Bad Sourdough Starter – How to Tell and What to Do

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By Kyrie Luke

The good news is that it’s very difficult to have a bad sourdough starter that’s beyond repair. The bad news is that, yes, sourdough starters can go bad. You have a bad sourdough starter if it was heated above 140 degrees F or if it has developed mold.

However, discoloration aside from pink or orange may just be a sign of hooch which is totally safe. In this post, I’ll address all the common sourdough starter concerns such as color, mold, smells, and much more.

Related: How to Fix Dense Sourdough Bread

Related: Sourdough Starter from Scratch in 7 Days

This post contains affiliate links, which means I make a small commission at no extra cost to you. See my full disclosure here.

Can sourdough starters go bad?

Yes, sourdough starters can go bad, however, they’re very resilient and what may look like a dead sourdough starter probably isn’t. See the signs below of a dead sourdough starter vs. a revivable starter.

Signs of a Revivable Sourdough Starter

Most of the weird, or unpleasant activity in sourdough starters can be repaired with regular feedings. Further, you can put sourdough under a lot of stress and will likely be able to revive it.

1. It has runny, brown, or black liquid on top

This is very common and it’s called “hooch.” Hooch is a type of alcohol that forms on top of sourdough starters as a result of the growth of yeast. Hooch is perfectly safe and is even edible. You can either stir it into the starter or pour it off and feed your starter as usual.

2. It smells bad

Good sourdough starters smell sweet, like bread, or slightly sour (like sourdough). However, after some mild neglect, they can develop an acidic, quite sour, or just plain funky smell. Unless you see signs of mold (see the section below to determine if it’s actually molded) then you can revive your starter. Funky smells are usually just a sign of a hungry starter.

3. It was frozen

Yes, you can freeze sourdough starter. It’s not the best way to preserve it (see dehydrating method below), but it can be done for short periods of time. It’ll take a while to revive it (see method below), but usually, you’ll come out with an alive starter after freezing for a short period of time.

4. There’s a white powdery film on top

This is likely Kahm yeast and is not the same as mold. It’s sort of foamy and powdery and can float on top of hooch. You can save this starter as Kahm yeast is perfectly safe. See the sourdough starter troubleshooting method below.

5. Has a crusty top

A crusty top just means your sourdough starter needs to be stirred. To avoid a crusty top, you can cover your starter with a damp tea towel instead of a dry towel.

Signs of a Bad Sourdough Starter

These qualities are indicative of a starter beyond repair. There are always exceptions to the rule, but, in general, there’s no coming back from these and you’ll need to start over.

1. You heated it above 120 degrees

It happens all the time – someone wants to quickly activate their starter for a recipe so they put it in the oven with the light on, forget it’s in there, preheat the oven, then boom. Dead starter. Yeast dies at around 140F (maybe even a little lower) so don’t let it get in contact with hot environments like that. Keep it at a cozy 70F (give or take a few degrees).

2. Brightly colored streaks

These are signs of mold and happen when the starter has been severely neglected. When mold forms on sourdough starters, it means the bacteria in the starter has lost it’s ability to fend off mold. It’s best to discard your starter and start over. Hooch is not mold, see the sections below to determine if what you’re experiencing is hooch or mold. Head to this post for a tutorial on how to make a sourdough starter from scratch in 7 days.

3. It’s inactive after many feedings

If you’ve fed your starter every day for a week (maybe twice a day) trying to revive it and there is still no activity, it’s gone bad and it’s time to start over. Starters indicate activity by becoming very bubbly, sometimes foamy on the top, and growing up to double in size.

How to Avoid Letting your Sourdough Starter Go Bad

1. Don’t use aluminum or copper to store your starter – see the section below on the best container to store your starter.
2. Regular feedings – feed your starter regularly for the healthiest, most active sourdough.
3. Store in the fridge when not using – if you aren’t going to be using your sourdough starter for more than 2 days, it’s best to store it in the fridge.
4. Don’t use an airtight container – using an airtight container can ferment the starter rather than allowing it to collect the natural yeast from the environment. Keep a loose-fitting lid or covering overtop.
5. Keep at room temperature when using – when you’re actively using your sourdough starter, keep it as room temperature, but try not to let it get above 75 degrees or so.
6. Use fresh, unbleached flour – Sometimes flour can contain contaminants that can cause mold in your starter. Avoid this by using fresh, unbleached flour. Using very old flour that’s been in your pantry for years is never a good idea.
7. Weigh ingredients – If you’re dealing with a high-maintenance starter, or trying to revive one, it’s a good idea to weigh your ingredients in grams so you have accurate proportions.
8. Use clean utensils and containers – this prevents the contaminants that cause the growth of bad bacteria.
9. Use filtered water – using filtered water will prevent contaminants from the water spoiling your sourdough starter.

Related: Berkey vs Brita Water Filters

Related: List of Bread-Making Essentials

How to Troubleshoot a Bad Sourdough Starter

If your starter is just looking a little funky but doesn’t have the qualities of a “dead starter” listed above, you can repair it by using the following method.

1. If you have hooch on your starter you can pour it off.
2. Discard some of the sourdough starter. Depending on how much you currently have, I’d only keep about 100 grams.
3. Feed the remaining starter with 100g of flour and 100g of water. Let it sit out at room temp for around 12 hours.
4. Remove 50g of that starter and feed it another 100g of flour and 100g of water. Let it sit for another 12 hours.
5. If your starter has doubled by now, it’s revived! Yay! If not, repeat step 4 until it does. *If after several days (up to a week) of feedings it doesn’t show signs of activity, then you’re dealing with a sourdough stater beyond repair and you’ll need to start over.

Is your Sourdough Starter Moldy or is it Something Else?

If your starter is moldy, you do need to toss it and start over. This means that the bad bacteria has overtaken your starter to the point that the good bacteria cannot ward it off.

Your sourdough starter is moldy if…

1. Pink, yellow, or orange streaks indicate mold. They can be muted in color, but are reminiscent of those colors.
2. Fuzzy growth means mold. If you notice your starter has a fuzzy, mold-like layer over the top, it’s likely mold.

Your starter is not (necessarily) moldy if…

All of the below can be true without the presence of mold. However, they can also be true with the presence of mold. So, if there is mold (see above) then toss it, if not, revive it.

1. White powdery foam on top. This is Kahm yeast and perfectly safe and a normal result of growing natural yeast from wheat. Just scrape it off and feed the sourdough.
2. Black or brown liquid. This is called hooch, it’s also safe and a natural process of alcohol formation. Either stir it in or pour it off and feed the starter.
3. Smells bad. Your starter will take on a multitude of smells throughout its life – some pleasant and some very unpleasant. A bad-smelling sourdough starter means it is very hungry and needs to be fed. If there are no signs of mold, it’s totally safe to feed and bake with.
4. Has a crust on top. Crusts form when it’s kept in a warm environment with little humidity and hasn’t been stirred. To prevent the crust, either stir more frequently (every 12 hours) or keep a damp towel over top.

How to prevent a moldy sourdough starter

1. Keep food or soap residue out. Sometimes food can get inside if you’re using the same utensil to scoop your starter as you do to prepare food – avoid this. Further, thoroughly wash off all soap from utensils.
2. Avoid severe neglect. Going a week or so without feeding your sourdough starter while it’s in the fridge should not cause mold in a healthy starter. However, leaving a starter on the counter for a week or two with no feedings will likely result in a bad sourdough starter.
3. Keep it away from mold sources. If something is rotting next to your starter, such as fruit, that could encourage mold growth on your starter.
4. Stay away from high humidity environments. Extreme humidity can also encourage mold growth.
5. Use fresh flour and filtered water for feedings. Contaminants in the flour or water you’re using to feed your starter can cause mold – be sure to use fresh, unbleached flour and filtered water. We use a Berkey water filter to filter our water. Shoot me an email below and I’ll send you a discount.

How to Dehydrate your Sourdough Starter

To prevent ever having to start from scratch, should your sourdough ever go bad, then take some of your active sourdough starter, dehydrate it, and store it in a jar. You’ll be able to reactivate it more quickly than starting from scratch.

Easy method for dehydrating a sourdough starter

1. Feed your starter as usual.
2. Once it’s active, prepare a baking sheet with a layer of parchment paper.
3. Use a clean spatula to spread a thin layer of active sourdough across the paper (covering most of the surface). Use a piece of plastic wrap to loosely cover the starter to keep debris away.
4. Let it sit at room temperature for 18-48 hours in a dry area.
5. You’ll know it’s ready to store when it’s dry and crisp like a cracker or chip.
6. Store indefinitely in an airtight container in a cool dry area.
7. Rehydrate your sourdough by placing about 14 grams of sourdough into a glass bowl of 28 grams of lukewarm water. Stir until the chips are completely saturated with water.
8. Once the chips have melted into the water (about 4 hours later) add another 14 grams of lukewarm water and 28 grams of unbleached flour, stir and let sit for another 4 hours or so.
9. Add another 84 grams of lukewarm water and 84 grams of unbleached flour, stir and let it sit again for several hours. You should start to notice activity by this point.
10. Repeat step 9 until you get a starter that is doubling in size and looking very active. You may need to discard some first.

Sourdough starter smells bad

Your sourdough starter may smell bad – it could smell like alcohol, acetone, feet, vomit, and a million other things too. Unless this smell is accompanied by mold (see section above on mold) all this means is that it’s very hungry.

Liquid on Top of Sourdough Starter

It’s very common for a mildly neglected sourdough starter to form what’s called “hooch” on top. This is a layer of clear, black, or brown liquid that forms on top which is an alcohol that’s produced from the yeast growth.

Hooch is actually edible, so you can mix this in with the starter, or pour it off and feed it as normal. Either way, your starter isn’t bad when it has hooch.

Can Bad Sourdough Starter Make You Sick?

Yes, bad sourdough starter, especially if caused by mold, can make you sick and needs to be tossed out. However, it’s important to make sure your starter is actually moldy and not something else, like hooch.

Best Container For Sourdough Starter

1. Clean – prevent mold by using a clean container with no soap or food residue.
2. Not airtight, but with a lid – you want a container that isn’t airtight but does have some sort of lid to prevent debris from getting inside.
3. Non-reactive – definitely no aluminum or copper containers, and I’d stay away from any type of metal. Ceramic or glass containers are best to store your sourdough starter.
4. Largemouth container – it’s nice to have something that has a large mouth so you can easily scoop some of your starter out.
5. Large enough – the exact size is dependent on how much starter you like to keep on hand at any given time. I like to keep at least 4 cups on hand to make things that require a lot of sourdough like my same-day sourdough pizza crust. In any case, make sure the container is big enough to at least double the amount you keep on hand.
6. Have two suitable containers on hand – It’s important to transfer your sourdough starter to a clean container once the current one needs to be washed. Have one ready to go to make the transfer.

Related: How to Store Sourdough Bread

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(These affiliate links help to support this blog at no extra cost to you. Your support means the world to me!)

• Berkey water filter (use this link for a discount)
• Glass jar for sourdough starter
• Kitchen scale
• Banneton baskets
• Dutch oven
• Lame
• Dough scraper
• Stainless baking sheet
• Silicone baking sheet mat
• Grain mill

Some Sourdough Recipes

Roasted Garlic Sourdough Bread

Sourdough Bagel Recipe

Sourdough Tortillas

Sourdough Flatbread

Sourdough Pizza Crust

Pin it for later – How to Revive a Bad Sourdough Starter

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