There’s Mold in My Starter – Can I Still Save It?

A: Discovering mold on your sourdough starter is a bummer, and unfortunately, in most cases the starter cannot be saved. Visible mold growth is a clear signal to discard your starter and start fresh. Health and food safety come first – moldy starter could contaminate your bread or make you sick, so it’s not worth trying to rescue. Here’s what you need to know:

• How to identify mold: Mold on starter might appear as fuzzy spots in colors like white, green, blue, or black, similar to bread mold. It could also manifest as an orange or pink film or streak, which indicates harmful bacteria or mold growth as well. Mold can grow on the surface of a starter or even on the sides of the jar above the starter if residue is left there. If you see anything brightly colored (other than tan/gray) or any fuzzy patches, that’s mold. The photo in the previous answer (with the red circle) showed an orange patch – that starter was mold-infected and had to be thrown away. Trust your eyes and nose: mold may also give a musty or off smell.
• No, you can’t just scrape it off: Unlike something like cheese where people cut mold off, a wet fermented mixture like starter is thoroughly penetrated by mold. The microscopic filaments (mycelium) can run unseen through the starter. Scraping the top won’t remove spores that have diffused. So even if only one spot has mold, the safest course is to ditch the entire batch. Think of it as starting new with the knowledge you gained – a fresh starter can be cultivated in 5-7 days, and it’s better than risking mold toxins.
• What causes mold? The most common cause is severe neglect – leaving a starter unfed at room temperature for too long (often weeks) so that its acidity drops and unwanted organisms take over. Other factors can include contamination (e.g. something foreign fell into the jar), or using an unclean jar or utensil. Warm, humid environments can encourage mold spores too. If you live in a hot and humid climate and keep your starter on the counter, mold is more of a risk (especially if near a fruit bowl or compost where mold spores are abundant).
• Can I prevent it? Yes – maintenance and hygiene are key. A well-fed, mature starter is highly acidic, which naturally wards off most bad microbes. So the number one prevention is regular feedings (or proper refrigeration for long storage) so that the starter’s friendly yeast and lactic acid bacteria keep control of the environment. Also: always use a clean jar and spoon. When you feed, if you notice dried starter clinging to the sides of the jar above the level of the starter, wipe it off if possible – those dry bits can harbor mold over time. Keep your starter covered to prevent insects or debris carrying mold spores from getting in (a lid or even plastic wrap loosely set on top is fine). If you’ve had mold issues in a warm kitchen, consider storing the starter in the fridge and only bringing it out to feed a couple days before baking. And as a tip from experience: don’t store your starter right next to ripening fruit or a trash can – minimize exposure to airborne spores.
• If mold happens: Unfortunately, you do need to say goodbye to that starter. Dispose of it entirely. To avoid cross-contamination, wash the jar/bowl thoroughly with hot soapy water (or replace it) before making a new starter or using it for anything else. Some dedicated bakers keep a small backup of dried starter precisely in case mold strikes – so they can quickly rehydrate the backup and continue. If you don’t have that, you’ll be starting from scratch. It’s okay; it happens to many of us at least once. Learn from it and adjust your starter care routine if needed (feed more often, etc.).

In summary: Visible mold = non-negotiable discard. It can’t be salvaged safely. The good news is that if you follow good starter practices, mold is relatively rare. Many bakers go years or decades without ever seeing mold in their starter. Keep it acidic and happy, and your starter will be a hardy kitchen companion. If you do lose one, take it as an opportunity to start a new, strong culture – and perhaps keep the new one in conditions less favorable to mold. Within a week or so, you’ll have an active starter again. No need to feel bad – even professional bakers occasionally encounter a moldy starter and have to refresh their mother cultures.

(Related: To ensure your starter stays healthy, see “Can I Overfeed or Underfeed My Sourdough Starter?” for tips on feeding frequency and amounts, as underfeeding can weaken a starter and potentially invite mold.)