Why Is My Espresso Sour? The Ultimate Fix Guide

You did everything right. You weighed your beans, distributed the grounds, tamped perfectly, and watched a beautiful stream of espresso pour into your cup. You take an eager sip and... bam.

Your face puckers. It tastes like hot lemon juice.

If this sounds familiar, you're not alone. Sour espresso is the most common frustration for home baristas, especially those just starting out or experimenting with specialty coffee. But don't throw those beans away just yet.

Here is exactly why your espresso tastes sour—and the three fastest ways to fix it.

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Why Is It Sour? The Science of Under-Extraction

When water interacts with coffee grounds, it dissolves compounds in a specific order:

1. Fruity, acidic flavors (sourness) extract first.
2. Sweet, complex flavors extract second.
3. Bitter, roasty flavors extract last.

If your espresso tastes overwhelmingly sour, you stopped the extraction process too early. Your water didn't have enough time, heat, or surface area to reach the sweet and bitter compounds that balance out those initial acidic flavors.

In the coffee world, we call this under-extraction.

Are you sure it's sour, not bitter?

Wait, what? Yes, our brains often confuse extreme sourness and extreme bitterness.

• Sourness makes the sides of your tongue water and causes an involuntary pucker (like biting a lemon).
• Bitterness dries out the back of your tongue and lingers unpleasantly (like chewing an aspirin).

If you're definitely dealing with a lemon-like sourness, keep reading.

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The 3-Step Fix for Sour Espresso

When fixing an espresso issue, only change one variable at a time. If you change your grind size and your temperature at the same time, you won't know which one actually fixed the problem.

Try these fixes in order:

Fix 1: Pull a Longer Shot (Increase Yield)

The easiest and most effective fix. If the sweet and bitter compounds extract after the sour ones, the simplest solution is to just keep the water running a little longer.

• If you currently pull: 18 grams in, 36 grams out (a 1:2 ratio)
• Try pulling: 18 grams in, 45 grams out (a 1:2.5 ratio)

Yes, the shot will run for a few seconds longer. Yes, it will be slightly less viscous. But the extra water will pull out the sweetness needed to balance the aggressive acidity.

Fix 2: Grind Finer (Increase Contact Time)

If you pulled a longer shot and it still tastes sour (or if the shot ran incredibly fast—like 15 seconds), your water is finding it too easy to rush through the coffee puck.

By grinding finer, you increase the surface area of the coffee and create more resistance. The water has to work harder and longer to push through, extracting more sweetness along the way.

• The Goal: Aim for your shot to take around 25-30 seconds. If it's finishing in 15-20 seconds, grind finer.

Fix 3: Turn Up the Heat

Coffee compounds need heat to dissolve. If your water is too cold, it will struggle to extract the sweet compounds in time, leaving you with—you guessed it—sour espresso.

• The Fix: If your machine has a PID (temperature controller), increase the temperature by 1°C or 2°F (e.g., from 93°C to 94°C).
• Note on Light Roasts: Lightly roasted, dense specialty beans are notoriously hard to extract and almost always require higher temperatures (94°C-96°C) to avoid tasting sour.

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