You may already be familiar with the term extraction in coffee. Essentially, it’s used to describe the removal of flavoring material from roasted coffee that is dissolved into water. Things that can be dissolved into water are referred to as water soluble, and roasted coffee is about 30% water soluble (the remaining 70% is mostly cellular fiber and other insoluble compounds). Still with me? The hard part is almost out of the way.

Over- vs Under-Extraction

Research into taste preferences over the years suggests that we like to drink coffee that contains 18-22% of the water-soluble flavoring material available in coffee. If we extract less than that, then we have some of what we like, but enough to create a balanced, tasty brew. This is what we can under-extraction. Under-extracted coffees generally taste grassy, sour, lacking in sweetness or even peanut-like. This is because acids in coffee are really easy to extract, so they come out first while other compounds that help sweeten the cup take more energy.

On the other end, over-extracted coffee has everything we want in the brew, but then also things that we don’t want. This undesirable flavoring material pollutes the finished brew. Coffees that are over-extracted (i.e., include more than 22% of available water-soluble compounds) generally taste harsh, bitter and drying (astringent).

If you’re super motivated and have some cash to spare, you could purchase some tools to help calculate the extraction percentage of your coffee. Or you can put your taste buds to use and practice drinking your coffee with some extra thought and consideration. Does your brew taste sour and devoid of sweetness? Is it harsh and bitter? You’re basically an expert taster at this point! But if you’ve read this far you’re ready to get to the final point – what do I dooooooo about any of this?

Making the Right Adjustments

Put simply, if you think you coffee is over-extracted, try making your grind coarser. This reduces the available surface area and allows less flavoring material to be extracted. Additionally, you can lower your brewing temperature, so long as you’re staying between 195-205 degrees. Hotter water extracts more readily than less-hot water. Similarly, if you suspect your coffee is under-extracted, just do the opposite! A finer grind will increase surface area and make it easier for flavoring material to be dissolved in your brew. And hotter water will increase the rate of extraction.