What causes coffee to taste bitter?
Bitterness in coffee is primarily caused by over-extraction, where too many soluble compounds—including those that are inherently bitter—are pulled from the grounds. This often happens when the grind is too fine, the water temperature is too high, or the contact time between water and coffee is too long, resulting in an unbalanced, harsh flavor profile.
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Bitterness is a natural component of coffee, but when it dominates the cup, it is usually a sign that the brewing process has gone too far. In brewing science, extraction is the process of dissolving flavor compounds from the coffee grounds into the water. While we want to extract sugars, acids, and aromatic oils, we must balance these against the extraction of bitter compounds, which are typically the last to be dissolved.
Over-extraction occurs when the water spends too much time in contact with the grounds or when the surface area of the coffee is too high, making it easier for the water to pull out those undesirable bitter elements. Common culprits include a grind size that is too fine for the chosen method, which increases the rate of extraction, or using water that is too hot, which accelerates the dissolution of bitter-tasting plant fibers and tannins.
It is important to distinguish between 'bitter' and 'burnt.' A dark roast may have inherent bitterness due to the roasting process itself, but if a light or medium roast tastes bitter, it is almost certainly an extraction issue. If your coffee tastes harsh, dry, or leaves a lingering unpleasant aftertaste, you are likely pulling too much out of the bean. Conversely, if the coffee tastes sour or thin, you may be under-extracting, meaning you haven't pulled enough of the balanced, sweet compounds to counteract the natural acidity.
In practice, fixing bitterness is a matter of adjusting your variables. If your coffee is consistently bitter, try coarsening your grind size slightly or reducing your total brew time. If you are using a pour-over, you might also try lowering your water temperature by a few degrees. By making small, incremental changes, you can find the 'sweet spot' where the coffee's natural sweetness and acidity are perfectly balanced, leaving the harsh bitterness behind.
- ·https://clivecoffee.com/blogs/learn/the-science-of-brewing-coffeeVerify source for reference 1 ↗