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. Christa

    So I have just started an all rye starter. I’m on day 3 and she is quite active and looks amazing and bubbly. The only issue is I don’t feel like this new starter smells quite like my unbleached white starter. Is this normal? Could I have a bacteria? I’d rather not find out in a few days when I bake with it for the first time.

    1. Barbara Alpern, post author

      Hi Christa, rye starters do tend to smell a bit more fruity and sour than a white flour starter, so this is not at all unusual. And during the creation phase it’s not uncommon for starters to sometimes smell a little funky, so by all means continue feeding your fledgling rye starter and trust that it’s behaving exactly as it should. If this is a starter that your creating from scratch, it will take about 10 days to develop a fully mature starter.

  2. Donna

    I had a started in plastic with hooch which I mixed in and let it sit. Put it in glass and now no gray hooch just a white powdery bubbly layer on top. Is that mold? Dont really see any other color to it. Should I start over? Sorry so new to this

    1. Barbara Alpern, post author

      Hi Donna, it’s hard to say if what you’re seeing is mold, but I doubt it. Bubbly is usually a good sign, but I’m not so sure about “powdery.” You didn’t mention at what stage of development your starter is, so if it’s still in the creation phase, it will be more prone to unfriendly invasion from mold and bacteria. If it’s a fully developed mature starter and hasn’t been left out of the refrigerator for an extended time without being fed, it’s probably fine. Hooch isn’t really a desirable outcome, but more a sign that your starter is hungry and needs to be fed, so I would recommend feeding it twice daily at room temperature for a few days and see if it recovers. You may want to discard the powdery top portion of the starter as a precaution, and place the starter in a clean container before you begin these recovery feedings.

  3. Mia


    My starter is about 16 days old. When feeding, I stirred it with a metal spoon and then I read that you should only stir with a wooden or plastic spoon otherwise your starter will get a paint-like smell because of the reaction with the metal. That is exactly what happend – a paint-like smell developed with a grey layer on top. I discarded half in an attempt to change the smell, and added flour and water. It still smells like paint. Should I start over?

    1. Barbara Alpern, post author

      Hi Mia, I doubt the odor you describe was caused by stirring your starter with a metal spoon, but regardless of the cause, it sounds like your starter just needs a little TLC to get it out of this funky stage. I would recommend feeding it at room temperature twice daily for a few days. Try feeding it with room temperature water and be sure to discard all but 1/2 cup (4 ounces) starter each time you do a feeding. Feed the 1/2 cup of starter 1/2 cup (4 ounces) water and 1 scant cup (4 ounces) flour. Leave your starter out at room temperature and I’m guessing after a few days of this feeding routine it will be back to smelling mildly tangy and delicious!

  4. MP

    My Rye on day one looks awesome, big bubbles a little rise. As soon as I start adding you Unbleached Flour the starter just goes completely flat. It seems related to your flour. 4 attempts and each time same issue. Add KA Unbleached and it just stops bubbling.

    1. Barbara Alpern, post author

      Hi MP, it’s not uncommon for a lull to occur after the initial burst of activity you see with the whole rye feeding. Try continuing with the rye flour feedings through around day 5, feeding only once daily. Once your starter begins to rise and fall fairly predictably you can switch to using AP flour and begin feeding twice a day.

  5. Bernardo

    My starter is four days old, I’ve fed it at about 12 hour intervals.
    I am using a clear plastic container with a loose rubber lid.
    It does not look at all like the starters you have photographed at the top of the post. Mine “separates” into three layers. A 1-1/2″ thick bottom layer of pretty homogeneous paste with no bubbles. Over it, a very thin 1/4″ middle layer of a clear/yellowish liquid. Over that a 3″ top layer of foamy paste.
    Is this normal?
    I’ve been stirring it at every feeding.

    1. Barbara Alpern, post author

      Hi Bernardo, your starter does sound like it has a unique appearance, but I don’t think anything has drastically gone wrong. What temperature water are you using and how warm is your kitchen? It sounds like after 12 hours your starter is looking a little over-fermented, so it may be helpful to use cooler water (60-70 degrees). Be sure to stir very well each time you feed your starter, discarding all but 4 ounces (1/2 cup) starter. Feed this 4 ounces of starter with 4 ounces (a scant cup) of flour and 4 ounces (1/2 cup) of water.

  6. Denee

    I was on day two of my starters life and getting ready to feed it when I noticed pink all throughout it. I discarded the starter, but I’m wondering what I did wrong?

    1. Barbara Alpern, post author

      Hi Denee, it sounds like your starter must have gotten contaminated in some way. This happened to me once when I was teaching a sourdough class and had a classroom full of students all creating stiff starters. Imagine my embarrassment when my starter was the only one to develop a pink streak! A starter that is still in the creation stage hasn’t developed the same type of defenses that a mature starter possesses, so it’s a little more vulnerable to invasion. You did the right thing to discard your starter. I clean my container and implements with very hot water prior to beginning a new starter, but there’s no need to go crazy and sterilize everything each day. It’s unlikely you’ll experience the same problem the next time you attempt to create a starter, so give it a go and let us know how it turns out!

  7. Jill

    Hi there! I’m just beginning a starter. I’m only two days in. Starting from scratch with flour and water. I have followed the instructions carefully. It’s already super bubbly and puffy. The question I have is the smell. What should it smell like? I’m crazy sensitive to smell so it might just be my paranoid nose, but it smells funky. How can I tell good funky from bad funky? Thank you so much!!

    1. Barbara Alpern, post author

      Hi Jill, I wouldn’t worry too much about funky smells during the first 10 days or so of starter development. Different bacteria create different odors, and it’s not uncommon for your starter to smell quite funky at times during this period. Once your starter is fully mature, however, it should smell mildly tangy and not at all nasty. A mature starter that has been neglected in the refrigerator for an extended time might develop a stronger odor, but a few days of feeding at room temperature twice daily should restore it back to it’s normal activity level and aroma.

    1. The Baker's Hotline

      Not at all Judy! You can either stir it in or pour it out, baker’s choice. Stirring it in will give you a stronger flavor. Annabelle@KAF

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