Extraction I

The other day a colleague asked me about the famous 1:2 ratio for espresso , how fashionable it seems to be, and the reason for its choice. If it is a guideline established by some SCAA type association, if it is an idea taken on the sleeve by some barista and repeated in an industry that tends to imitate itself itself, or if, on the contrary, it has its meaning and explanation. To To understand it we have to go back to one of the most difficult aspects of understand, but more important to enjoy a good coffee, the extraction .

Roasted coffee is soluble in a varied percentage which depends, fundamentally, on the type of grain and roasting that has been done. applied, although it ranges between 27 and 30% . That percentage is made up of different solubles such as sugars, acids, alkaloids and salts, and the rest of the coffee is indissoluble organic matter (cellulose, fiber and oils). This tells us that if we squeezed a certain dose of coffee to its limit, it could lose 30% of its mass once extracted.

As experience will have taught you, extract all the soluble contained in a certain coffee gives us a horrible cup and this is why Therefore, the baristas cut the extraction at a certain point , to put only those that are pleasant to us in our mouths. The chose from that moment is the Holy Grail of our guild and the topic we are going to to dedicate this series of publications.

How much has to be extracted?

Not just how much, but how. We must know that the different solubles that that make up coffee are extracted at different times and conditions, so Depending on how we carry out the extraction we will have dragged different flavors. The acids and salts in coffee are quickly dissolved on contact with water, the sugars that will add sweetness to the cup will be extracted throughout the entire extraction in a more leisurely manner and the components bitter too.

With this in mind, we enter the realm of established guidelines by institutions such as SCAA, SCAE or The Norwegian Coffee Association , which recommend that we extract between 18 and 22% of our total dry coffee dose. This choice is based on a study carried out in the 60s by The Coffee Brewing Institute on the general taste of the American population, but it is still current since below or above this range we find normally unpleasant drinks.

Within these parameters it is still possible to spin fine lines and for this we will dedicate Future posts where we will try to explain what percentage is best for every coffee. For the moment, we will say that between 18 and 22% will be our sweet spot or optimal extraction point , where our coffee is most likely to taste sweet, like ripe fruit, transparent and with a pleasant and complex acidity. Below this range we will have an under-extracted coffee and above that an over-extracted one.

Underextraction and overextraction.

Care must be taken with these definitions since it is usually relate a weak coffee with an underextraction and a strong one with a overextraction and this is not always the case. An under-extracted coffee is simply that from which we have obtained less than 18% of its soluble content, and one overextracted from which we have taken more than 22%.

bitter-taste-guy-121008 An underextraction is characterized by its strong and unpleasant acidity *, and for its salty notes. It has no sweetness and its aftertaste is very short. It's basically like sucking on lime and salt, but without the shot of tequila. The underextraction is one of the main problems we find in the espressos from specialized coffee shops, usually because they want differentiate itself from a dark and bitter past, but which still does not find a nice drink that you can drink without looking like a chimpanzee. With the new generations of roasters and specialty coffees this is no longer necessary.

*There is an exception to these characteristics and that is that in the case of channeling or tunneling effect can lead to bitter underextraction. Certain areas of the coffee would be overextracted but the entire initial dose would be underextracted.

Overextraction is identified by its bitter and astringent taste. We have squeezed the coffee for above its possibilities and we will find an unpleasant bitterness, nothing similar to the bitterness of caramelization, but rather similar to that of a burnt product. Typically, overextraction is related to weak drinks due to the amount of water that has passed through coffee and its finish is dry and astringent. Does it sound familiar to you? It is the coffee that You can drink it in 99% of traditional coffee shops.

The sweet spot: the search for sweetness and its risks.

At Hola Coffee we always seek to make our coffee as sweet as possible for Our mission is to extract the greatest amount of sugars possible without that the bitterness comes to cover the other flavors. No need to explain what sweetness is, although in coffee it will always be subtle, similar to that of the fruit, and that over time it becomes more easily identified.

With small or worn teeth it is very difficult to pass the 20% extraction level. without some areas being over-extracted and our coffee tasting bitter, therefore than with the mills that are generally used in hospitality (even in the most specialized) we should aim for 19-20%. (We'll go into grinding further later.) Special care must also be taken in the dosage, distribution, pressing and placing the filter holder in the group, to avoid have channeling, where the water would mostly pass for a specific area and over-extract it.

The strength or concentration of the drink = solids dissolved in the coffee.

It is very important to understand this concept, since it is closely linked to that of extraction. The concentration of the coffee drink is, simply, the percentage of solids that have dissolved in the water we have used, that is, how much percentage of coffee is there per water.

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In order to analyze this variable, a calibrated refractometer is needed. for coffee (there are various commercial brands). This thing It will say the % of dissolved solids in our drink or TDS (total dissolved solids) , so the undissolved ones must be filtered first. To make us a idea, an espresso is around 9-11% TDS and a filter coffee between 1.1 and 1.5% to have a nice drink. We know this because thanks to this data we can obtain the extraction percentage of the coffee using the following formula:

% Extraction = (TDS x Mass of the drink) / dry dose mass

With the result of this operation we already have an idea of ​​where we are headed. we are moving It is important not to become obsessed with mathematics and First of all, we want our coffee to be delicious, but these formulas help us to know what variables may be failing us in a recipe concrete, and they also give us objective data.


With the Brewing Control Chart* we can graphically know where our coffee is. In On the abscissa axis we have the extraction percentage and on the ordinate axis we have the strength or concentration. SCAA tells us the comfort zone for our coffees and what can we expect from them if we are outside of it.

*Important: the box is designed for filtered coffees, if we want it apply to espresso, the concentration or strength must be calibrated between 8 and 12%.

The VST application for iPhone called CoffeeTools . It is paid but it is working usually in these terms it is very useful as you can always have it on you and quickly understand which variable you need to touch to improve your recipe.

Bathroom scales.

There are still baristas who resist using scales in their daily lives. with coffee. Although they use them to make their filter coffees, they are reluctant to apply them to the preparation of espressos. I'm not going to make a list why it is necessary to use them in order to improve and be constant in the preparation of espressos, but all of the above is impossible to access without a scale that weighs the dose of dry coffee and the drink. If you add to this that the grinders are not constant and coffees vary in volume depending on their freshness, you can now throw away your old measuring cup.

And what is all this for me?

It may all seem very abstract and we have not answered the question we are asking. my partner did to me, but it is necessary to understand these concepts to be able to look for the most appropriate recipes and methods for each coffee. For now we will stop here so as not to saturate us.

In the following posts we will see what variables make us extract more or less and we will analyze the ways to approach a coffee to get the best out of it.

Until next time!

Pablo Caballero

TDS barista café de especialidad cafés especiales espresso extracción ratio refractómetro specialty coffee