Over-extracted or under-extracted coffee: Causes and Useful Advice

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22 June 2020
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Over-extracted or under-extracted coffee: Causes and Useful Advice

caffè sovraestratto o caffè sottoestratto

The Perfect Espresso, we know, is an art. And every bartender in the world has its own little secrets.
But the risk of tripping over or under-extracted coffee is always just around the corner.

So what do you do?
“How’s this espresso?” “Good!” This is one of the most subjective expressions in the world of coffee, expressing personal appreciation, but nothing says under the following aspects:

  • technical
  • organoleptic
  • sensory

How can you tell if an Espresso is Balanced?

Describing an Espresso is very difficult, but it is even more difficult to understand and define if it has been extracted correctly, i.e. if we are drinking a:

  • Balanced Espresso
  • Under-extracted Espresso
  • Over-extracted Espresso

Causes of Over-extracted Coffee

Over-extracted coffee is an espresso in which too many elements have been extracted from ground coffee, i.e. both the positive and negative components. In this case, the popular saying ” too much of a good thing” applies.

The causes may depend on several factors. Let’s take a few examples:

Too Fine Grinding
If the grinding is too fine, the percolation is too slow, drop by drop, as the water will not pass easily through the ground coffee. As a result, the water stays in the filter for a long time, extracting too many components of the coffee, not only positive but also negative.
In the cup you have a coffee with the typical characteristics of an over-extracted Espresso:

  • full-bodied
  • intense flavour
  • strong
  • burnt aromas

Excessive Amount of Coffee in the Filter
Putting too much coffee in the filter causes over-extraction, because, even in this case, the water finds it very difficult to pass through the ground coffee, “cooking” it for too long and also extracting bitter substances. When you taste the coffee, you will mainly smell burnt.

Causes Under-extracted Coffee

Undextracted coffee, on the other hand, is an espresso in which not all the positive organoleptic characteristics have been extracted from ground coffee.

It is therefore not a complete espresso, which hasn’t shown its full potential.

Also in this case the causes can be many, so let’s make some examples:

Too Coarse Grinding
With too much grinding the percolation is too fast, so the water will not extract enough positive substances. The consequence is that in the cup you have a typically under-extracted espresso, that is:

  • watery
  • low in flavourings

Insufficient Amount of Coffee in the Filter
If the dose of coffee in the filter is lower than normal, the result is under-extracted coffee due to the fact that the water pass too easily through the ground coffee and, consequently, it is impossible to extract all the positive components.

Espresso Ristretto and Espresso Lungo

Speaking then of the quantity of espresso in the cup, the latter defines 2 typical examples of over-extracted coffee and under-extracted coffee:

  • Long Espresso
  • Espresso Ristretto

A Long Espresso is generally obtained by allowing the extraction to continue for longer than normal, therefore, after having extracted the positive parts, it will begin to percolate some yellowish liquid that adds hints of bitterness and astringency, typical of a Long and Over-extracted Espresso.

A Ristretto Espresso, on the other hand, is an extracted Espresso with all the correct parameters, including grinding and quantity in the filter, but in which the extraction is interrupted earlier than normal.
In this case you have in your cup a short, dense, full-bodied espresso with an intense taste and strong flavour. We call it under-extracted because, probably, not all the positive components have been extracted from the ground coffee.
In fact, it should be underlined that a strong and intense espresso is not always due to an over- extraction of the coffee!

In conclusion
Many other parameters can influence the extraction of an espresso.
The bartender’s competence is therefore essential in order to consciously control all the steps.

Remember, your goal is for your customer to say: “As good as ever!”. And not: “Today the coffee turned out particularly good!”.

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