Sourdough Bread Too Sour? How to Control Acidity

Sourness in sourdough is not an on/off switch — it is a dial. Every sourdough loaf lands somewhere on a spectrum from barely-there tang to face-puckering sharp, and the baker controls where it lands. If your bread is consistently too sour, you are not doing anything wrong in the mechanical sense. You are just giving your bacteria the conditions they prefer for making acid.

The fix is straightforward once you understand which acid is responsible and what drives its production.

The Two Acids: Lactic vs. Acetic

Sourdough sourness comes from two organic acids produced by lactic acid bacteria (LAB) in your starter. They taste completely different and are produced under different conditions.

All five major bread authorities agree on this relationship. It is one of the most consistent principles in the bread science literature. Warm and wet conditions favor lactic acid (mild). Cool and dry conditions favor acetic acid (sharp).

This means you have direct control over the sourness of your bread through three levers: temperature, hydration, and time.

Lever 1: Temperature

Temperature is the most powerful lever. The bacteria responsible for the sharp, vinegary acetic acid are more active at cooler temperatures (65-70 degrees Fahrenheit), while lactic acid bacteria — the ones that produce the mild, yogurt-like sourness — thrive at warmer temperatures (75-85 degrees Fahrenheit).

If your bread is too sour:

• Ferment your dough warmer. Target 78-82 degrees Fahrenheit for bulk fermentation, the range Chad Robertson uses for his Tartine country bread.
• Feed your starter with warmer water. Ken Forkish uses 85-90 degrees Fahrenheit water for his levain builds.
• Keep your starter in a warmer spot between feedings. A kitchen at 75 degrees Fahrenheit produces milder starter than one at 65 degrees Fahrenheit. See our feeding schedule guide for more on maintenance routines.

If your bread is not sour enough:

• Ferment at cooler temperatures (65-70 degrees Fahrenheit).
• Use cold retarding — refrigerate shaped loaves overnight at 37-40 degrees Fahrenheit. The lactic acid bacteria slow down dramatically, but acetic acid bacteria remain slightly active at refrigerator temperatures, gradually building sharp tang.
• Feed your starter less frequently, allowing more acid to accumulate between feedings.

Lever 2: Starter Hydration

The water content of your starter culture directly affects which acids dominate.

A liquid starter (100% hydration — equal weights flour and water) favors lactic acid production. The wet environment promotes the bacteria that produce mild, creamy sourness.

A stiff starter (60% hydration — significantly more flour than water) favors acetic acid production. The drier environment shifts the bacterial balance toward the organisms that produce sharp, vinegary tang.

Hamelman maintains both liquid and stiff levain builds in his bakery for exactly this reason — they produce different flavor profiles. His liquid levain at 100-125% hydration produces bread with mild, balanced acidity. His stiff levain at 60% hydration produces bread with more assertive, complex sourness.

If your bread is too sour: Switch to a 100% hydration starter (equal weights flour and water at each feeding). This is the standard maintenance hydration for most home bakers and naturally tilts the flavor toward mild.

Lever 3: Fermentation Time

Longer fermentation means more total acid production. This is simple math — the bacteria keep producing acid as long as they have food, and time gives them more opportunity to accumulate it.

The difference between a 3-hour bulk fermentation at 80 degrees Fahrenheit and a 12-hour bulk at 68 degrees Fahrenheit is not just about rise. The extended fermentation produces dramatically more acid, shifting the flavor profile toward sour.

If your bread is too sour:

• Shorten your bulk fermentation. Robertson’s country bread targets just 3-4 hours of bulk at 78-82 degrees Fahrenheit.
• Reduce the percentage of pre-fermented flour. Less mature starter in the final dough means less accumulated acid.
• Feed your starter more frequently. A starter fed every 12 hours accumulates less acid than one fed every 24 hours.

The Young Leaven Concept

This is Chad Robertson’s most distinctive contribution to sourdough technique and it directly addresses the sourness problem.

Robertson seeds a fresh leaven build with just 1 tablespoon of mature starter into 200g flour and 200g water. He then uses this leaven when it passes the float test — typically 8-12 hours later, but before it has fully matured and reached peak acidity.

The result: the yeast is active (providing lift), but the acid has not accumulated (keeping the flavor mild). This is why Tartine bread does not taste “sourdough” despite being 100% naturally leavened. It has complex wheat flavor and subtle fermented character without aggressive tang.

The float test is the go/no-go signal. Drop a small spoonful of leaven into water. If it floats, the yeast is producing enough CO2 to be buoyant — it is ready. If it sinks, give it more time. But do not wait much beyond the float point, or acid accumulates.

If your bread is consistently too sour, this single change — using younger leaven — may be the most impactful adjustment you can make. For the full technique, see our beginner sourdough recipe.

Your Starter’s Health Matters

A well-maintained starter produces balanced, pleasant sourness. An over-fermented or neglected starter produces harsh, vinegary tang. If your starter is struggling, fix it before troubleshooting your bread.

Signs of a healthy starter:

• Pleasantly sour, yeasty, slightly alcoholic aroma (Hamelman)
• Yogurt or mild cheese smell (Robertson)
• “A hot rush of alcoholic perfume” when you lift the lid (Forkish)
• Gassy, weblike internal structure when you pull it apart

Signs of an over-acidic starter:

• Strong vinegar smell — acetic acid dominance
• Very loose, liquid consistency
• Slow to rise after feeding
• Produces bread with harsh, one-note sour flavor

How to reset an over-acidic starter: Feed it twice daily for 3-4 days at warm temperature (78-80 degrees Fahrenheit) with a higher ratio of fresh flour to mature starter. A 1:5:5 ratio (1 part starter, 5 parts flour, 5 parts water by weight) dilutes the acid aggressively while keeping the culture alive. Within a few days, the balance shifts back toward yeast dominance and milder acidity. For the underlying science, see sourdough starter science.

The Complete Fix: A Low-Sourness Protocol

If you want bread with minimal sourness, combine all three levers:

1. Feed your starter with warm water (85 degrees Fahrenheit) at 100% hydration, using a 1:5:5 ratio, 8-12 hours before mixing.
2. Build a young leaven. Use just 1 tablespoon of starter to seed 200g flour + 200g water. Use when it passes the float test.
3. Mix and bulk ferment warm. Target 78-82 degrees Fahrenheit for the dough. Fold during the first 2 hours.
4. Keep bulk fermentation short. Aim for 3-4 hours at warm temperature — just enough for a 20-30% volume increase.
5. Shape and bake the same day if possible, or retard for no more than 8-10 hours if you must delay.

This protocol maximizes lactic acid (mild) while minimizing acetic acid (sharp) and total acid accumulation. The bread will taste of complex wheat and subtle fermentation, not aggressive tang.

The Flip Side: Making Bread More Sour

Some bakers want more sourness. If that is you, reverse the protocol:

• Feed your starter at 60% hydration (stiff) with cool water
• Let the leaven fully mature before use — wait past the float point
• Bulk ferment at cooler temperatures (65-70 degrees Fahrenheit) for longer durations
• Cold retard overnight at 37-40 degrees Fahrenheit
• Use a higher percentage of pre-fermented flour in the final dough

The result will be a more assertive sourdough with pronounced acetic tang. This is a legitimate flavor target — San Francisco sourdough’s iconic sharp sourness comes from exactly these conditions. See our guide to cold fermentation for more on overnight retarding.

Common Mistakes That Increase Sourness

Feeding too infrequently. A starter that goes 24+ hours between feedings accumulates significant acid. If you bake frequently, feed twice daily. If you bake weekly, store your starter in the fridge and revive with two feedings before use.

Using too much mature starter in the dough. More starter means more acid introduced at the start. Keep your leaven percentage at 15-20% of total flour.

Fermenting in a cold kitchen. If your kitchen is 65 degrees Fahrenheit, your dough is producing acetic acid even if you intended a short fermentation. Warm the environment: use your oven with the light on, a proofing box, or a warm spot near a radiator.

Long overnight retards with young dough. If the dough did not ferment enough before refrigeration, the bacteria continue producing acid in the cold for 12-16 hours. Either bulk ferment fully before shaping and retarding, or limit cold retard to 8-10 hours.

For a broader look at what can go wrong, see our bread troubleshooting guide.

The Bottom Line

Sourness is not random. It is the predictable result of temperature, hydration, and time — and you control all three. If your bread is too sour, go warmer, go wetter (in your starter), go shorter, and use younger leaven. If you want more tang, go cooler, go stiffer, go longer.

Every loaf is a data point. Adjust one variable at a time and taste the difference.