Why is my coffee too acidic?

When you experience a sharp, unpleasant sourness in your cup, you are likely dealing with under-extraction. In the world of coffee flavor, acidity is a prized, positive attribute—often described as bright, citrusy, or wine-like—that provides structure and vibrancy. However, when that acidity is not balanced by the sweetness and body that develop later in the extraction process, it manifests as a harsh, one-dimensional sourness that can make your mouth pucker.

Extraction is the process of dissolving soluble compounds from your coffee grounds into water. This happens in a specific sequence: acids and fruit-like notes dissolve first, followed by sugars and caramels, and finally, the heavier, bitter compounds. If your brew stops too early, you are left with only the initial acidic phase, missing the sugars that would have rounded out the flavor. This is why under-extracted coffee often feels thin or watery in addition to being sour.

Several variables can cause this. A grind size that is too coarse allows water to pass through the grounds too quickly, preventing adequate contact time. Similarly, water that is too cool lacks the thermal energy required to efficiently pull out the sugars and oils. Even your brew ratio matters; if you use too much water relative to the amount of coffee, you may dilute the brew to the point where the acidity dominates the profile.

To troubleshoot, adjust one variable at a time. If your coffee is sour, try grinding your beans slightly finer to increase surface area and resistance. If that doesn't work, ensure your water temperature is between 195°F and 205°F (90°C–96°C). You might also consider extending your brew time or slightly increasing your coffee-to-water ratio. By systematically adjusting these factors, you can move from a sour, unbalanced cup to one that highlights the complex, integrated acidity that specialty coffee is known for.

In practice, remember that some coffees are naturally more acidic due to their origin or light roast profile. While you should aim for balance, don't mistake a coffee's inherent, pleasant brightness for a brewing error. If the coffee tastes like fresh fruit, it is likely a high-quality, well-extracted cup; if it tastes like lemon juice or vinegar, it is time to adjust your brewing parameters.