Most common causes: grind size too coarse, brew time too short, water too cold, or very light roast. Solution: grind finer, brew longer, increase water to 94–96 °C. Pleasant fruit acidity is desired — piercing sourness is not.

Why does my coffee taste sour?

Most common causes: grind size too coarse, brew time too short, water too cold, or very light roast. Solution: grind finer, brew longer, increase water to 94–96 °C. Pleasant fruit acidity is desired — piercing sourness is not.

Why this is so

Sour coffee is the opposite of bitter coffee — and has the opposite cause: underextraction. Too little was dissolved from the coffee grounds.

How this works:

Aroma compounds dissolve in a fixed order: First fruit acids (sour, tangy). Then sugars and caramel (sweet, round). Finally bitter compounds (bitter, harsh). With underextraction, only the first group gets into the water — the coffee tastes one-dimensionally sour, thin, and unripe.

Cause and solution by brewing method:

Method	Typical Cause	Solution
Filter coffee / Pour-Over	Grind too coarse, poured too fast	Grind finer, pour slower
French Press	Steeping time too short (under 3.5 min)	Let steep for 4 minutes
Espresso	Grind too coarse, shot too short	Grind finer, 25–30 s brew time
AeroPress	Contact time too short	Increase steeping time to 1.5–2 min

Other causes:

• Water too cold: Below 90 °C, the water dissolves the acids, but hardly any of the sweet and round aromas. Ideal temperature: 92–96 °C. Waiting 30 seconds right after boiling is often too long — it’s better to work with a thermometer.
• Very light roast: Light roasts emphasize natural fruit acids. This is intentional and common with specialty coffee. But not everyone likes it. If light roasts are fundamentally too sour for you, try a medium roast.
• Fresh beans (too fresh): Coffee needs 5–10 days after roasting to degas. Beans that are too fresh (under 5 days) can taste unbalanced and sour.

Important: Not all acidity is created equal. Pleasant fruit acidity (bright, lively, like a good apple) is a quality feature of specialty coffee. Piercing, vinegar-like sourness is a flaw. The difference: fruit acidity is pleasant and disappears quickly, flawed sourness lingers unpleasantly in the mouth.

In practice at Green Wall Coffee

At Sophienstraße 27, we often experience guests confusing pleasant fruit acidity with “sour” — especially if they have only known dark-roasted coffee up to now. We then have them try different roast levels side-by-side. Anyone who genuinely has coffee at home that is too sour gets the tip from us: first grind finer, then check the water temperature.

Related questions

• Why does my coffee taste bitter?
• What is underextraction and overextraction?
• Why does my espresso taste sour?

You can find more depth on this topic in the article How to make perfect espresso. Or drop by Sophienstraße 27 — Mon–Fri 8am–5pm, Sat 10am–5pm.