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. Joanne

    Hi, I’ve recently made a new batch of starter and it started to have this really sour smell and some white spots on the 4th day. Does it indicate that the starter has gone bad? Room temperature is around 30°C with high humidity. Should I use room temperature water instead of warm (42°C)? Thanks!

    1. Barbara Alpern, post author

      Hi Joanne, while the sour smell isn’t necessarily a bad sign, the white spots could be mold, so I would recommend starting over and cleaning all your utensils and jar very well with boiling water, if possible, before beginning a new starter. Since your room temperature is so warm, you can definitely use cooler water to feed it (15-21 degrees Celsius). This may help slow down fermentation and (hopefully) prevent the starter from spoiling in future attempts.

  2. Charles Guttilla

    Barbara, I have been baking with SD for 9-10 years. All of a sudden my starter took on an orange color and unusual smell. I tossed it immediately and started anew. After using the new starter for several bakes, I fed it and placed it into the fridge. It was in the fridge for maybe 2 weeks when I took it out today to begin feeding for baking on Saturday. It was awful. Black mold on sides of container; a hard layer of orange on the top along with a bit of black mold. Starting another starter this time, but what in the world could cause such drastic contamination like this in such a short time?

    1. Barbara Alpern, post author

      Hi Charles, it does seem unusual that your starter would spoil so drastically when refrigerated for only two weeks! When you created your new starter how long did you feed it before beginning to bake with it? I wonder if your starter was fully mature, or if it might have needed more time to develop. It generally takes at least 10 days to cultivate a fully mature sourdough starter, and sometimes longer, depending on how your starter responds to the process. A starter that is still in the creation phase is less resistant to mold and unfriendly bacteria, so this could explain its rapid decline. You might also want to check your refrigerator temperature and be sure that it’s not over 38 degrees. If your refrigerator is getting into an unsafe temperature zone, and you cover your stater loosely, it may be exposed to more mold and bacteria than it would normally come across. Even if the starter is covered well, a warmer refrigerator temperature could cause it to spoil more quickly. When you begin your new starter I would consider using Debra Wink’s Pineapple Juice Solution to start and then shift into the equal parts flour:water:starter and feeding twice a day with all-purpose flour once the starter is rising predictably. Once the starter adjusts to the AP flour and the new routine and is rising predictably, then you should be good to go. Especially in warmer weather your mature starter will generally need to be fed twice daily at room temperature, and at least once a week when stored in the refrigerator. And be sure to clean all your utensils and containers very well with hot/boiling water if possible before launching into a new starter.

    1. Barbara Alpern, post author

      Hi Vonnie, this blog post gives you all the information you need to bring your dried starter back to life.

  3. Jutika Kakoti

    I have a doubt of how much tanginess is good for sour dough bread. I am living in North eastern part of India, i e Assam. Here humidity is very high i summers with temperature frm 28 °C to 38°C with 70-80%humilty in air. Last year i made my sourdough which turn bad.

    1. Barbara Alpern, post author

      Hi Jutika, while I’ve never worked with sourdough in such a warm environment, I can imagine that it’s difficult to keep up with the rate of fermentation, and your starter will be likely to spoil if left unfed for an extended time at room temperature. My strategy would be to use very cool water and flour to feed the starter, and to use a lower percentage of starter as compared to flour and water in order to further slow down fermentation. For example, you may want to alter the ratio of starter from 1:1:1 (or equal parts starter, flour and water by weight) to something more like 1:2:2 or even 1:3:3. This may be tricky to do during the creation stage, but it should work well once you’re maintaining your mature starter. You can also make use of the refrigerator and place the starter in there when you’re not able to feed it promptly at room temperature, or when you’re not baking daily. Generally feeding the mature starter at least once a week when stored in the refrigerator is helpful. Give it time to start bubbling at room temperature before you refrigerate, and expect that it will need a few feedings at room temperature post refrigeration to recharge the populations of wild yeast and friendly bacteria prior to baking. For more information on this subject I would encourage you to check out this conversation on The Fresh Loaf and also this one.

  4. Joyce DeWitt

    Can I make a new starter with the disguarded sourdough starter.
    Question 2
    I fed my starter with bread flour the first two feedings did I ruin it

    1. Barbara Alpern, post author

      Hi Joyce, yes, you can certainly make another starter with your discard, although I wouldn’t encourage too much expansion in this way, or you may find yourself tending more starter babies than you know what to do with. If you need more starter for your baking than you normally maintain, you can always build the quantity as you feed the starter leading up to baking, so it’s simpler, more efficient and cost effective to tend to one starter rather than several. On the other hand, if your friend is begging you for a starter just like yours, by all means, share the wealth! As far as feeding your starter with bread flour goes, this certainly won’t ruin it, but unbleached all-purpose flour will provide a better meal because it’s higher in starch, and starch is what provides nourishment for your starter.

    2. Joyce DeWitt

      Hi Barb
      Thank you
      Yes it can get out of hand. I had to release some my starters.
      Giving some away to friends. I also try to bake with the disguared starters in biscuits and today I’m baking pretzels from the recipe here for my grandkids.


    3. Barbara Alpern, post author

      Sounds like you’ve found a good groove for using your discard and are becoming quite the sourdough baker! Congratulations, and let us know if you run into more questions along the way.

  5. Anne

    The guide included with the sourdough starter says the ‘discard’ will keep for a week in the refrigerator. When I fed my starter last week, I also fed the ‘discard’ and placed back in the ‘fridge for a week. It smells a little more ‘alcohol’ than the one stored in the crock. Is it safe to use if over a week old, especially if I fed it when I separated the ‘discard’ from the crock?

    1. Barbara Alpern, post author

      Hi Anne, the discarded starter doesn’t go “bad” very quickly in the refrigerator, so I wouldn’t worry about the safety of using it if it’s a little past the week mark, but the flavor will change over time and it can taste a little funky if it’s been in the fridge too long. It sounds like your discard is just fine to use!

  6. Cynthia Speed

    Hello, I have a nice ripe starter now. I noted that you can save unfed discarded portions to use later. Can you tell me, please, the best way to save the discard. In a covered bowl in the frig, as in a lidded Tupperware container or is a loosely covered container? Thanks a big bunc

    1. Barbara Alpern, post author

      Hi Cynthia, we recommend storing your sourdough discard in a separate container in the refrigerator and trying to use it within a week. As long as the container has sufficient “head room” above the starter for fermentation gases to accumulate, it shouldn’t cause any problems to put the lid on tight. You can also open the lid now and then to vent the gases. The reason we say that the starter should be “covered loosely” is that fermentation gases can build up in a tightly lidded container and cause the lid to pop off.

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