Why Does My Coffee Taste Sour?

It's a question I get asked often. The good news is that sour coffee usually has a simple cause, and an easy first fix.

Sourness vs. acidity

First, it helps to be clear about what we mean by sour. All of our coffees have acidity, and that's a good thing. What we want is pleasing acidity: sweet and juicy, like biting into a fresh, ripe orange.

Sourness is different. Think of an unripe orange. It's sharp, astringent and not pleasant at all. If that's what you're tasting in your cup, something in the brew is off.

Why coffee tastes sour: under-extraction

When we brew coffee, we're extracting dissolvable solids, along with volatile aromatics, from the grounds into water. That's essentially what coffee is.

Sourness often comes from low extraction. The water isn't pulling enough of the available solids out of the coffee, so the flavours that come out first, the sharp and sour ones, aren't balanced by the sweetness that follows.

The fix: grind a little finer

The simplest starting point is your grind size. A finer grind allows for more extraction, which should bring that sourness down into a more pleasing, tasty acidity.

Try this on your next brew:

• Keep your coffee dose the same.
• Keep your amount of water the same.
• Grind just a little finer.
• Brew and taste.

As a reference point, I brew on a Moccamaster using 60 grams of coffee to one litre of water. Whatever ratio you use, keep it steady while you adjust the grind, so you know the grind is what made the difference.

This is the opposite of the fix for bitter coffee, where you'd grind coarser. Our Coffee Grinding Guide has more on finding the right setting.

Some coffees are just bright

Some coffees naturally have a very bright character. Our Ndiaini Peaberry from Kenya, for example, is very bright and juicy by its nature. No grind adjustment will change that.

If brightness isn't what you enjoy, look for coffees outside our yellow flavour category and try something from the browns or purples in our coffee lineup. But if you enjoy a bright coffee and it just tastes out of balance, start with your grinder and go a little finer.

Have a coffee question you'd like answered? Ask me. It could be the next video.

More short coffee answers from Coffee Made Simple →