Why Your Coffee Tastes Sour (and How to Fix It)

A bright, pleasant acidity (like biting into a crisp apple) is a highly desirable trait in specialty coffee. But when that acidity turns into a harsh, lip-puckering sourness (like biting into a lemon rind), something has gone wrong.

Sour coffee is a sign of under-extraction. The water didn't pull enough soluble compounds out of the coffee grounds. Because sour, acidic compounds are extracted first, and sweet compounds are extracted later, stopping the brew too early leaves you with only the sour notes.

Here is how to push the extraction further to find the sweetness.

1. Grind Finer

If the water flows through the coffee grounds too quickly, it won't have time to extract the sweet and bitter compounds.

Solution: Adjust your grinder to a finer setting. This increases the surface area of the coffee and slows down the water flow, increasing contact time and extraction.

2. Increase Water Temperature

Cooler water extracts flavors much slower. If your water isn't hot enough, it will struggle to break down the sugars in the coffee.

Solution: Use water right off the boil (around 96°C to 98°C). This is especially critical for light roast coffees, which are very dense and stubbornly resist extraction.

3. Lengthen the Brew Time

If you don't steep your French press long enough, or if your espresso shot gushes out in 15 seconds, it will be sour.

Solution:

• Immersion: Let it steep for an extra 60-90 seconds.
• Pour-over: Pour slower, or agitate (stir) the coffee slurry to increase extraction.
• Espresso: Pull a longer yield. Instead of a 1:2 ratio (18g in, 36g out), pull a 1:2.5 ratio (18g in, 45g out) to extract more sweetness.

4. Decrease Your Dose (Use Less Coffee)

If you pack too much coffee into your dripper for a small amount of water, the water won't be able to adequately extract all of those grounds.

Solution: Try opening up your ratio. If you are brewing at 1:14, try 1:16 to give the water a better chance to do its job.