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Why Does My Coffee Taste Sour?
(With Reliable, Easy Fixes)

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By Matt Woodburn-Simmonds

Drinking coffee should be a daily infusion of happiness. The comforting warmth and rich flavors make everything feel better. But drinking a sour coffee is a sure way to ruin your day. If your coffee tastes sour regularly, it could put you off drinking this beautiful elixir entirely.

The simple answer to ‘why does my coffee taste sour’ is under-extraction. The reason for a sour coffee issue is that different flavors are extracted from coffee grounds at different rates. And the sour, acidic notes come first. So, if the extraction stops too quickly, you won’t get the sweet notes to balance the sour ones.

Thankfully, there are easy ways to fix this sour coffee problem. Here, we’ll walk you through the simple steps to better-tasting coffee:

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Under-Extracted Coffee

Sour coffee is usually under-extracted coffee.

The flavor is extracted from your coffee grounds in stages:

  1. The acidic notes come first
  2. Then the sweet, aromatic notes
  3. Finally, the bitter flavors at the end

Getting the perfect extraction – and a delicious-tasting cup of joe – means getting a balance of all these flavors. But, if the extraction is stopped at the first stage (under-extraction), you don’t get any of the sweet and bitter flavors, just a cup full of sourness.

Under-extraction can be caused by a number of different things and it might take a little trial and error to work out the problem in your particular case. But we will break down all the main reasons and their fixes:

Infographic: Main causes of sour tasting coffee
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Main Causes of Sour Coffee and How to Fix Them

1. Bad Coffee Beans = Sour Coffee

It doesn’t matter if you do everything else right, if you use bad coffee beans you can end up with sour coffee.

If your coffee beans are under roasted then they’ll taste sour, grassy, and “green”. While many coffee roasts aim to show off the more citric flavors, this is a very different flavor profile to unpleasant sour coffee.

If you have stale coffee beans, they can also taste sour. Over time, coffee beans lose the aromatic oils that give them much of their delicious coffee flavor. So if your beans have been sitting around for a long time then they may have lost all this flavor. The result will be sour or bitter flavors in your cup.

The Fix

To avoid leaving a nasty taste in your mouth, opt for ultra-fresh coffee beans from a quality roaster.

2. Grinding too Coarse

The larger the individual grounds, the longer it takes to extract the flavor from them. If you want to get technical, this is due to the surface area to volume ratio of the grounds. But it basically means that you need more water in contact with the coffee grounds.

The Fix

Use a finer grind size.

The smaller your coffee grounds are, the more water they have in contact with them and the quicker the flavor compounds can be extracted. This means you should get a more balanced cup with all the sweet notes and a touch of bitterness.

3. Brew Time Was Too Short

When it comes to under-extraction, impatience and not brewing for long enough is possibly the most obvious issue.

If the water is in contact with the coffee grounds for too little time it’ll only extract the sour flavors. But, by extending the brewing time, the result will be a better-balanced cup of coffee.

The Fix

This will vary depending on your chosen type of coffee maker.

For pour over or espresso, you can extend the brewing time by grinding finer. The smaller grind size will cause the water to take longer to make its way through the grounds, meaning you get all the great flavors in your final brew.

It should take 20-30 seconds to brew espresso and around 4 minutes for pour over.

If you’re using a French press, the perfect coffee brewing method is to allow your coarse ground coffee to steep for 4 minutes.

4. Water Isn’t Hot Enough

Brewing coffee is a chemical reaction. And like all chemical reactions, they happen faster when you add more energy (cue traumatic science class flashbacks).

But if your water isn’t hot enough and you use the correct brewing time for your brewing method, the result will likely be sour coffee (or it could make your coffee taste watery instead). The right amount of energy (heat) is needed in order to extract all the flavors in the set brewing time.

The Fix

Ensure your water is between 195-205°F, most baristas (including us!) agree on a sweet spot of 200°F (93°C). But be careful not to go above this or you’ll end up with burnt-tasting coffee.

You can do this with a temperature-controlled kettle or by playing with the settings on your espresso machine. If your espresso machine doesn’t have temperature settings then use a meat thermometer to test the water temperature and fix sour coffee.

5. Not Enough Water

Even if you’re nailing everything else, there needs to be enough water for all those delicious flavors to go into. Too little water will result in sour coffee.

This is literally the point of the Ristretto (short espresso variation). But if you’re not aiming for that, then you’ll get a sour-tasting coffee.

The Fix

Up the amount of water you’re using. Coffee, like any recipe, needs the right balance and quantity of ingredients. Luckily, it only has two ingredients – coffee and water – so it makes the calculations a little easier.

If you’re using a French press, you can use our simple French press ratio calculator. Or, we have one to nail your Hario V60 recipe or a Chemex ratio calculator. Each will give provide done-for-you quantities to make sure you have enough coffee grounds and water for the perfect balance.

For espresso, you should be aiming to get twice the weight of brewed espresso out to ground coffee in. So, to get a 2oz shot of espresso, you need 1oz of coffee grounds. We recommend using a coffee scale to check your espresso ratio.

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Sour vs Acidic: What’s the Difference?

Acidity is a necessary component of coffee to get the best flavor.

Acidic vs Sour Coffee

Your coffee bean blend may have used acidic beans along with more mellow ones and also rich flavored beans to give a balanced cup. Or a light roast coffee may have been roasted with acidic, citrusy notes in mind.

Acidity should be pleasant though, not sour. It should bring up images of fresh fruit like apples, berries, and citrus. Many specialty coffee beans have these bright refreshing fruity coffee flavors balanced with sweeter, chocolatey notes.

If you get the impression of fresh fruit and a pleasant mouth-watering sensation, you have good acidity. But, if you instantly screw your face up like you’ve just sucked on a lemon, then it’s sour.

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Final Thoughts

Sour tasting coffee is very unpleasant. So, the first step to fixing it is to make sure you’re using correctly roasted, fresh, top-quality coffee beans. From there, all the other issues are incredibly easy to fix.

Remember to try each of these fixes one at a time rather than all at once. In no time, you’ll go from wondering ‘why does my coffee taste sour’ to ‘how many extra cups can I sneak into my day?’


Matt Woodburn-Simmonds

Matt's coffee obsession started in 2006 when working as a Barista. A tendency to turn up to work hungover kickstarted his coffee journey which quickly turned into a love affair. As he moved on to work as a Restaurant Manager and Sommelier, the obsession continued to grow. Now, his passion is helping others to enjoy better coffee at home.

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