What You’ll Learn
- Which acids create sour flavour.
- How lactic and acetic acid differ.
- How starter condition affects taste.
- How fermentation time changes flavour.
- How to make bread milder or sharper.
Quick Answer
Sourdough tastes sour because lactic acid bacteria produce organic acids during fermentation. Lactic acid tends to give a softer, yoghurt-like acidity, while acetic acid contributes sharper notes. Feeding ratio, starter condition, flour, time and temperature all influence the final balance.
This lesson is part of our Science of Sourdough section: “Understand what’s happening inside your dough.”
The Main Acids
Lactic and acetic acids are two important contributors to sourdough flavour.
Lactic Acid
This often contributes a softer, rounded acidity.
Acetic Acid
This is associated with sharper, more vinegar-like notes.
Starter Feeding
A well-fed starter begins each cycle with less accumulated acidity than a neglected one.
Time
Longer fermentation generally allows more acid development.
Temperature
Temperature changes microbial activity and can influence flavour balance.
Flour
Wholegrain and rye bring their own flavour and can change fermentation behaviour.
Making Sourdough Milder
Use a fresh active starter and avoid unnecessarily prolonged fermentation.
Why This Matters in the Kitchen
The science matters only when it helps you make better decisions. Use it to understand what you can see, smell and feel in your starter and dough.
From Our Workshop
Good sourdough does not need to taste aggressively sour. We prefer acidity that supports the grain rather than overwhelms it.
Bake Slower Tip
If the bread is too sour, fix starter condition and fermentation before adding sweeteners.
Common Mistake
Do not assume old starter automatically makes ‘better’ sourdough because it tastes sharper.
Today You Learned
- Sourness comes mainly from fermentation acids.
- Lactic and acetic acids taste different.
- Starter condition affects acidity.
- Time and temperature change flavour.
- Sourdough can be mild or strongly sour.
Frequently Asked Questions
Is sourdough supposed to taste very sour?
No.
Why is mine suddenly sharper?
Fermentation time, temperature or starter condition may have changed.
Does rye make it more sour?
It can intensify flavour and fermentation, but acid production is still the main cause.
Can I make mild sourdough?
Yes.
Does refrigeration increase sourness?
Long cold fermentation can deepen acidity.
Turn the Science Into Better Bread
Once you understand where acidity comes from, sourness becomes something you can shape rather than simply accept.
Continue Learning
Next lesson: Return to Science of Sourdough
What this means at the bench
The useful question is not only what is happening scientifically, but what you can observe. Connect the science to changes in rise, aroma, acidity, dough strength, extensibility and fermentation speed in your own kitchen.