a 200 ml cup of coffee, what percentage is water and what percentage is coffee (or other common water solids).

So, on the one hand, we have the percentage of potential soluble substances that can be extracted from a coffee (which maximum is 28% of each bean) and on the other, we have the total percentage of dissolved solids in each cup of coffee, which varies depending on the method used, the desired drink and the technique and precision of the barista.

The percentage of dissolved solubles in a coffee that professionals work with, have discussed and experimented with so far is between 18% and 22% of the possible total (28%).

Although this has been recently changing with new advances, better-developed coffee roasts and using more controlled forms of extraction. The percentages have been pushed above 22% with very positive results. We could say that the coffee vanguard now moves from 18% to 27% with excellent results.

These would be normal percentages depending on the method:

  • Filtered: 1.2% – 1.6% (TDS)
  • Americano, long black: 2% – 5% (TDS) (depends on the amount of water added)
  • Lungo: 5% – 7% (not a common drink) (TDS)
  • Espresso: 7% – 10% (TDS)
  • Ristretto: 10% – 12% (TDS)

For a cup of coffee to be balanced and to show all its qualities, between 18% and 22% of all the solubles must have been dissolved and this must represent a percentage of between 1.2% and 12% of the total solids in each cup.

If these percentages are above or below the average, we will have a cup that may be under or over-extracted. Both results are not advisable, since in the first the coffee will not have all the possible aromas and flavours and in the second we will have extracted too much and the bitter and other undesirable notes will hide the desirable tasting notes.

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    La Nueva Montaña – Guatemala – Natural

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Grind size

Mahlkonig profesional coffee grinder
Mahlkonig profesional coffee grinder
And we can ask ourselves, what does all this have to do with ground coffee and the type of grinding? Well, among the parameters that we have to control to obtain a correct cup of coffee, once we have roasted coffee, the two most important maybe the size of the grind and the ratio of water/coffee.

To obtain a correct extraction, and we have already defined what we mean by this, one of the most important elements is that the size of the coffee grind is in accordance with the method that we are going to use so that the extraction occurs within the percentages that we have mentioned.

Let’s say there are three general ways to brew coffee: Immersion (French Press) percolating/filter (AeroPress, V60, Kalita, etc.), and espresso.

Depending on the extraction method (immersion, percolating/filter or espresso) and the technique (AeroPres, V60, espresso) we will use one grind or another. This is a general ratio:

  • Espresso: very fine grind (almost like flour)
  • Mokka: fine grind (as fine salt)
  • Aeropress: medium grind (slightly coarser than fine salt)
  • V60: medium grind (slightly coarser than fine salt)
  • Chemex: medium grind (slightly coarser than fine salt)
  • Plunger: coarse grind (like coarse salt)

And we’ll just briefly mention the coffee/water ratio: most brew ratios for immersion and percolating/filter are between 1:10 and 1:18. With the notable exception of espresso, which is between 1:1 and 1:3 due to faster and more efficient extraction.

This ratio means that for each gram of coffee we would use between 10 and 18 grams of water for immersion and percolating/filter and with the espresso method, for each gram of coffee we would obtain between 1 and 3 grams of drink in a cup.

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  • Comandante Hand Grinder is a powerful, hand coffee grinder, with an advanced conical burr set design with a stainless steel body and high-nitrogen martensitic steel burrs.

    Comandante Hand Grinder C40 MK4

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  • Timemore Chestnut C2 Manual Grinder.

    Timemore Chestnut C2 Manual Grinder

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  • Hand Grinder HARIO Mini Mill. A freshly ground coffee with a suitable grind size for the brew method that we are going to prepare...

    Hand Grinder HARIO Mini Mill

    33,00 VAT included

Grind distribution

Preparation of coffee with the Kalita technique
Mahlkonig profesional coffee grinder
Finally, we still need to talk about the distribution of particles in the grinding. When we grind coffee, not all the ground particles are the same size. Within a range, some particles will be very fine and others that will be very coarse.

The unit we use to measure coffee particles is microns. When grinding coffee, a grinder will give us particles of many different sizes: from particles of one micron to others of one thousand five hundred microns. Although we will generally divide them into those that are below 100 microns, those that are about 400 microns in size and those that are about 800 microns.

No grinder will give us a grind where all the particles have the same size, but they will be within a margin. This is what we call “grinding distribution”. The better the grinder, the less margin in the distribution and the worse it is, the greater the margin and the disparity of sizes.

This is important because when carrying out the extraction what we are looking for is that the ground coffee is as homogeneous as possible, that is, that all the particles are within a small margin.

If this is not the case, if there are particles that are very different in size, the extraction will not be uniform and the result can be an over-extracted and under-extracted cup at the same time (large particles have not dissolved all the solids they should and small ones have dissolved more than they should).

Synthesis of the grinding theory

Different preparation methods require different grinding
Different preparation methods require different grinding
To simplify this whole theory a bit and make it more practical, we can establish the following parameters (at the cost of losing a bit of accuracy):

A finer grind results in a slower water flow which results in a longer contact time between water and coffee and therefore a higher extraction.

Conversely:

A coarser grind results in a faster water flow resulting in shorter water-coffee contact time and therefore less extraction.

And:

For the immersion methods, we will use a coarse grind, for the percolating/filtering finer and very fine for the espresso.

How to grind coffee

Now that we are aware of the importance of maintaining coffee beans whole and grinding them correctly, how do we grind coffee?

The answer is simple, but with several possibilities. Obviously, we will need a grinder if we want to grind it at home. The coffee grinders can be manual or electric.

We recommend using manual grinders at home (unless you want and can spend several hundred euros on a professional electric coffee grinder). That is because commercial electric blade grinders do not grind the coffee, but smash it and also heat it (due to the friction of the blades and the motor).

Most low-end electric grinders will give us a very wide grinding distribution margin, which is not recommended.

Commander and Timemore brand manual coffee grinders
Commander and Timemore brand manual coffee grinders
Manual coffee grinders usually have conical ceramic grinding wheels, which grind the coffee and it falls into a separate compartment, which helps a more homogeneous grind.

In our shop, you may find several models with different prices. The Comandante manual coffee grinder is one of those we highly recommend. And this HARIO Mini Mill is also very good if your budget is not so bulky.

Lastly, if you don’t have a grinder yet, you can buy your coffee beans and ask your local coffee shop to grind them. It is not our recommended method, but if you preserve it well and consume it in a short period, it should not lose too many properties.

How to preserve ground coffee

We will always recommend keeping coffee beans whole until we are about to brew them, but we understand that there may be situations in which this is not possible. That is why we are going to give some recommendations on how to preserve ground coffee.

If you are going to buy coffee and you don’t have a grinder, then ask to have it ground according to the brewing method and technique you are going to use. Ask for it to be packed in a bag that can be vacuum sealed and has a one-way valve (the bags in which good coffee beans are packed are usually like this).

Once at home, store it away from sunlight and strong odours and in an airtight container. Lastly, consume it within a week or ten days.

By following these simple instructions, you can continue to enjoy your coffee, even if it has been ground for a while.

How to prepare ground coffee

Preparation of coffee with the Kalita technique
Preparation of coffee with the Kalita technique
Ground coffee can be prepared using three different methods: immersion, percolating/filter, and espresso.

Each method has several techniques. The most popular immersion method is the French press, but so are the AeroPress, the siphon, the Clever, and cupping. In the filter methods, we find the V60, the Chemex and the Kalita, but also the electric drip coffee machines such as the Behmor Brazen coffee machine. And the espresso method is essentially based on an espresso machine.

Regardless of the method and technique, the main idea is the same: that the water is in contact with the ground coffee for a time and in a particular ratio (we have talked about both before).

How to make ground coffee without a coffee maker

And you may ask yourself, can you make ground coffee without a coffee maker? Well, yes, you can, although we have to be much more careful so that it brews correctly.

A very common way of doing this which we recommend for summer is the Cold Brew, or cold extraction. For that, you will not need a coffee maker, but you will need a container and gauze. If you are interested, in this post we explain how to do it step by step.

Another way is to do it the old-fashioned way, pot-coffee, and although a bit rudimentary, it can get us out of trouble. It is quite straightforward and resembles an immersion method. We need the coffee to be coarsely ground and an amount of water that gives us a ratio/proportion of about 15 grams of water for each gram of coffee. Apart from this, a pot and a strainer (if we have one).

To do this we bring the water to a boil, turn it off and wait about two minutes. Then we add the coffee and stir carefully. We wait about 4 minutes and we serve it with a strainer, or we decant it. You will be able to enjoy an acceptable coffee without a coffee maker.

What is the best ground coffee and where to buy it?

Ground coffee bed to prepare a V60
Ground coffee bed to prepare a V60
The best ground coffee will always be the best coffee beans. And the best coffee beans are those which have been processed with care since it was planted and follow the guidelines of what we understand by specialty coffee.

This implies that the coffee is fresh, in season and recently roasted. If we want a coffee in optimal conditions, we must consume it within twelve weeks after being roasted, if it has been preserved correctly.

The type of roast, whether it is a lighter or darker roast, will depend on our tastes and preferences. But we shouldn’t buy a coffee that is too roasted or burnt since we will be losing organoleptic qualities.

You can buy ground and whole coffee in our store or go to your favourite specialty coffee shop.

Ground coffee vs coffee beans

Should you buy coffee beans grounded or whole? We hope that this post has answered this question: it will always be advisable to buy coffee beans and grind them only before using them to avoid oxidation and degradation of its organoleptic properties.

We have discussed the theory of extraction and the size and distribution of grinding particles. In this regard, to achieve extraction percentages (between 18% and 22%) and TDS (between 1.2% and 12% depending on the method), the grinding must be adjusted to the brewing method as homogeneous as possible. The water/coffee ratio is also important.

For correct grinding, we recommend using a manual coffee grinder at home. And only in situations in which we have no other alternative, buy it whole and ask for it to be ground.

In all cases, but especially if the coffee is ground, conservation is very important. We should ensure that it is in bags with hermetic and vacuum closure and with a one-way valve.

And when preparing it, the size of the grind will depend on the method that we are going to use. But generally speaking: a coarse grind for immersion methods, fine for percolating/filter and very fine for espresso.

All this so that we can enjoy our coffee to the fullest and do justice to the work of all those who have worked hard to ensure that each coffee bean reaches us in optimal conditions.

Now that you know all this … you just have to choose which coffee you would like to taste.

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