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

If your morning espresso tastes sharp, tangy, or unpleasantly acidic—especially with a lack of sweetness or body—you're likely dealing with under-extraction. Sourness in espresso is one of the most common complaints among home baristas and even professionals during machine transitions or bean changes. The good news? It’s usually fixable with precise adjustments to your grind size, dose, and technique.

Espresso extraction is a delicate balance between water, time, pressure, temperature, and particle size. When any of these variables are off, the result can be a sour shot that lacks depth and complexity. Understanding the science behind extraction—and how to systematically adjust your setup—can transform your daily espresso from disappointing to exceptional.

What Causes Sour Espresso?

Sourness in espresso is typically a sign of under-extraction. This means the water passed through the coffee puck too quickly, pulling out primarily the acidic, volatile compounds present in the first stages of extraction while leaving behind the sugars, chocolates, and deeper flavor notes that emerge later.

Under-extracted espresso often presents with:

• A bright, vinegary acidity that overwhelms the palate
• Lack of sweetness or body
• Short finish or abrupt aftertaste
• Thin mouthfeel, almost like weak tea

The root cause lies in the contact time between water and coffee grounds. If the grind is too coarse, water flows too fast through the puck. Even with correct dose and tamping, a coarse grind reduces surface area exposure, limiting the extraction of desirable compounds.

“Sour espresso isn’t necessarily bad beans—it’s usually bad timing. You’re stopping the extraction before the good flavors have a chance to come out.” — Luca Moretti, Head Roaster at Verve Coffee Roasters

How Grind Size Affects Extraction

Grind size is the single most influential variable in dialing in espresso. Unlike drip coffee, where small inconsistencies are buffered by longer brew times, espresso operates on a 25–30 second window. A fraction of a millimeter difference in particle size can shift extraction from balanced to sour—or worse, to bitter.

When your espresso tastes sour, your first adjustment should almost always be to go finer on the grind. Finer particles increase surface area and slow down water flow, allowing more time for extraction. But it’s not just about making the grind finer—it’s about doing so methodically.

Tip: Make micro-adjustments—one notch at a time on your grinder—and wait for the next dose to stabilize. Rushing changes leads to confusion.

Blade grinders are especially problematic because they produce inconsistent particle sizes. For serious espresso work, a burr grinder—preferably flat or conical burr—is essential. Inconsistent grinds lead to both over- and under-extraction in the same shot, muddying flavor clarity.

The Role of Dose in Extraction Consistency

Dose refers to the amount of dry coffee you use per shot, typically measured in grams. While dose doesn’t directly cause sourness, an incorrect dose can amplify issues caused by grind size or basket fit.

Too little coffee (e.g., 16g in a 20g basket) creates a shallow puck, increasing channeling—where water finds paths of least resistance and bypasses much of the coffee. This speeds up flow and contributes to sourness.

Too much coffee (e.g., 22g in a 18g basket) causes over-packing, leading to restricted flow, over-extraction, and bitterness. Neither extreme helps achieve balance.

The ideal dose fills the portafilter basket 70–80% full when evenly distributed and tamped. Most standard double baskets hold 18–20g. Match your dose to your basket’s capacity for optimal puck formation.

Dialing In Your Espresso: A Step-by-Step Guide

Dialing in espresso is the process of adjusting variables until you achieve a balanced, sweet, and complex shot. Follow this structured approach to eliminate sourness and find your sweet spot.

1. Start with fresh beans: Use coffee roasted within the past 2–4 weeks. Stale beans lose CO₂ and solubles, making even perfect technique yield flat or sour results.
2. Weigh your dose: Begin with a dose that matches your basket (e.g., 18g for an 18g basket). Use a precision scale (0.1g accuracy).
3. Set grind to medium-fine: Start near the factory setting if using a new grinder. Aim for table salt consistency.
4. Pull a test shot: Target a 1:2 ratio (e.g., 18g in → 36g out). Time the shot from pump start to desired weight.
5. Evaluate taste and time:
   • If shot finishes in under 25 seconds and tastes sour → grind finer.
   • If shot takes over 35 seconds and tastes bitter → grind coarser.
6. Adjust one variable at a time: Only change grind size initially. Wait 2–3 shots after each adjustment to allow the grinder to stabilize.
7. Refine distribution and tamp: Once flow rate improves, ensure even distribution (using a tool like a WDT or gentle stir) and consistent tamping pressure (~15 kg).
8. Repeat until balanced: Aim for a shot that tastes sweet, slightly acidic (like citrus), with chocolate, nutty, or caramel notes—not harsh or thin.

Real Example: Fixing Sour Shots at Home

Mark, a home barista in Portland, bought a new semi-automatic machine and started pulling sour shots every morning. He was using a popular light-roast Ethiopian bean and a mid-range conical burr grinder. His initial setup: 17g dose, 32g output, 22-second shot time.

Despite adjusting his tamp and trying different water temperatures, the sourness persisted. After logging his shots, he realized his grinder was set too coarse. He adjusted one notch finer and increased his dose to 18.5g to fill his larger basket properly. The next shot took 28 seconds and yielded a syrupy, jasmine-scented espresso with balanced acidity and honey-like sweetness.

The fix wasn’t a new machine or beans—it was patience, measurement, and understanding that extraction begins with grind and dose alignment.

Common Mistakes That Lead to Sour Espresso

Even with the right equipment, small errors can sabotage your shot. Avoid these frequent pitfalls:

Mistake	Why It Causes Sourness	Solution
Grinding too coarse	Water flows too fast, extracting only acids	Adjust grinder finer in small increments
Inconsistent dose	Uneven puck density affects flow	Use a scale; match dose to basket size
Poor distribution	Channels form, causing uneven extraction	Use a WDT tool or gentle stir before tamping
Low brew temperature	Reduced solubility of sugars and oils	Ensure machine reaches 92–96°C (198–205°F)
Stale or poorly stored beans	Loss of CO₂ and aromatic compounds	Store beans in an airtight container away from light

Tip: Always purge your group head before pulling a shot to stabilize temperature and clear old residue.

Optimal Brew Ratios and Targets

Brew ratio—the relationship between input (dose) and output (yield)—plays a key role in flavor development. While personal preference matters, here are industry-recommended starting points:

• Standard ratio: 1:2 (e.g., 18g in → 36g out)
• Concentrated (ristretto): 1:1.5 (sweeter, denser, less acidic)
• Longer (lungo): 1:2.5 to 1:3 (higher extraction, risk of bitterness)

For sour shots, try shifting toward a ristretto-style ratio. Less water passing through the puck reduces the chance of under-extraction while emphasizing sweetness. For example, pulling 27g instead of 36g from an 18g dose may reveal hidden chocolate and fruit notes previously masked by sourness.

“The best espresso tells a story. If it’s all sour, you’ve only heard the first sentence.” — James Hoffmann, World Barista Champion

Essential Checklist: Dial-In Routine for Balanced Espresso

Follow this checklist every time you switch beans or notice flavor changes:

• ☑ Use freshly roasted, properly stored beans (within 4 weeks of roast date)
• ☑ Weigh your dose with a 0.1g precision scale
• ☑ Match dose to basket capacity (e.g., 18g dose in 18g basket)
• ☑ Grind fresh immediately before brewing
• ☑ Distribute grounds evenly (WDT or fingertip stir)
• ☑ Tamp with consistent pressure and level surface
• ☑ Set target yield (start with 1:2 ratio)
• ☑ Time the shot from pump engagement to target weight
• ☑ Taste critically: look for sweetness, balance, and aftertaste
• ☑ Adjust grind finer if sour and under 25 seconds; coarser if bitter and over 35 seconds

Frequently Asked Questions

Can dark roasts also taste sour?

Yes, though less commonly. Even dark roasts can taste sour if severely under-extracted. Over-roasted beans may develop acrid, burnt notes, but true sourness still points to insufficient extraction time or overly coarse grind.

Should I change my dose or grind first?

Always adjust grind first. Dose affects shot volume and concentration, but grind size controls flow rate—the primary factor in extraction balance. Only tweak dose after stabilizing your grind setting.

How do I know when my espresso is “balanced”?

A balanced shot has harmony between acidity, sweetness, and bitterness. It should feel full-bodied, finish cleanly, and express the inherent qualities of the bean—floral, fruity, chocolatey, etc.—without any single note dominating unpleasantly.

Final Thoughts: Mastering the Daily Ritual

Fixing sour espresso isn’t about perfection on the first try—it’s about developing a repeatable, mindful process. The machine doesn’t make great coffee; the barista does. With attention to grind, dose, and timing, you can consistently pull shots that are rich, nuanced, and deeply satisfying.

Every bean, every day, reacts differently. Humidity, roast age, and even water quality influence the outcome. Embrace the ritual of dialing in as part of the joy of espresso—not a chore, but a craft.

💬 Start today: Pull a shot, taste it honestly, and make one small adjustment. Repeat tomorrow. Within a week, your espresso will taste like it belongs in a specialty café.