Sourdough starter mold and smells: when to throw it away
Fuzzy spots, or pink, orange or red streaks, are mold. Throw it away, jar and all. Don’t scrape it off: mold grows roots you cannot see. A sour, vinegar or nail-polish smell and grey liquid on top are normal — those mean it is hungry.
Mold is fuzzy or furry, or shows as pink, orange or red streaks, or black fuzz. Any of these: throw it away, jar and all.
2
Do not scrape it off
Mold spreads threads through the whole starter. Scraping off the top does not make it safe.
3
Know what is normal
Grey or brown liquid (hooch), a dry crust on top, and sour, vinegary, cheesy or acetone smells are all normal signs of a hungry starter.
4
Start again, cleanly
Use a clean jar and fresh flour. A new starter usually takes 7–14 days — the calculator above shows the dates.
Why
Mold is a different organism from the yeast and bacteria of a healthy starter. It can make toxins you cannot see, taste or bake away — which is why the only safe answer is the bin.
Questions
Can I save a moldy starter?
No. Throw it away, jar and all. It is never worth the risk.
Is a dry crust on top mold?
No — a dry, leathery skin is just starter that dried out. Peel it off and feed what is underneath. Fuzz or colored streaks are mold.
Is a pink or orange streak ever okay?
No. Pink, orange or red means throw it away, jar and all.
How do I stop it happening again?
A clean jar at every few feeds, a loose lid, and regular feeding. A hungry, neglected starter is where mold gets its chance.
It remembers your starter, plans every bake around your day and reminds you at each step — no alarms at 3 am. Coming to the iPhone App Store before Christmas.
Get the app the day it launches
One email when the iPhone app is on the App Store, then a short baking tip now and then.
Your email
No spam, and never shared. Every email has a one-click unsubscribe.