Key Takeaways:

The main cause of sour espresso is under-extraction: when a shot extracts too fast (under 25 seconds) or hits a low temperature, failing to dissolve properly.
To fix sour coffee, grind finer or increase the final shot volume (yield) to ensure the shot time approaches the optimal 25–30 second range.
Advanced troubleshooting for sourness or bitterness requires adjusting the dose and tamping pressure, as mistakes here can cause problems even if the grind is correct.

Espresso is meant to be balanced, juicy, and delicious. But if your shots are hitting you with a sharp, unpleasant acidity, you're probably left wondering, “Why is my espresso sour?” Fortunately, diagnosing and fixing a defective shot is a precise science. This guide shares the complete, barista-approved strategy to fix sour espresso and perfect your home brewing.

Understanding Your Shot: Under-Extraction vs. Over-Extraction

Before you can fix the problem, you need to know the cause. Flavour defects in espresso almost always stem from one of two issues:

Under-Extraction (Sourness): This is the cause of sour espresso and happens when insufficient flavour compounds (like sweetness and body) are dissolved from the grounds. The result is a sharp, tart, sour espresso shot.
Over-Extraction (Bitterness): Too many unwanted, bitter compounds are dissolved. The result is a strong, heavy, or sometimes burnt flavour.

Why Is My Espresso Sour? The Telltale Signs of Under-Extraction

If you're tasting a sharp, lemon-like tartness, the classic sour coffee defect is present. The shot is sour because the water didn't spend enough time in contact with the coffee grounds, or the temperature was too low.

Here are the signs that your espresso is sour due to under-extraction:

The Flavour: A pronounced, unpleasant acidity. When espresso is too sour, the taste is often described as lemony or green apple-like.
The Flow: The shot extracts too fast (often under 25 seconds) and looks pale yellow, or 'blond,' very early in the shot.
The Puck: The spent coffee grounds in your basket may appear thin, wet, or sloppy, which is often a sign of under-dosing (too little coffee for the basket size).

3 Ways to Fix Your Sour Coffee

If you've realised your sour espresso is due to under-extraction, follow these simple steps to find the solution.

Fix #1 (The Standard): Adjust the Grind

The most common reason for a sour espresso shot is grinding too coarse. Grind finer to increase the resistance in the coffee bed. This will slow down the flow and increase the contact time, pulling more desirable flavours from the coffee.

Fix #2 (The Easiest): Adjust the Yield

An immediate solution without touching your grinder is to pull a longer shot. Increase the final liquid volume (yield). By allowing the water to extract for a couple of extra seconds, you increase overall extraction and reduce the chance that your shot is sour.

Fix #3 (The Advanced): Adjust the Dose, Tamp & Temperature

If your grind is fine but the shot is sour, you may be under-dosing. Increase the dose (amount of coffee) to increase resistance. Also, if your machine allows, increase the brew temperature, as low heat is a common reason why extraction fails.

Diagnosing Other Defects: Bitter and Burnt Flavours

For comprehensive espresso troubleshooting, it's important to identify other common issues.

Bitter Flavour: If your shot is slow (over 35 seconds) and tastes overly strong and heavy, you are over-extracting. Grind coarser to speed up the flow.
Channelling: If the taste is uneven (partially sour, partially bitter, and watery), it's likely due to channelling. This is when water finds a crack in the puck, usually due to uneven tamping or poor distribution.
Burnt Flavour: Does your espresso taste burnt? The issue usually points to excessively high water temperature or poor machine hygiene. If the espresso tastes burnt, check your machine's temperature settings and perform a thorough cleaning and backflush.

Your Handy Espresso Troubleshooting Guide

Make this table your secret weapon! It links all the common shot issues right back to what caused them. It's basically a cheat sheet for mastering your espresso extraction.

Symptom	Taste	Extraction Time	Primary Cause	Secondary Causes	Solution
Too Fast	Sour	<25 seconds	Under-extraction (Grind too Coarse)	Insufficient dose, low tamping pressure, machine temp too low	Grind finer / Increase dosage / Tamp harder
Too Slow	Bitter	>35 seconds	Over-extraction (Grind too Fine)	Excessive dose, uneven tamping, channeling	Grind coarser / Decrease dose / Tamp evenly
Fast and Watery	Sour and thin	<20 seconds	Machine running cold or Channeling	Improper puck prep, machine malfunction	Warm up machine properly, fix distribution
Slow and Intense	Overly bitter or burnt	Very slow or no flow	Grind too fine or Puck too Dense	Blocked shower screen or grouphead	Clean machine and baskets, adjust grind coarser
Sloppy Puck	Weak / weak crema	N/A	Low dose, coffee swells improperly	Basket size mismatch, uneven tamp	Increase dose, ensure correct basket, tamp level
Channeling	Uneven, watery taste	Variable	Uneven tamp or distribution	Wet basket, puck cracks	Even distribution & tamp, dry basket before use

Perfect Espresso Starts with Di Stefano

Fixing a sour espresso shot can actually be a rewarding process. You get to learn more about your equipment and how to make small, iterative adjustments to your grind, dose, and time. By mastering these variables, you’ll eliminate the defects and pull a perfect shot every time.

Ensure your next espresso starts with the best possible foundation: high-quality, freshly roasted beans. Shop the Di Stefano collection of speciality espresso beans and level up your home brewing today!

Frequently Asked Questions

Is it okay to drink sour espresso?

While it's not a health risk, sour espresso is a technical flaw indicating under-extraction. The shot only contains sharp, undesirable acids and is missing the rich sweetness and body. It means you’re missing the true flavour notes of your beans, which in our opinion is unacceptable!

What to do if espresso is too sour?

If your espresso is too sour, immediately increase the overall extraction. First, pull a longer shot (higher yield) without changing the grind. If that fails, adjust your grinder finer to increase flow resistance, ensuring the extraction time approaches the optimal 25–30 seconds.

How do you fix espresso that is too acidic?

Fixing acidic or sour coffee requires increasing resistance to slow the flow. Grind finer and confirm your dose is correct and your tamp is level. Also, check your machine's temperature, as low heat prevents proper dissolution, resulting in an overly sharp and sour taste.

Can grinding too fine cause sour espresso?

No, grinding too fine is the opposite problem. It causes over-extraction by slowing the flow excessively (over 35 seconds), resulting in a bitter flavour. Sour espresso is caused by the grind being too coarse, allowing water to rush through in under 25 seconds.

Additional Reading

Keen to learn more about brewing and making coffee? We have a stack of additional content to keep you informed.

---

About the Author

Nicolas Di Stefano, a third-generation Master Roaster and Director of Di Stefano Coffee, continues his family’s proud legacy of exceptional coffee craftsmanship. Blending traditional Italian roasting methods with a modern dedication to quality, Nicolas ensures every cup embodies the rich flavour and consistency Australians have come to love.