Sourdough starter troubleshooting: What does it take to kill your starter?

“Did I kill my starter?” This is a surprisingly common sourdough question on our Baker’s Hotline. Novice and experienced bakers alike worry about the viability of their starters and call us for sourdough starter troubleshooting advice.

For many sourdough bakers, the underlying biochemistry at work in their starter remains a bit of a mystery. Thankfully, it’s quite possible to bake great sourdough bread while still being a little fuzzy when it comes to what’s actually happening in that little jar of starter.

The 6 to 10 days it takes to create a healthy and mature sourdough starter from scratch requires slightly more attention to “death threats,” because a fledgling starter hasn’t yet developed the defenses that characterize a mature starter. But once your starter is fully developed, it’s really pretty darn hard to kill.

And if you’ve purchased a sourdough starter from us, rest assured that it’s a mature specimen that will stand up well against unwanted bacteria or mold.

Sourdough Starter Troubleshooting via @kingarthurflour

Things that WON’T kill your sourdough starter

METAL: Stirring your starter with a metal spoon or placing it in a metal bowl won’t kill your starter. While we don’t recommend making or keeping your starter in contact with reactive metals like copper or aluminum, stainless steel is harmless. Sourdough Starter Troubleshooting via @kingarthurflourMILD NEGLECT: Missing a feeding or not timing the feedings exactly 12 hours apart won’t even come close to killing your starter. Please don’t ever set your alarm to get up in the middle of the night to feed your starter!

INCORRECT FEEDINGS: Feeding your starter the wrong amount of flour or water won’t kill it. While your starter may seem too dry or too wet, and may not rise the way you expect, no permanent damage has been done. You can correct its consistency by adding a little more flour or water, and then being more careful the next time you feed it.

BRIEFLY FREEZING YOUR STARTER: While there’s some dispute among sourdough enthusiasts about the benefits and/or dangers of freezing sourdough starter, a brief period in the freezer isn’t likely to kill a fully developed starter.

I recently froze a portion of my well-maintained starter a few hours after it was fed. Three days later I thawed it out at room temperature and let it continue to ferment. It was definitely sluggish at first, but after a second feeding it rose well and had a good aroma.

That being said, too much time in the freezer will definitely damage some of the wild yeast in your starter, and is also likely to kill off some of the friendly bacteria that contribute flavor. If you need to put your starter on hold for an extended time, we recommend drying your starter.

What does it take to kill a sourdough starter? When is it time to give up and start over? Click To Tweet

Things that WILL kill your sourdough starter

HEAT: If you allow your sourdough starter to ferment in the oven with the light on to keep it warm, and then forget it’s in there and turn on the oven, it’s unlikely your starter will make it out alive. Yeast dies at 140°F, and it’s likely that your sourdough starter will suffer at temperatures even lower than that. It’s best to maintain your starter at comfortable room temperature (around 70°F), though a little higher or lower won’t hurt anything.

SEVERE NEGLECT: If you neglect your starter long enough, it will develop mold or signs of being overtaken by bad bacteria. Mold can appear in various colors and is typically fuzzy in appearance. Bad bacteria is generally indicated by an orange or pink tinge or streak. Once your starter has lost its natural ability to ward off intruders, it’s time to start over.

Sourdough Starter Troubleshooting via @kingarthurflour

How to tell if your starter has gone bad

“Hooch” is the liquid that collects on the top of your starter when it hasn’t been fed in awhile. This liquid is the alcohol given off as wild yeast ferments. The presence of hooch isn’t a sign that your starter is in danger. However, it does indicate that your starter is hungry and needs to be fed.

When your starter is neglected for an extended period, the hooch tends to turn from clear to dark-colored. We get lots of calls from sourdough bakers worried about the safety or danger of various hooch hues. Is gray bad? What about brown or black? Surprisingly, none of these colors indicate that your starter has spoiled.

Sourdough-Starter-Troubleshooting via @kingarthurflour

See the orange streak? This starter shouldn’t be saved.

However, if you see a pink or orange tint or streak, this is a sure sign that your sourdough starter has gone bad and should be discarded. The stiff starter above was left out at room temperature for two weeks. It’s definitely time to throw it out and start over.

Sourdough starter troubleshooting: points to remember

1. Well-maintained mature sourdough starters are extremely hardy and resistant to invaders. It’s pretty darn hard to kill them.
2. Throw out your starter and start over if it shows visible signs of mold, or an orange or pink tint/streak.

I hope you’ll share your own sourdough starter questions and discoveries below. There’s always more to learn when it comes to sourdough!

And please check out part 2 of this sourdough starter troubleshooting post!

Barbara Alpern

Long time professional artisan bread baker, caramel maker and member of our Baker Specialist team, Barb grew up in Ann Arbor, Michigan and has four grown sons. She has baked in Michigan, Maine, Vermont, and Texas (if you count baking cookies for her son's wedding!).


  1. Eric

    I’m on my second attempt now at making sourdough starter using the KAF recipe.

    My first one I threw out because it developed an incredibly powerful and unpleasant stench. It made me and my wife gag to smell it. On days 2 and 3, it had a pleasant, fruity smell; but on day 4, it suddenly became this horrible stink.

    The second one did the same thing, but this time I kept on feeding it. Over the next few days after the stench developed, it turned into an incredibly powerful and biting sour smell. I figured this was progress, so I kept going. But it’s now been close to two weeks and the starter still isn’t bubbly, nor is it rising. There are maybe a handful of large bubbles on the surface, but that’s it.

    Reading others’ experience, it’s common for the starter to be strong for the first few days, but then kind of die down around day four, sometimes for many days. But that’s not been my experience. My starter NEVER rose. It NEVER had more than a few bubbles. And the smell is not fruity, not cheesy, nor yeasty. I would not describe it as pleasant, either, it just no longer smells horrible.

    About the only thing that seems to be working right is that even though the mixture is very thick and doughy right after feeding, after a few hours it’s very thin and watery. It’s about the consistency of frosting, actually.

    I can’t imagine what I could be doing wrong. The recipe is extremely simple. But at the same time, I’ve been feeding this thing for two weeks now and it hasn’t demonstrated the slightest bit of progress.

    1. Barbara Alpern, post author

      Hi Eric, in order to troubleshoot your starter issue more effectively the best approach may be for you to give the Baker’s Hotline a call (855-371-2253). That way we can discuss some of the variables (type of flour, method of measuring, water source, temperature of environment, and container size) in order to (hopefully!) determine the cause of your starter difficulties. We’re here M-F from 8am-9pm EST, and from 8am-5pm EST on weekends. I can’t guarantee we can solve the problem, but we’d love to talk sourdough with you and try to help!

  2. Bruce

    So I have had my starter going for about 6 months now. The past month or so my starter has had am orange-ish tint to it… but I kept using it. Then this week before I made my loaf the top was covered in mold. I normally only feed my starter once a week and keep it on a shelf. Since it has been winter and its now warming up I think the rising temp is causing this problem. So I dumped out the mold and saved a little of the starter from the bottom, and my starter appears to be fine its rising well and all. But it smells like paint thinner sooo bad. Should I discard it and start over? or should I try the feeding twice a day until its better? also is it still safe to eat, due to it having mold in it? (I hope so bc I have eaten half the loaf so far lol)

    1. Barbara Alpern, post author

      Hi Bruce, I’m a little worried about the orange tint (which could be a sign of unfriendly bacteria) as well as the mold. Both of these are signs that your starter has been neglected to a point where it no longer has the strength to fight off unwelcome invaders. A starter that has been so weakened is going to take quite a lot of time to rejuvenate, so it may be wiser and safer to start over and create a new starter from scratch or purchase a mature starter from us. I doubt that eating the baked bread from your starter will make you sick, but you may know better than I do at this point! With your new starter I would work towards a maintenance routine that involves feeding twice daily when you keep your starter at room temperature, and at least once a week when you store it in the refrigerator. Feeding your starter regularly and often at room temperature will help to build healthy populations of wild yeast and friendly bacteria. I find that a combination of a few days of refrigeration coupled with a few days of twice a day feedings at room temperature prior to baking works well. If you adopt this sort of feeding routine, you’ll have a starter that is both resistant to invaders and able to perform at its best in your baking.

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