Why Does My Coffee Taste Sour And How To Adjust My Brewing Method

Coffee should be rich, aromatic, and balanced—not sharp or unpleasantly acidic. Yet many home brewers find themselves puzzled by a sour taste in their morning cup. This tangy, underdeveloped flavor isn't just off-putting; it's often a sign that something in the brewing process has gone awry. The good news is that sourness is usually fixable with small, intentional changes to your technique.

Sourness in coffee typically stems from under-extraction—when water hasn’t pulled enough flavor compounds from the grounds. But understanding *why* this happens requires looking at variables like grind size, water temperature, brew time, and bean freshness. By adjusting these elements thoughtfully, you can transform a tart, one-dimensional cup into a smooth, complex experience.

Understanding Coffee Extraction and Sourness

Extraction is the process of dissolving soluble compounds from ground coffee into water. These compounds include acids, sugars, and bitter notes, each released at different stages during brewing. Acids come out first, followed by sweetness, and finally bitterness. When extraction stops too soon, you’re left with mostly acids—hence the sour taste.

Under-extraction occurs when water passes through coffee too quickly or isn’t hot enough to dissolve more than the surface-level acids. Over-extraction, on the other hand, pulls too much, including harsh bitter compounds. A well-balanced cup sits in the sweet spot: not sour, not bitter, but harmonious.

“The key to great coffee isn’t fancy gear—it’s consistency and understanding extraction. Most sour cups are simply under-brewed.” — James Hoffmann, World Barista Champion and coffee educator

While some acidity is desirable—especially in light-roast specialty coffees—sourness implies imbalance. Think of it as unripe fruit versus bright citrus: one is pleasant and lively, the other is harsh and unfinished.

Tip: If your coffee tastes sour, don’t reach for sugar immediately. Adjust your brew instead—it’s likely under-extracted.

Key Factors That Cause Sour Coffee

Sourness rarely comes from a single mistake. It’s usually the result of several variables working against proper extraction. Here are the most common culprits:

1. Grind Size Too Coarse

If your coffee grounds are too coarse, water flows through them too quickly, extracting mainly acidic compounds before reaching sugars and body. This is especially common with blade grinders, which produce uneven particle sizes, or when using pre-ground coffee meant for drip machines in a pour-over or French press setup.

2. Water Temperature Too Low

Optimal brewing temperature ranges between 195°F and 205°F (90–96°C). Below this range, water lacks the energy to extract deeper flavor notes. Many kettles don’t heat to boiling, and microwaved water often cools rapidly, leading to weak, sour results.

3. Brew Time Too Short

Each brewing method has an ideal contact time between water and coffee. Too short, and extraction stalls early. For example, a pour-over finished in 1 minute won’t extract fully, while a French press steeped for only 2 minutes will lack balance.

4. Inconsistent Dose-to-Water Ratio

Using too little coffee for the amount of water dilutes the brew and reduces extraction efficiency. A standard ratio is 1:15 to 1:17 (coffee to water), but going beyond 1:18 increases the risk of sourness due to low strength and incomplete extraction.

5. Stale or Poorly Roasted Beans

Freshness matters. Coffee begins losing volatile compounds within days of roasting. Stale beans have fewer sugars and aromatics to extract, leaving behind only the sharper acids. Similarly, poorly roasted beans—especially underdeveloped ones—retain green, grassy flavors that read as sour.

How to Fix Sour Coffee: A Step-by-Step Adjustment Guide

Fixing sour coffee isn’t about guessing—it’s about methodically adjusting one variable at a time. Follow this sequence to dial in your brew:

1. Start with fresh beans. Use coffee roasted within the past 2–4 weeks. Store it in an airtight container away from light and moisture.
2. Weigh your coffee and water. Use a digital scale to ensure consistency. Start with a 1:16 ratio (e.g., 20g coffee to 320g water).
3. Adjust your grind finer. If using a burr grinder, reduce the setting slightly. For pour-over, aim for a medium-fine texture (like table salt); for French press, medium-coarse (like breadcrumbs).
4. Check water temperature. Bring water to just off-boil—around 200°F (93°C). Use a thermometer if unsure.
5. Extend brew time. For pour-over, slow down your pour or increase total brew time to 2:30–3:30 minutes. For French press, extend steeping to 4 minutes before plunging.
6. Taste and repeat. After each change, evaluate the flavor. If still sour, go finer or longer. If it turns bitter, back off slightly.

Tip: Change only one variable at a time. Otherwise, you won’t know what fixed (or broke) your brew.

Brew Method Adjustments for Balanced Flavor

Different brewing methods respond uniquely to adjustments. Here’s how to optimize each for full extraction without tipping into bitterness:

Pour-Over (V60, Kalita Wave)

Pour-overs are sensitive to flow rate and grind size. A sour V60 often means the water drained too fast. Solution: grind finer, use a slower pour, or increase agitation during bloom. Aim for a total brew time of 2:45–3:15.

French Press

Sour French press coffee usually results from under-steeping or coarse grind. Try grinding slightly finer and extending steep time to 4–5 minutes. Stir gently after pouring to ensure even saturation.

AeroPress

The AeroPress is versatile but prone to under-extraction if brew time is too short. Increase immersion time to 2–3 minutes and use a finer grind. Experiment with inverted brewing for better control.

Drip Machine

Many automatic drip machines run too cool. Check if yours reaches 195–205°F. If not, consider upgrading or manually preheating water. Also, use a medium grind and avoid paper filters that restrict flow.

Brew Method	Ideal Grind Size	Brew Time	Common Fix for Sourness
Pour-Over	Medium-Fine	2:30–3:30 min	Grind finer, slow pour, increase agitation
French Press	Coarse	4 min	Grind slightly finer, stir post-pour, extend steep
AeroPress	Fine-Medium	2–3 min immersion	Longer steep, finer grind, full plunge
Drip Machine	Medium	5–6 min total	Preheat water, clean machine, check filter type

Real Example: Fixing a Daily Pour-Over Routine

Consider Sarah, a remote worker who starts her day with a V60 pour-over. Lately, her coffee has tasted sharp and vinegary, almost like lemon juice. She uses a popular light-roast Ethiopian bean, freshly ground with a budget burr grinder, and follows a 1:16 ratio.

Her process: 20g coffee, 320g water, 205°F water, medium grind, 30-second bloom, then pours in two stages. Total brew time: 2 minutes exactly.

The issue? Her grind is slightly too coarse, and her brew time is too short. The water rushes through, extracting only acids. After reading about extraction, she adjusts her grinder one notch finer and slows her second pour. Brew time extends to 2:50. The difference is immediate: the coffee now has floral sweetness, a rounded body, and a clean finish—no sourness.

This small tweak didn’t require new gear—just attention to detail. Within days, Sarah’s morning ritual feels rewarding again.

Essential Checklist for Avoiding Sour Coffee

• ✅ Use freshly roasted beans (within 4 weeks of roast date)
• ✅ Weigh coffee and water for consistent ratios (start with 1:16)
• ✅ Grind coffee just before brewing with a quality burr grinder
• ✅ Use water between 195°F and 205°F (90–96°C)
• ✅ Adjust grind size based on brew time and taste
• ✅ Extend brew time if coffee tastes sour
• ✅ Clean equipment regularly—old oils affect flavor
• ✅ Taste objectively: note brightness vs. sourness

Frequently Asked Questions

Is sour coffee safe to drink?

Yes, sour coffee isn’t harmful—it’s simply under-extracted. While high acidity might bother sensitive stomachs, it doesn’t indicate spoilage. However, if the sourness is accompanied by musty or fermented notes, the beans may be stale or improperly stored.

Can light roast coffee be less sour?

Light roasts naturally have higher acidity, but they shouldn’t taste sour. Proper roasting develops sugars and complexity. If your light roast tastes sour, the issue is likely brewing, not the roast level. Try adjusting grind and brew time before blaming the beans.

Why does my espresso taste sour sometimes?

Sour espresso indicates under-extraction, often due to coarse grind, low dose, or short shot time. Aim for a 1:2 ratio (e.g., 18g in, 36g out) in 25–30 seconds. If the shot runs too fast, grind finer. If it’s slow but sour, check tamping pressure and distribution.

Final Thoughts: Master Your Brew, One Cup at a Time

Coffee brewing is both science and craft. Sourness isn’t a dead end—it’s feedback. Each cup tells you something about your process. When you learn to listen, you gain control over flavor, consistency, and enjoyment.

The tools you need aren’t expensive: a scale, a decent grinder, and attention to timing. With those, you can diagnose issues, make informed adjustments, and consistently brew coffee that’s vibrant, sweet, and satisfying—not sour.

💬 What’s your go-to fix for sour coffee? Share your experience in the comments and help others refine their daily brew!