Is My Sourdough Starter Bad? How to Revive Old Inactive Starter

Is your starter looking “sus”? Are you wondering if it’s still viable and active, or if your sourdough starter has gone bad? If you answered yes to either of these questions, or otherwise have a funky, crusty, neglected old sourdough starter on your hands, then you’ve come to the right place! Read along to learn how to tell if your sourdough starter is still good or not, how to feed and revive an old inactive starter, prevent mold, and other useful tips. I’ll share photos that will help you tell the difference too.

The good news is: sourdough starter is far more resilient and forgiving than you may think!

Sourdough starter care and feeding frequency

“Feeding” a sourdough starter is the act of adding fresh flour and water, which keeps the beneficial bacteria and yeast alive. A portion of the existing starter is usually removed before it’s fed, either to use in a recipe or discarded. To keep sourdough starter healthy, active, and alive, it needs to be fed on a regular basis.

Sourdough starters that are kept out at room temperature may need to be fed as often as daily, or several times per week. If you store your sourdough starter in the refrigerator (like we do) it should be fed once every few weeks. Storing sourdough starter in the fridge is the best way to prevent it from going bad, especially with long periods between feeding. Or, you can dehydrate sourdough starter to keep it alive for extended periods of time (up to a year or longer) without needing to feed it at all. Learn how to reactivate a dry sourdough starter here.

However, life gets busy! I get it. Despite knowing the “best practices”, we often go many months between feeding our starter…. and she’s still plenty alive! We simply follow a modified feeding process (explained below) to revive the starter after months of neglect. Note that our sourdough starter is old and established though. Younger starters may not be so forgiving. So, I don’t necessarily recommend waiting several months to feed your starter. 

Learn more about feeding and maintaining a sourdough starter here.

How do you know if sourdough starter has spoiled or gone bad?

The main indicator if a sourdough starter is still good or not is if it will still rise and fall after feeding it fresh flour and water. If it does, it’s still alive! Yet old neglected sourdough starters are sluggish and need additional time and help to become fully active again, which we’ll explore more in the “reviving an old sourdough starter” section below.  

If your sourdough starter is obviously moldy, then unfortunately the starter has gone bad and should no longer be used. Mold on sourdough starter will look raised and fuzzy, and can range in color from white, yellow, green, blue or pink spots. It will often grow on the sides of the storage container as well as on top of the starter itself. 

That good news is, mold isn’t all that common on sourdough starter! (Especially on an established one). The beneficial bacteria and yeast in the starter create acidic conditions that help to naturally preserve it and ward off mold. That’s not to say an old neglected sourdough starter doesn’t look and smell pretty funky though! But more often than not, it’s still alive and okay to use. If you’re experiencing mold issues, check out the tips about preventing mold on sourdough starter at the end of this article.

Normal characteristics of an unfed, neglected sourdough starter

When a sourdough starter hasn’t been maintained or fed in a while, it will develop a layer of dark liquid called hooch. Hooch is an acidic alcohol-like byproduct of fermentation. It may be brownish, blackish, or evenly slightly pinkish purple. While it’s totally harmless, it’s a sure sign that your starter is hungry!

Sometimes there are white spots or lumps on the surface of the starter itself but below the layer of hooch, likely where air bubbles once were (not to be confused with mold – see photo below). Old starters will also smell very strong and acidic – like vinegar, acetone, or even nail polish remover. After many months of neglect, the storage container usually looks pretty crusty and sketchy too. All of this is normal, and the starter is still okay to use and revive. 

On the other hand, if it smells rotten, gross, putrid or otherwise unusual (not acidic) the sourdough starter is likely spoiled and should be discarded.

If your sourdough starter has gone bad, you can either get a new starter from a friend, learn to make one from scratch here, or buy an organic sourdough starter from our shop – which is basically foolproof!

How to Revive an Old Inactive Sourdough Starter

Reviving an old neglected sourdough starter is similar to feeding a starter under normal circumstances, with a couple of exceptions. The trick is to be patient and not feed it too frequently at first. The starter needs more time to slowly rebuild the population of starved microbes inside. It may also take additional feedings to get as fully active as it once was.

The biggest mistake people make when trying to revive an old inactive sourdough starter is to repetitively feed it (e.g. several times per day) in an attempt to wake it up. Doing this can be counterproductive and inadvertently remove more and more of your microbe colony before they’ve had a chance to feed and multiply, resulting in a weaker starter. 

Instructions

1. Warm up. Assuming your starter has been stored in the refrigerator, take it out and let it warm to room temperature for several hours (or overnight) before proceeding.
   
   
2. Dump off the hooch. When a starter develops a little hooch a week or two after feeding, you can either stir it back in or dump it off. Keeping the hooch is actually one way to make your sourdough bread taste more sour, if that’s what you’re after! Yet it’s best to remove the hooch when reviving an old sourdough starter that hasn’t been fed in a month or longer. 
   
   
3. Use a clean container. Give your starter a fresh, clean home! We transfer some of our old starter into a second flip-top container before feeding it. If you don’t have a spare container, then temporarily transfer your starter into a clean bowl while you wash the other.
   
   
4. Discard. You only need ½ cup of starter for the next step. So, you can either discard some or put the extra into a different storage container to keep if you wish.  *If the sides of your storage container look like it may have mold on it, but not the starter itself, try to carefully scoop out the starter without touching the sides of the container.

5. Feed. In a fresh clean container, combine ½ cup sourdough starter, ½ cup lukewarm filtered water, and a scant (light) cup of flour. If you prefer to feed your starter by weight, use equal weights of starter, flour and water (e.g. 100 grams of each). Stir well. Note the starting level on the container so you can track its growth.
   
   
6. Place the starter in a warm location. Sourdough starter is most happy and active around 70-75°F. This can be a challenge during winter in most homes, but do your best to find a cozy spot. For example, we find the under-cabinet lights in our kitchen make the shelf directly above them nice and warm.  

7. WAIT. Now is the time to put on your patient pants! A well-maintained, regularly-fed starter will start to rise within just a couple hours of feeding it. However, an old neglected sourdough starter can take 24 hours or longer to show signs of life. So, wait at least 24 hours to feed it again. (That is, unless it rises and falls all the way back down to the starting point sooner – then go ahead and feed it again.)

8. Discard and feed again. Next, stir the starter and remove all but about half a cup. We honestly don’t measure so we likely keep a tad more than that, but leave behind about an inch in the bottom of our container. Now repeat Step 5: add ½ cup lukewarm water and a scant cup of flour, mix well, and put the starter back in a warm place. You don’t need to necessarily wait 24 hours to feed it again this time. The starter will tell you when it’s ready – once it rises and falls again.
   
   
9. Repeat a third feeding if needed, especially before baking bread. Once the old starter has been thoroughly reactivated, it will reach peak activity (rise to at least double in size) faster and more vigorously than when it first came out of the fridge. 

Troubleshooting Tips

Sourdough starter still not rising? These tips may help:

• To revive your old sourdough starter (or make starter more active), try feeding it with half regular flour (bread flour or all-purpose) and half wheat or rye flour. Rye seems to make sourdough starter especially bubbly!
  
  
• Your starter may be cold. Use a thermometer to monitor the temperature where the starter is stored. If it’s below 65°F, get creative to find a warmer location or provide additional heat (70-75°F). One option is to use a small seedling heat mat or other heating pad nearby (but not directly on the starter – you don’t want to make it too hot). Another option is to turn the oven light on, place the starter inside near the light, but keep the oven OFF. It creates a nice warm little box.
  
  
• A runny or thin sourdough starter will bubble but not rise as well. Or, it will rise slightly but fall back down very quickly. Aim for a consistency similar to very thick pancake batter. If your starter container is tipped sideways, the starter should slowly move and ooze – but not immediately pour right out of the container. So, if your starter seems too runny, thicken or “stiffen” it up by adding more flour. Add a couple tablespoons at a time, stirring and adjusting as needed. 

Why did my sourdough starter get moldy?

Mold on sourdough starter is most common with young or brand new starters. The new colony of bacteria and yeast aren’t yet established enough to keep the mold at bay. Then when faced with unfavorable conditions (such as a cold kitchen, infrequent feeding, or a less-than-clean storage container) mold is more likely to take over. Therefore, do your best to follow recommended best practices to feed and maintain your starter to keep it happy – especially at first. 

Mold is even more common when attempting to make a new sourdough starter from scratch. It’s definitely possible, but is notoriously more tricky (and moldy) than starting with an established culture. That’s actually what motivated us to sell sourdough starter on this site! We began our sourdough journey with a homemade starter, and then taught others how to make one from scratch in this tutorial. While the process works for some folks, others would reach out in frustration as their starter grew mold time after time. So, we decided to offer organic dehydrated sourdough starter (a little piece of our own) to help give folks an easy jump start!

It’s also possible for an established sourdough starter to mold. For instance, if the storage container or utensil it was stirred with was somehow contaminated with mold spores. One way to avoid mold contamination is to protect and store your starter in a thoroughly cleaned and sealed container, such as a glass flip-top container like this. (Don’t worry, the seal isn’t SO tight that the gasses can’t escape). Finally, an established starter may grow mold if it goes unfed for so long that the beneficial microbes starve and die off completely. 

My sourdough starter is active! Now what?

Congratulations! Now, you can either use your active starter to bake something delicious, or you can simply put it back in the refrigerator for storage. Going forward, try to feed your starter once every few weeks instead of waiting many months. It shouldn’t be that hard to do if you plan to bake on occasion! We only bake a couple times per month, so our starter gets fed then – when we are activating it to use in a recipe.

Most sourdough bread recipes call for starter at “peak” activity: when it’s been fed and fully rises, but just before it starts to fall back down again. For instance, we call for active starter in our no-knead sourdough bread, simple focaccia, cornbread, or pizza dough recipes. On the other hand, you can use either active starter OR discard (unfed) starter in many recipes too – including our sourdough crackers, pancakes, and ginger molasses cookies. Enjoy!

And that is how to revive an old inactive sourdough starter.

I hope you can see that sourdough starter can be pretty darn forgiving and flexible! That’s not to say we should intentionally neglect the poor things, but again, it happens. I also hope this article gave you the insight to tell if your sourdough starter is still good or not, and confidence to proceed even if it looks a bit sketchy. So go ahead and feed that old hungry starter, so you can feed yourself some delicious homemade bread! Please let us know if you have any questions in the comments below. Thank you for tuning in!

Don’t miss these delectable recipes:

• Basic No-Knead Sourdough Bread Recipe
• Simple Sourdough Focaccia Recipe
• Sourdough Starter Feeding & Maintenance Guide
• Sourdough Pancakes recipe (discard or active starter)
• Herb and Whole Wheat Sourdough Crackers (discard or active starter)
• Sourdough Cornbread
• Cinnamon Spiced Sourdough Chocolate Chip Cookies
• Soft & Chewy Sourdough Ginger Molasses Cookies