Why Does My Espresso Taste Sour And How To Dial In Your Grind

Sour espresso can be frustrating—especially when you've invested in quality beans and a capable machine. That sharp, acidic, almost vinegar-like flavor isn't just unpleasant; it's a signal that something has gone wrong in the extraction process. While many assume sourness means under-extraction, the root cause often lies deeper: an improperly dialed-in grind. Understanding the science behind extraction and mastering grind adjustment are essential steps toward pulling consistently delicious shots.

This guide breaks down the reasons behind sour espresso, explains how grind size affects flavor, and provides a practical, step-by-step method to dial in your grinder with precision. Whether you're using a home setup or refining your technique at a semi-pro level, these insights will help you achieve sweeter, more balanced espresso.

Understanding Sourness in Espresso

When espresso tastes sour, it typically indicates under-extraction. This occurs when water passes through the coffee grounds too quickly, extracting primarily the bright, acidic compounds while leaving behind the sugars and body-building elements that contribute to sweetness and complexity.

Coffee contains hundreds of soluble compounds, which extract at different rates:

• Acids (like malic, citric, and tartaric) extract early in the brewing process.
• Sugars and caramelized compounds emerge mid-way through extraction.
• Bitter notes and body components appear later, especially if extraction continues too long.

If your shot finishes too fast—say, under 20 seconds—you’re likely capturing only the first wave of solubles: acidity. Without sufficient contact time, the desirable sweetness and mouthfeel never make it into the cup. The result? A thin, sour, one-dimensional shot.

“Sour espresso is rarely about bad beans—it’s about bad timing. If your shot runs too fast, you’re not giving the water enough time to pull out the good stuff.” — Carlos Mendez, Head Roaster at Origin Coffee Lab

The Role of Grind Size in Extraction

Grind size is the most influential variable in espresso extraction. It controls how easily water flows through the puck and how much surface area is exposed for extraction. Even minor adjustments can dramatically shift flavor balance.

A coarse grind creates larger particles with less surface area relative to volume. Water moves through quickly, reducing contact time and leading to under-extraction. Conversely, a fine grind increases surface area and slows water flow, allowing for longer extraction and access to more complex flavors.

However, going too fine introduces its own problems: channeling, clogging, and over-extraction, which leads to bitterness. The goal is to find the sweet spot where water flows evenly and extraction is complete within an ideal time window.

Tip: Always change only one variable at a time when dialing in. Start with grind size before adjusting dose or yield.

Step-by-Step Guide to Dialing In Your Grind

Dialing in refers to the process of adjusting your grinder to achieve optimal extraction based on your equipment, beans, and environment. Follow this structured approach to eliminate guesswork and arrive at a balanced shot.

1. Weigh and dose consistently: Use a precision scale to dose between 18–20g of coffee, depending on your portafilter basket. Consistency here ensures reliable comparisons.
2. Set your target yield: Aim for a 1:2 ratio—for example, 18g in, 36g out. Adjust later based on taste, but start here as a baseline.
3. Set your shot time goal: Target 25–30 seconds from button press to drop. This includes pre-infusion if your machine uses it.
4. Pull your first shot: Record the time, weight, and visual flow. Note any spluttering, uneven streams, or fast dripping.
5. Taste and evaluate: Is it sour? Bitter? Thin? Harsh? Take notes. Sourness = likely too coarse. Bitterness or dryness = possibly too fine.
6. Adjust the grind incrementally: If sour, go finer by 1–2 clicks (or half-turn on stepped grinders). Wait 30 seconds for carryover grounds to clear, then pull again.
7. Repeat until balanced: Continue adjusting and tasting until you achieve a shot that’s sweet, full-bodied, and harmonious.

Patience is key. Rushing this process leads to confusion. Allow time between adjustments—especially with low-burrs or high-retention grinders—to avoid residual inconsistencies.

Common Pitfalls and How to Avoid Them

Even experienced baristas make mistakes during the dial-in process. Awareness of these common issues helps prevent frustration and wasted beans.

Issue	Root Cause	Solution
Shot pulls too fast (<20 sec)	Grind too coarse	Fine-tune grind setting; check for correct basket size
Uneven stream (one side faster)	Poor distribution or tamping	Use a distribution tool; apply even pressure when tamping
Channeling (sputtering, fast finish)	Inconsistent puck prep or fines migration	Improve tamp consistency; consider bottomless portafilter
Shot tastes sour despite long time	Low brew temperature or old beans	Verify machine temp; use fresher roast (7–21 days post-roast)
Flavor changes mid-day	Grinder heat buildup or humidity	Burr cool-down; adjust grind slightly as day progresses

Tip: Clean your grinder weekly. Old coffee oils degrade flavor and disrupt grind consistency, leading to erratic shots.

Real-World Example: Fixing Sour Shots at Home

Consider Sarah, a home barista using a popular entry-level espresso machine and a conical burr grinder. She consistently pulled 18g doses yielding 36g in 18 seconds. Her shots tasted sharply sour, with no sweetness or body.

After reading about extraction principles, she adjusted her grind finer by three clicks. The next shot took 24 seconds—still fast, but smoother. She went one click finer. The third shot ran for 27 seconds, produced a steady, honey-like stream, and tasted noticeably sweeter, with hints of chocolate and citrus.

She repeated the process the next morning after the grinder cooled overnight. This time, the same setting ran too slow (35 seconds), so she adjusted back half a click. With consistent dosing and tamping, she achieved repeatable, balanced shots—all by focusing on grind and timing.

Sarah’s experience shows that small, deliberate changes lead to big improvements. Equipment limitations don’t have to mean poor results—precision and observation do.

Essential Checklist for Successful Dial-In

Before each session, run through this checklist to ensure consistency and accuracy:

• ✅ Confirm dose (e.g., 18–20g) using a calibrated scale
• ✅ Check bean freshness (ideally 7–21 days post-roast)
• ✅ Clean portafilter and group head
• ✅ Purge grinder (run briefly to clear old grounds)
• ✅ Distribute coffee evenly (tap or use a leveling tool)
• ✅ Apply firm, level tamp (30–40 lbs of pressure)
• ✅ Pre-wet filter basket and wipe group head
• ✅ Pull shot and record time, weight, and taste notes
• ✅ Adjust grind and repeat if needed

Keeping a logbook—or even simple notes on your phone—helps track patterns across days and roasts. Over time, you’ll recognize how different beans respond to specific settings.

Environmental and Equipment Factors

It’s not just grind size that affects extraction. Several external factors influence how your espresso turns out:

• Humidity: High moisture in the air causes coffee to clump, disrupting grind uniformity. Store beans in an airtight container with a one-way valve.
• Bean age: Freshly roasted beans release CO₂, which can interfere with extraction. While degassing is necessary, extremely fresh beans (under 5 days) may produce uneven, bubbly shots.
• Water quality: Hard water scales machines and alters extraction. Use filtered water with balanced mineral content (ideal: 50–100 ppm total hardness).
• Machine stability: Fluctuating boiler temperatures lead to inconsistent results. Allow at least 20 minutes for your machine to stabilize before dialing in.

These variables explain why your perfect setting yesterday might not work today. True mastery comes from adapting—not just repeating.

FAQ: Common Questions About Sour Espresso

Can dark roasts taste sour?

Yes, even dark roasts can taste sour if under-extracted. While darker roasts tend to be less acidic, improper grind or short shot time prevents full extraction, leaving behind unbalanced acidity.

Should I increase my dose if my espresso is sour?

Not necessarily. Dose affects strength and resistance, but grind size controls extraction speed. Start with adjusting the grind. Only modify dose once grind, time, and yield are stable.

How do I know when my grind is “just right”?

Your ideal grind produces a shot that meets your time target (25–30 sec), yields your desired ratio (e.g., 1:2), and tastes balanced—sweet, aromatic, and layered, without harsh sourness or bitterness.

Final Thoughts and Next Steps

Sour espresso isn’t a dead end—it’s feedback. It tells you that your current setup isn’t extracting fully, and the most effective fix is usually a finer grind. But true excellence comes from understanding *why* and applying systematic adjustments.

Dialing in isn’t a one-time task. It’s a daily ritual shaped by bean freshness, ambient conditions, and equipment behavior. Treat it with care, document your results, and refine your palate over time.

🚀 Ready to transform your morning espresso? Grab your notebook, adjust your grinder in small steps, and taste the difference. Share your dial-in journey in the comments—what worked, what didn’t, and how your coffee improved.