Have you ever wondered why your coffee tastes bad on a particular day? Or if there's a word to describe it? The answer is yes, it does. In the world of coffee, there are two very important terms: over-extraction and under-extraction. What do they mean? In this article, we explain.
Under-extraction in coffee
It's difficult to quantify under-extraction without the proper equipment, but in terms of flavor, we talk about under-extraction when we haven't extracted enough flavor from the beans, especially the compounds that could give it balance and added sweetness. The beverage presents acidic and herbal flavors, low sweetness, perhaps a bit of saltiness (particularly in espresso), and a very short aftertaste. These are the most obvious indicators of under-extraction.
It's important to clarify that the compounds responsible for these undesirable flavors also exist in a balanced-tasting beverage. It's just that the balancing compounds are extracted later and mask the undesirable flavors.
A common mistake when describing flavors is confusing the concepts of "acid" and "sour." They are two different things, although many people interpret them similarly, and in many languages, they are considered practically the same thing.
In coffee, we talk about "sour" as something undesirable. A very intense acidity that triggers an immediate physiological reaction, like when we eat very acidic lemons.
Acidity, while it can also be good or bad, is more of a category of flavors. We talk about a coffee with "juicy acidity," "a green apple acidity," or we say "sharp and sour acidity."
If you're brewing coffee at home, working at a coffee bar, or cupping coffee and find that your coffee tastes similar to the one described above, it's probably under-extracted. We recommend that you try a finer grind, a longer brew time, or a higher water temperature for your next brew. Change one variable at a time and see what effect it has on your final beverage.
Over-extraction in coffee
Contrary to under-extraction, in over-extraction we remove more soluble material than we would like, which also results in undesirable and unfavorable flavors.
The main characteristics are intense bitterness and astringency or dryness in the mouth. To understand the meaning of "bitter," we can refer to products such as tonic water, pure caffeine, or Campari.
Caffeine is understood to be one of the main causes of bitterness in coffee, but other chemical compounds within the coffee bean also contribute to this taste, such as other acids (e.g., chlorogenic acid) and carbohydrates. Distillation and the degradation of sugars, due to darker roast profiles, also generate bitter flavors.
Astringency or dryness in coffee is generally a bad and undesirable thing. To understand this sensation, we can refer to unsweetened black tea, which causes the inside of the mouth to feel dry and rough, like sandpaper.
If you get any of these flavors in your home brew, it could mean your coffee is over-extracted. Next time you make coffee, try using a coarser grind size, shortening the brewing time, or using a lower water temperature. Make sure to change one thing at a time and see what effect it has on your brew.
Ideal coffee extraction
A well-prepared coffee, which meets industry-established standards of extraction between 18% and 22%, should be sweet, creamy, and well-defined with fruity attributes and flavors. The aftertaste is also a good indicator of a good brew if it is long and pleasant.
Above all, a well-prepared coffee is a coffee with a balance between its main attributes, such as aroma, acidity, sweetness, body, and aftertaste.
How to fix pre-brewed coffee
If you've already made the mistake, there are still ways to save your coffee, although the flavor won't be the same.
For under-extracted coffee: Quickly pass the brewed coffee through the coffee grounds again. If necessary, add a little more grounds and a little more hot water. Your best option would be to reuse the coffee grounds by blending them with tea.
For over-extracted coffee: Use sugar and baking soda. The sugar cancels out the bitterness, while the baking soda neutralizes the overwhelming acidity of over-extracted coffee . You can always add plenty of milk or cream to create a completely different drink.