One of the most common complaints from home bakers isn't that their sourdough tastes bland—it's that it tastes too sour. If you've baked a loaf that made you pucker, or your family politely declined a second slice because the tanginess was overwhelming, you're not alone. The good news? Sourness in sourdough is completely controllable once you understand what creates it.
Despite the name, sourdough bread doesn't have to taste aggressively sour. In fact, many artisan bakeries produce sourdough with a mild, complex flavour that's barely tangy at all. The level of acidity in your bread is the result of specific choices you make throughout the fermentation process—from how you feed your starter to the temperature of your kitchen.
This guide will explain exactly what makes sourdough sour, and give you practical strategies to dial back the acidity and create a milder, more balanced loaf.
What Actually Makes Sourdough Sour?
Sourdough flavour comes from two primary types of acid produced during fermentation: lactic acid and acetic acid.
Lactic acid is produced by lactic acid bacteria (LAB) in oxygen-rich environments. It creates a mild, creamy tanginess—think yogurt or buttermilk. This is the pleasant sourness that adds complexity without overwhelming your palate.
Acetic acid is produced in low-oxygen environments and creates that sharp, vinegary punch. It's the same acid found in vinegar, and it's what makes overly sour bread taste harsh and one-dimensional.
The ratio of these two acids determines your bread's flavour profile. When acetic acid dominates, your bread tastes aggressively sour. When lactic acid is more prominent, you get a milder, more nuanced tang. Your job as a baker is to create conditions that favour lactic acid production over acetic acid.
The 6 Factors That Control Sourness
1. Fermentation Temperature
This is the single most powerful lever you have for controlling sourness.
Warmer temperatures (24-27°C / 75-80°F) speed up fermentation and favour lactic acid bacteria. The dough ferments faster, so less acetic acid accumulates. Your bread will be milder.
Cooler temperatures (18-21°C / 64-70°F) slow down fermentation and shift the balance toward acetic acid production. Long, cold fermentations create more sour bread.
What to do: If your bread is too sour, ferment your dough in a warmer spot. Move it near (not on) a heating vent, use a proofing box, or place it in a turned-off oven with the light on. Aim for 24-26°C (75-78°F) during bulk fermentation.
2. Fermentation Time
The longer your dough ferments, the more acid accumulates—particularly acetic acid.
Many bakers over-ferment without realizing it, especially when using long cold retard methods. A 12-hour cold retard in the refrigerator will produce a tangier loaf than a 4-hour version, even if both are properly proofed.
What to do: Shorten your fermentation times. If you typically do an overnight cold retard of 12-16 hours, try 8 hours instead. If you're doing a room-temperature final proof, watch for visual cues (dough has risen 30-50%, jiggles slightly, passes the poke test) rather than following a set time.
3. Starter Feeding Ratio and Maturity
An older, hungrier starter produces more acetic acid. If you feed your starter and wait 12-24 hours before using it (well past its peak), it will be very acidic and will make your bread sour.
A young, recently-fed starter (used at peak rise, typically 4-8 hours after feeding) produces milder bread because it hasn't had time to generate excess acid.
Your feeding ratio also matters. A 1:1:1 feeding (equal parts starter, flour, and water) runs out of food faster and becomes acidic more quickly than a 1:5:5 or 1:10:10 feeding, which stays active longer with less acid buildup.
What to do: Use your starter at its peak (when it has doubled or tripled and is bubbly and domed on top). Don't let it sit for hours after peaking. If you maintain your starter with small feedings, consider increasing the ratio to 1:5:5 (for example, 20g starter + 100g flour + 100g water) so it stays sweeter longer.
4. Hydration Level
Lower hydration doughs (60-70% water to flour) tend to produce more acetic acid because the thicker consistency limits oxygen circulation throughout the dough. Less oxygen = more acetic acid.
Higher hydration doughs (75-85%) allow for better oxygen distribution, favouring lactic acid bacteria and milder flavours.
What to do: If you're working with a stiff dough, try increasing hydration by 5-10%. A 70% hydration dough will be noticeably less sour than a 65% version, all else being equal.
5. Whole Grain Flour Percentage
Whole grain flours (whole wheat, rye, spelt) are more nutritious for bacteria and yeast, which means they ferment faster and produce more acid—especially acetic acid.
A 100% whole wheat sourdough will almost always be more sour than a bread made with mostly white bread flour.
What to do: Reduce the percentage of whole grain flour in your recipe. Try replacing half of your whole wheat flour with white bread flour. You'll still get nutritional benefits and complexity, but with less acidity.
6. Salt Percentage
Salt regulates fermentation speed and bacterial activity. Too little salt (less than 1.8% of flour weight) allows bacteria to run wild, producing more acid and sourness.
Standard salt percentages (2-2.2% of flour weight) help keep fermentation balanced.
What to do: Check your salt percentage. If you're using 1.5% or less, increase it to 2%. This won't eliminate sourness, but it will slow acid production and give you more control.
The Quick-Fix Strategy: Make a Milder Loaf Tomorrow
If you want immediate results, here's a simple game plan:
Step 1: Feed your starter in the morning and use it at peak rise (4-8 hours later), not after it's collapsed.
Step 2: Mix your dough and ferment it in a warm spot (24-26°C / 75-78°F).
Step 3: Watch for visual cues during bulk fermentation. When the dough has increased by 50% and shows bubbles on the surface, shape it.
Step 4: Skip or shorten the cold retard. Either bake the same day after a short final proof, or refrigerate for just 4-6 hours instead of overnight.
This approach prioritizes speed and warmth—both of which reduce acetic acid production and create a milder loaf.
When Sourness Is Actually a Good Thing
Not all sour bread is a mistake. Some styles—like San Francisco sourdough or German rye breads—are meant to be tangy. Acetic acid also extends shelf life and adds structural complexity to whole grain loaves.
The goal isn't to eliminate sourness entirely, but to control it so you can create the flavour profile you want. Once you understand the levers, you can adjust them to match your taste.
Troubleshooting: My Bread Is Still Too Sour
If you've made the changes above and your bread is still too tangy, consider these less common issues:
Your starter might be too acidic overall: Try maintaining it with more frequent feedings (twice a day instead of once) and higher ratios (1:5:5 or 1:10:10). After a week of this, it should taste sweeter and produce milder bread.
You're over-proofing: Dough that has fermented too long will always be sour, even if other conditions are right. Pull back on fermentation time and look for subtle signs of readiness, not dramatic rise.
Your water is chlorinated: Chlorine can stress your yeast, allowing bacteria (which produce acid) to dominate. Use filtered or dechlorinated water.
The Bottom Line
Sourdough doesn't have to taste like a vinegar bomb. By fermenting warmer, using your starter at its peak, shortening fermentation times, and increasing hydration, you can bake bread that's complex and flavourful without being aggressively sour.
Experiment with one variable at a time so you can learn how each one affects your specific setup. Within a few bakes, you'll have complete control over your bread's acidity—and you'll be able to dial in exactly the flavour you're after.