Coffee that tastes sour is often under-extracted, and coffee that tastes bitter and harsh is often over-extracted. If it is sour, grind a little finer or let the water touch the grounds longer; if it is bitter, grind a little coarser or shorten the time. Change only one thing at a time so you know what changed the taste.
Why does coffee taste sour or bitter?
The compounds in coffee grounds do not dissolve all at once; they come out in order. The Wikipedia article “Coffee extraction” explains that acids come out first and bitter compounds come later, after most acids and sugars have dissolved. So stopping early leaves sourness in front, and running too long puts bitterness in front.
The same article says an extraction yield (the share of the grounds that dissolves into the cup) of 18% to 22% is desirable for most traditional coffee beverages. Below 18% the cup is often unbalanced and sour; above 22% it is often bitter. This is a tendency, not a hard rule, and at home you cannot measure yield easily, so use taste as your guide.
What raises or lowers extraction?
The same source says smaller grains have more surface area and extract faster, and a longer brew time gives a higher yield. For typical coffee beverages it suggests water at 91-94 degrees C. That gives you three dials:
- Grind: finer extracts more, coarser extracts less.
- Time: the longer the water touches the grounds, the more is extracted.
- Temperature: hotter water dissolves more (91-94 degrees C is the reference range).
The order for fixing sour or bitter cups
Keep the coffee-to-water ratio fixed first. Changing it also changes strength and hides the cause. For the ratio itself, see the hand drip ratio guide.
FAQ
Can old beans also taste sour?
Bean condition does affect taste, but one brew cannot tell you whether storage or extraction is the cause. Change the brewing settings first; if nothing changes, check how you store the beans (see the bean storage guide).
Is sourness always bad?
No. Many coffees are prized for a bright acidity. The problem here is a sharp, unripe-tasting sourness with no sweetness.
If it is too bitter, can I just add water?
Adding water only dilutes it; the over-extraction behind the bitterness may remain. Grinding coarser or shortening the brew time comes first.
At Soruru Cafe
Soruru Cafe brews its hand drip coffee slowly, one drop at a time, from beans roasted every morning - see the menu. If you get stuck dialing in at home, visit us in Mangu - see getting here - and use a cup as your reference. The wooden space is a calm place to compare.
References
- Wikipedia, “Coffee extraction”: 18-22% extraction yield, extraction order of acids and bitter compounds, effect of grind, time and temperature (accessed 2026-11-07) - en.wikipedia.org