Coffee tastes too sour
The cup tastes sharply sour or acidic rather than balanced, often alongside a thin body.
Applies to: Espresso machine, V60 (pour-over), AeroPress, Espresso, Filter coffee
Why coffee tastes sour
CoffeeHQ explanation
A cup that has given up too little of its coffee usually tastes sharp, thin and hollow. That is under-extraction, and as a rule of thumb about whole cups it is reliable enough to act on. The tidy story often told with it, that sharp-tasting compounds dissolve first and bitter ones last, did not hold up when drip coffee was collected in fractions as it brewed: the earliest liquid was rated more sour and more bitter than what came later. So treat sourness as a sign that more extraction is worth trying, not as proof of what has or has not dissolved.
Anything that makes extraction less effective can cause it: a grind that is too coarse, too short a contact time, cooler water, or water that never reached part of the coffee at all. Water temperature works here as one more way of moving extraction. In a controlled test, a trained panel found little difference between brews made a few degrees apart once strength and extraction were matched, so a kettle setting is not a cause in its own right.
Sourness is not the same as acidity. Many good coffees are deliberately bright, with a clean, juicy acidity like fruit. The difference is what comes with it: pleasant acidity arrives with sweetness, and sourness arrives with nothing.
Causes, most likely first
There are 3 likely causes, listed with the most probable first. Work down the list and change one thing at a time, so that when the problem goes away you know which change fixed it.
Cause 1 of 3 · Commonly the cause
Too little was taken from the coffee (often called under-extraction); a strong brew or a light roast can taste sharp too
- How to check
- Does the cup also taste thin, alongside the sourness?
- What to change
- Use a slightly finer grind, or increase contact/brew time.
Cause 2 of 3 · Reported, not independently verified
Water too cool
- How to check
- Did the water sit for a while after boiling, or come from a lower-temperature kettle setting?
- What to change
- Increase water temperature towards the typical range for the method.
Cause 3 of 3 · Reported, not independently verified
Coffee dose too low for the water volume
- How to check
- Have you measured your dose recently, or are you estimating it?
- What to change
- Increase the coffee-to-water ratio slightly.
If none of these fixes it
Check the cleaning and descaling guide. Equipment that needs maintenance can cause several of these symptoms at once, and no change of recipe will correct it.
Work through it for your setup
The causes above are general. These go to the part of a diagnostic that takes this symptom one check and one change at a time.
- Make my coffee betterChoose your brewer and tick what you noticed
- Dialling in filter coffee: the same symptom, different causes
- It foams hard, brews unevenly or tastes sharp, and the bag was roasted very recentlyThe possibilities, the quickest check and one thing to change first
How it shows up on different brewers
Tendency, not a guarantee
- Espresso
- A shot that gushes out in well under 25 seconds is the classic cause. Grind finer. If the time is already reasonable, let the shot run a little longer or raise the temperature.
- Pour-over
- Grind a step finer and use hotter water. Check that the bloom wets all the coffee: dry pockets do not extract.
- AeroPress
- Use hotter water first, since this brewer is often used well below boiling. Then extend the steep by half a minute.
- Cold brew
- Rarely sour. If it is, the steep was too short for the temperature; leave the next batch several hours longer.
When the brightness belongs to the coffee
A lightly roasted coffee is brighter to begin with, and no recipe turns it into a dark one. If a coffee stays sharp at every grind you try and the same recipe suits another bag, the roast is the likelier answer. Water is a smaller suspect than is often claimed: in the one controlled tasting CoffeeHQ has read, it was high alkalinity that muted acidity, and hard water was not told apart from very pure water.
Easily confused with
- Bitterness — People often say bitter when they mean sour, and the fixes are opposite. Sour is immediate and sharp and makes your mouth water; bitter comes later and lingers.
- Channelling in espresso — A shot that is sour and bitter at once has extracted unevenly. Grinding finer will not help and may make it worse; the puck preparation needs attention.
What not to change at the same time
Do not grind finer and raise the temperature in the same brew. Both increase extraction, and together they can carry you straight past balanced into bitter.
How to tell it is fixed
The sharpness should give way to sweetness and the cup should feel fuller. Some brightness will remain in a light roast and is meant to. Stop when it tastes like fruit and not like vinegar.
Understand the science: Coffee extraction — What under-extraction is, and why the order-of-dissolving story does not survive measurement.
Related issues
What to change
Specific adjustments for this symptom, with what each one trades off.
Work it out
Interactive tools that take you through this one change at a time.
Learn the technique
Step-by-step guides to the skills this problem comes from.
- Dialling in espressoFind the grind setting and recipe that make a particular coffee taste as intended, and be able to return to it.
- Adjusting grind sizeMove the grind in the right direction by a useful amount, and know what to expect from the change.
- Dialling in filter coffeeFind the grind and ratio that suit a particular coffee in a particular brewer, using brew time as a reading and never as a target.
- Blooming coffeeWet the whole coffee bed and let it release its carbon dioxide before the main pour begins.
- Preheating a brewerStop cold equipment taking heat out of the brew before it has finished extracting.
- Tasting coffee deliberatelyNotice what a coffee is actually doing, rather than only whether you like it.
- Measuring extraction yieldTurn a TDS reading into an extraction percentage, and know what that number can and cannot tell you.