On this page we’ll provide you information on the details of coffee extraction, the process of coffee solubles being pulled out of the beans and into the water. The different stages of each category of coffee compounds being extracted impact the flavor of the coffee, so this guide will tell you what you need to know about the impact of the extraction process on the character and quality of the coffee.
Understanding Coffee Extraction to Create Balanced Flavours
Crafting a great cup of coffee is ultimately a question of achieving the right balance.
Any given coffee extraction process is going to consist of different stages where balance in flavor can be managed and shaped as each stage releases different chemical compounds.
If any of these stages are overlooked or minimized then the balance and flavor profile will be impacted negatively.
Consider that many people assume that a coffee that tastes too strong is also “over developed”. In truth, as the brewing chart demonstrates, coffee can actually taste very strong and the root cause can be that it is in fact “under developed”.
This misconception is caused by the assumption that the development of the coffee refers to its “strength” when in fact it refers more to its flavor as well as all the different compounds that are unlocked during the brewing process.
The Coffee Extraction Process
To elaborate: Different coffee solubles are extracted during distinct phases of brewing, and a low extraction yield will often result in mainly the later stage solubles not being extracted.
So the under extraction only impacts specific solubles and this will create an unbalanced flavor profile.
Let’s say a typical extraction yield for a cup of “regular” coffee was measured at roughly 25%. This would result in too high a percentage of coffee and would be considered over extracted.
Extraction and Total Dissolved Solid (TDS) Ratio
An espresso shot would have an extraction yield of maybe 16.5% which is well under the limit where we would consider the coffee to be “over extracted” but because it contains much less water the strength (not the flavor) might be much higher than our 25% extraction “regular” coffee example.
The espresso has a higher TDS, even if the percentage of soluble coffee that was extracted is lower. Thus, it is the “stronger” coffee.
Strong but under developed coffee is often attributed to having too much coffee brewing for too limited an amount of time.
The coffee that normally dissolves in the later stages of the extraction process doesn’t get the opportunity to be released and extracted. So having a lot of this poorly extracted coffee solution mixed with only a little water just results in a coffee that has a very high proportion of first stage (“unfinished”) solubles.
The mirror to this scenario is having coffee that is produced by releasing a high percentage of the total available solubles (somewhere in the range of 25% let’s say) making the coffee bitter.
Even if you lower the TDS by adding more water you’ll only end up with a coffee that tastes both weak and bitter.
Did You Know?
You can tell when a coffee has been under extracted as it will lack overall flavor. The coffee will taste less complete and full of flavor and you’ll be left with a brew that is less complex and slightly bitter due to the sweeter flavors not having had a chance to be “pulled in”.
How do you fix over extracted coffee?
Over extraction suggests two possible tweaks need to be made to your coffee making process. Either the grind is too fine, the time you left it to brew is too low, or some combination of both.
Can you over extract espresso?
It’s perhaps harder to do than other coffee types, since espresso aims to have pretty concentrated extraction levels, but you can leave the coffee grounds to heat up for too long and over extract, leaving you with an espresso that tastes dry and bitter.
What would occur if the extraction is too slow?
If an extraction takes longer than ~30 seconds it will result in a coffee that is typically flat and bitter. This can happen when the coffee grounds are packed too tightly together, without leaving enough room for the water to penetrate through. This would be a sign that the coffee grounds are too fine and need to be made coarser.