What You’ll Learn
- What pH measures.
- Why starter pH falls.
- How acidity shapes the microbial ecosystem.
- Why pH differs from total acidity.
- Whether home bakers need to measure it.
Quick Answer
pH measures how acidic or alkaline something is. As sourdough starter ferments, acids produced by bacteria lower the pH. A mature starter is acidic enough to favour the sourdough ecosystem, but pH alone does not tell you whether a starter is ready to bake with.
This lesson is part of our Science of Sourdough section: “Understand what’s happening inside your dough.”
What Is pH?
pH is a logarithmic scale used to describe acidity or alkalinity.
Why Sourdough Becomes Acidic
Lactic acid bacteria produce organic acids during fermentation.
Why Acidity Matters
The acidic environment favours microorganisms adapted to sourdough and discourages many others.
pH vs Sour Taste
Two doughs with similar pH can taste different because flavour depends on the types and amounts of acids present.
pH Through the Feeding Cycle
Fresh feeding raises the pH relative to a hungry starter, then acidity develops again as fermentation progresses.
Do You Need a pH Meter?
No. Most home bakers can judge starter and dough successfully using rise, aroma, texture and time.
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
pH can be useful for experimentation, but it is easy to turn a helpful measurement into another number to obsess over.
Bake Slower Tip
Use pH as supporting data, not as a replacement for reading the dough.
Common Mistake
Do not assume lower pH automatically means better fermentation.
Today You Learned
- pH measures acidity.
- Sourdough becomes more acidic as it ferments.
- Acidity shapes the microbial environment.
- pH and sour flavour are not identical.
- Most home bakers do not need a pH meter.
Frequently Asked Questions
What pH should starter be?
There is no single number that defines readiness across all starters.
Does pH tell me when to bake?
Not by itself.
Can I measure with strips?
Yes, though precision is limited.
Why does pH change after feeding?
Fresh flour and water dilute accumulated acids.
Is very low pH bad?
Excessive acidity can weaken dough and affect starter performance.
Tools & Ingredients Mentioned in This Guide
These products are directly related to the measurements, ingredients or starter care discussed in this lesson.
Turn the Science Into Better Bread
Measure pH if you enjoy the science, but do not let it replace practical baking judgement.
Continue Learning
Next lesson: Enzymes in 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.