What You’ll Learn
- Which colours indicate contamination.
- Why mould cannot simply be scraped off.
- How contamination differs from hooch.
- How to clean and restart safely.
- How to reduce the risk in future.
Quick Answer
If your sourdough starter develops pink or orange staining, fuzzy mould or a rotten smell, discard the entire starter and clean the container thoroughly. Do not scrape off the visible area and continue using the rest. Start again from a safe backup or a fresh established culture.
This lesson is part of our Sourdough Starters section: “Learn how to care for the heart of every loaf.”
Pink or Orange Starter
Pink or orange patches or streaks are not normal fermentation colours and should be treated as contamination.
Fuzzy Mould
Green, blue, white, black or other fuzzy growth is mould. Discard the whole culture.
Why You Should Not Scrape It Off
Visible growth may not represent the full extent of contamination. Removing only the surface does not guarantee the remainder is safe.
What Is Not Mould?
Grey or brown hooch, dried flour around the rim and normal darkening can look alarming but are different from fuzzy growth.
How to Clean Up
Dispose of the starter, wash the jar thoroughly and sanitise or replace tools that contacted the contaminated culture.
How to Prevent It
Use clean utensils, avoid food contamination, keep the jar covered appropriately and maintain regular feeding.
From Our Workshop
Starter is inexpensive to replace. Your health is not. If you are debating whether pink growth is ‘probably fine’, that is the moment to discard it.
Bake Slower Tip
Keep a dried backup of a healthy starter so contamination is an inconvenience rather than a disaster.
Common Mistake
Never taste a mouldy or unusually coloured starter to test whether it is safe.
Today You Learned
- Pink and orange growth are contamination signs.
- Fuzzy mould means discard the whole starter.
- Do not scrape mould off and keep the remainder.
- Hooch is different from mould.
- A dried backup makes restarting easy.
Frequently Asked Questions
Can I save starter underneath the mould?
No. Discard the whole culture.
Is a white film always mould?
Not necessarily, but if you cannot confidently identify it, prioritise safety.
Is grey liquid mould?
No, liquid is more likely hooch or separation.
Can the jar be reused?
Yes if it can be thoroughly cleaned and sanitised.
How do I start again?
Use a safe dried backup, starter from another baker or a fresh established culture.
Need the Right Starter Setup?
If you need to restart, begin with a clean jar and a trusted culture rather than taking chances with contamination.
Continue Learning
Next lesson: Return to Sourdough Starters
A simple starter check
Keep one variable stable while you diagnose the starter. Record the flour, feeding ratio, room temperature and approximate rise after each feed. A short three-feed record is usually more useful than changing flour, ratio and temperature all at once.