Why Does My Sourdough Loaf Taste Too Sour And How To Adjust Proofing

Sourdough bread is prized for its complex flavor, chewy texture, and natural fermentation process. But when that tang turns into a sharp, vinegary bite, something in your process may be tipping the balance too far toward acidity. A sourdough loaf that tastes excessively sour isn’t necessarily flawed—it’s a signal from your starter and dough about fermentation conditions. Understanding the science behind sourness and learning how to adjust proofing times, temperatures, and feeding schedules allows you to dial in the perfect balance of flavor.

The sourness in sourdough comes primarily from lactic acid and acetic acid produced by wild yeast and bacteria in your starter. While both contribute to taste, they form under different conditions. Lactic acid delivers a smooth, yogurt-like tang, while acetic acid (the same found in vinegar) brings a sharper, more aggressive sourness. If your bread leans heavily on the latter, it's likely due to extended or cold fermentation, infrequent feeding, or an overdeveloped starter.

By making small, intentional changes to your routine, you can reduce excessive sourness without sacrificing the depth and character that make sourdough special.

What Causes Excessive Sourness in Sourdough?

The primary source of sour flavor in sourdough is bacterial activity—specifically, the metabolic byproducts of Lactobacillus species living symbiotically with wild yeast in your starter and dough. Two key acids dominate the flavor profile:

• Lactic acid: Milder, creamy, slightly tangy—associated with warmer, faster fermentations.
• Acetic acid: Sharper, more pungent, vinegary—favored in cooler, slower conditions.

When your loaf tastes too sour, it usually means acetic acid has become dominant. This happens when:

1. Your starter was used at peak or post-peak ripeness, allowing acids to accumulate.
2. Bulk fermentation lasted too long, especially at room temperature.
3. Final proofing occurred in the refrigerator for more than 12–16 hours.
4. The starter wasn't fed regularly, leading to an acidic buildup.
5. Fermentation took place in a cool environment, favoring acetic acid production.

Temperature plays a crucial role. Cooler temperatures slow yeast activity but don’t inhibit bacteria as much, giving acid-producing microbes more time to work. That’s why overnight cold proofs often yield tangier loaves.

Tip: Use your starter when it’s at its peak—or just before—to minimize excess acidity. Watch for maximum rise and the first signs of deflation.

How Proofing Affects Sourness: Timing and Temperature

Proofing—both bulk fermentation and final proof—directly influences flavor development. The longer the dough ferments, the more organic acids build up. However, not all proofing stages impact sourness equally.

Bulk Fermentation: The Flavor Foundation

This is where most flavor develops. During bulk fermentation, microbial activity is highest. Extending this phase increases sourness, especially if done at warm room temperatures (75–80°F / 24–27°C), which boost overall metabolic activity.

To reduce sourness:

• Shorten bulk fermentation by 30–60 minutes.
• Monitor dough strength and volume rather than relying solely on time.
• Use cooler water (around 70°F / 21°C) to slow fermentation slightly.

Final Proof: Cold vs. Room Temperature

A cold final proof (retardation) in the refrigerator is a common technique for enhancing oven spring and crust development. But it also amplifies sourness because lactic and acetic acid continue forming slowly, even in the cold.

If your bread tastes too sour, consider these adjustments:

• Reduce refrigerated proofing time from 16 hours to 8–10 hours.
• Proof at room temperature for 2–4 hours instead of going straight to the fridge.
• Shape and proof at room temp entirely for milder flavor (best in cooler kitchens).

“Many home bakers don’t realize that retarding dough overnight is one of the biggest contributors to high acidity. For a balanced loaf, try cutting back on cold fermentation time.” — Dr. Karl Brenner, Microbial Fermentation Specialist, UC Davis

Starter Management: The Root of Flavor Control

Your starter is the engine of flavor in sourdough. An unhealthy or inconsistently fed starter will produce unpredictable results—including excessive sourness.

An unfed starter becomes increasingly acidic as it exhausts food and begins consuming its own waste products. Using such a starter introduces a large amount of acid into your dough before fermentation even begins.

Optimal Feeding Routine to Reduce Sourness

Feeding Frequency	Temperature	Flour Type	Expected Sourness Level
Every 12 hours	75–80°F (24–27°C)	All-purpose or bread flour	Mild to moderate
Every 24 hours	Room temp (~70°F / 21°C)	Whole grain (rye, whole wheat)	Moderate to high
Less than daily	Room temp or unheated kitchen	Any, especially whole grain	High (often overly sour)
Twice daily + discard unused	Warm spot (80°F / 27°C)	White flour blend	Lowest sourness, clean fermentation

For a less sour loaf, feed your starter twice daily with equal parts flour and water by weight (1:1 ratio). Use white flour instead of whole grain, which lowers buffering capacity and reduces acid retention. Keep it in a warm spot to encourage fast yeast activity over bacterial dominance.

Tip: Refresh your starter with white flour for 2–3 consecutive feeds before baking to noticeably reduce sourness.

Step-by-Step Guide to Baking a Less Sour Loaf

If you're consistently getting overly sour results, follow this adjusted process to achieve a balanced, nuanced loaf.

1. Feed your starter twice in 24 hours. Feed it in the morning and again 12 hours later. Use 1:1:1 ratio (starter:flour:water) with all-purpose flour.
2. Use the starter at peak rise. It should double in size and pass the float test. Do not wait until it starts collapsing.
3. Keep bulk fermentation short. Aim for 3–4 hours at 75°F (24°C), using stretch-and-folds every 30 minutes during the first 1.5 hours.
4. Limit final proof time. If proofing in the fridge, restrict it to 8–10 hours max. For room temperature, go no longer than 3–4 hours.
5. Bake earlier rather than later. When in doubt, bake the dough slightly under-proofed. Over-proofed dough develops more acid and collapses easily.

This timeline prioritizes yeast activity and structural development over prolonged acidification. You’ll still get good flavor complexity, but without the harsh bite.

Real Example: Adjusting a Weekly Sourdough Routine

Consider Sarah, a home baker who loved sourdough but found her loaves too sour for her family. She maintained her starter once a day with whole wheat flour and always did an overnight cold proof.

Her process looked like this:

• Feed starter in the evening with whole wheat flour.
• Bake the next morning after 12-hour bulk ferment and 16-hour cold proof.
• Result: Very sour, almost pickled flavor.

She made three changes:

1. Switched to feeding her starter twice daily with all-purpose flour.
2. Reduced cold proofing to 10 hours.
3. Shortened bulk fermentation to 3.5 hours with closer monitoring.

Within two bakes, her loaves developed a rich, nutty flavor with only a subtle tang. Her kids started eating it willingly, and she still enjoyed the artisanal quality.

It wasn’t about eliminating sourness—it was about rebalancing the fermentation ecosystem.

Do’s and Don’ts for Controlling Sourness

Do’s	Don’ts
Feed starter regularly (twice daily if possible)	Let starter sit unfed for days
Use starter at peak activity	Use starter after it has collapsed
Proof at room temperature for shorter durations	Always rely on long cold proofs
Use white flour in starter before baking	Stick exclusively to whole grain flours
Monitor dough feel and rise, not just time	Follow recipes blindly without adjusting for climate

FAQ: Common Questions About Sourdough Sourness

Can I fix a too-sour dough once it’s already proofed?

Once the acids are formed, they can’t be removed. However, you can partially neutralize extreme sourness by adding a small pinch of baking soda (1/8 tsp per 500g flour) just before shaping. This reacts with acids and reduces perceived tartness. Use sparingly—it can affect rise and flavor if overdone.

Does hydration level affect sourness?

Indirectly, yes. Higher hydration doughs (above 75%) tend to favor lactic acid bacteria, which produce milder sourness. Lower hydration favors acetic acid. So paradoxically, wetter doughs can taste less sharply sour, though they may still have deep flavor.

Will discarding more starter reduce sourness?

Yes. Regular discarding prevents acid accumulation. If you keep doubling your starter without discarding, the pH drops quickly, creating a more acidic culture. Discard 80–90% before each feed to maintain balance.

Conclusion: Master Your Flavor Through Intentional Fermentation

The sourness of your sourdough loaf isn’t random—it’s a direct reflection of your choices in starter care, timing, and temperature. By understanding how lactic and acetic acid develop, you gain control over the final taste. You don’t have to sacrifice sourdough’s signature complexity to avoid an overpowering tang. Instead, fine-tune your process: feed your starter more frequently, shorten cold proofs, and use white flour to reset acidity.

Great sourdough isn’t just about following a recipe—it’s about listening to your dough and responding with precision. With these adjustments, you can craft loaves that delight with balanced flavor, satisfying texture, and just the right hint of sour.

🚀 Ready to bake a better loaf? Try reducing your cold proof by 4 hours and feeding your starter with white flour for two days. Share your results in the comments!