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. Keith B. Hammond

    Patience is a virtue, but one I sadly lack. I’m now on Day 7 and my starter has just a few bubbles on top but I’ve seen no evidence of expansion. I used whole wheat flour on Day 1 as recommended. I’ve followed the recipe exactly and my hydration seems OK. I weigh everything on a digital scale. On Day 6 I decided to experiment. I split my starter into thirds (4 oz each). To one I added 4 oz of unbleached APF + 4 oz water. To the second I added 4 oz of whole wheat flour +water and to the second I added 4 oz of KA Rye (not the Pumpernickel). I fed the first 12 hours later with APF and the other two their respective flours. Then this morning I fed each of them with APF., Five hours later there are a few bubbles on the original (seven to be exact), three on the whole wheat and one on the rye. I was hoping for more and that I would get a boost from adding either whole wheat or rye. Am I being too impatient? I also freeze my flours, except the APF which I use frequently enough to keep at room temperature. Instant yeast stores well in the freezer, so I would assume any natural yeast would also remain viable. Am I correct? I’m using filtered cold water from the refrigerator and warming it to 90 – 100 degrees F in the microwave oven. Any suggestions?

    1. Barbara Alpern, post author

      Hi Keith, patience usually does pay off when it comes to sourdough starters, but I’m surprised that you didn’t see more activity with the whole wheat and rye versions of your starter experiment. It’s possible that a few more days of feeding with the whole grain flours would yield more vigorous results. In addition, I’m a little concerned that the temperature of your liquid could be causing issues. When you heat up water in the microwave there can be hot spots that are higher in temperature, and yeast will die at 145 degrees. You might want to try leaving a jug of water out at room temperature for feeding your starter, rather than heating the water in this way. If you do use the microwave to heat your water, be sure to stir it well before checking the temperature, and then aim for water in the 75-80 degree range unless your house is very cool. I wouldn’t recommend using water over 90 degree. Freezing the flour shouldn’t cause any issues, but I would allow your flour to come to room temperature before you use it to feed your starter. For more help troubleshooting your sourdough starter please give our Baker’s Hotline a call at 855-371-2253.

  2. Bonnie Raines

    I’m a beginner at creating my sourdough starter. I’ve been feeding it about once a day for 2 weeks. It bubbles and smells yeasty and tangy (as I would expect), but it is not doubling in volume. I follow the King Arthur method of scoop and sweep for my flour to hopefully have more accurate measurements, but I’m not sure what else to try. What should the texture be like? By each morning when I check it, it seems very liquid. Is this right? Thanks in advance!

    1. Barbara Alpern, post author

      Hi Bonnie, it would be helpful to know what size container you’re storing your starter in, since a starter that’s stored in a wide bowl will have a harder time displaying the “doubles in size” behavior than a starter stored in a jar that is taller than it is wide. In addition, if you’re not around during the day to observe your starter, it’s possible that it’s rising and falling while you’re away. If you don’t have our sourdough crock, try storing your starter in a one quart wide mouth canning jar and see if you’re able to discern more of a rise after feeding. When measuring your flour we recommend this method, which isn’t quite the scoop and sweep method you describe. And remember that the starter recipe calls for feeding a “scant” cup of flour, so one that isn’t quite full. That being said, it doesn’t sound like the consistency of your starter is too far from the mark. When you first feed your starter it should be a pasty, but easily stirrable consistency. As it ferments it develops bubbles throughout and becomes much lighter and airier in texture–more like a thick pancake batter. At the end of the cycle, after the starter has risen and fallen, it will be much thinner in texture, and may have small or frothy bubbles on the surface. If you determine your starter isn’t rising after changing containers, try switching to feeding with either whole wheat or whole rye flour for a few days and see if this gets your starter rising. Once you observe your starter rising and falling in a predictable manner, you can switch to feeding with unbleached all-purpose flour twice daily. When your starter is rising and falling nicely with the all-purpose flour, then you should be good to go!

  3. Hilary Mac Austin

    I only bake a loaf of bread about once a week or even every two weeks. In order not to waste too much flour I put the starter in the fridge between uses. I let it sit out for up to a day before I use it. Then I feed the starter and let it sit out for about a day before I put it in the fridge again. Is this okay?

    1. Barbara Alpern, post author

      Hi Hilary, it’s fine to keep your starter in the refrigerator when you’re not baking, but it will get a little sluggish when stored there. Typically a day or two of twice a day room temperature feedings is helpful to bring your starter back to full vitality before baking. This is particularly important if you’re planning to bake a naturally leavened recipe that depends on the starter for both flavor and rise. I would recommend feeding your starter right from the refrigerator, rather than letting it sit out for an extended time without feeding it. It will warm up gradually as it ferments and won’t suffer from the cooler starter temperature. On the other end, when you’re returning your starter to the refrigerator, I would recommend feeding it and then letting it sit out at room temperature for 2-4 hours before putting it back in the fridge. You want to see that the starter is showing signs of fermentation (bubbles) before you put it in the refrigerator, but letting it sit out all day may not be ideal.

  4. Minke

    Hey, I’m a sourdough newbie and I have a suspicious situation. The thing is; the recipe said that I needed to combine whole wheat flower and water and let this rest for 12 hours. Since there wasn’t any bubbling going on after 12 hours, I let it rest another 12: 24 hours in total. Then the sourdough had doubled in size and I discarded all but 113 grams. I feeded it 113 grams of all purpose flour and water and then let it rest for 12 hours. However I checked after 4 hours and it had already doubled in size! Because the pot it was in was getting too small I wanted to devide it, but performed a floating test, just to see what happened. Well, the starter floated!
    My question is; the sourdough cannot be ready in 2,5 – 3 days right? That’s way too quick! It was in quite a warm place, but still. Shall I keep feeding it every 12 hours until it is around 7 days old? Shall I put it in maintenance mode? Or can I bake some bread with this young starter? Thanks in advance!

    1. Barbara Alpern, post author

      Hi Minke, it’s not unusual to see a significant rise early on in the process, but this doesn’t mean that your starter is ready for baking! There are some strains of bacteria that can produce carbon dioxide and cause the starter to rise, but this isn’t the kind of rise we’re looking for. I would recommend continuing to feed twice daily at least through day 7. You may actually observe a lull in activity and very little rise for a few days, but eventually your starter will begin to rise and fall predictably within a 12 hour period. Once you see this happening, you can begin baking with your starter, but I would recommend continuing to feed it at room temperature twice daily for a few more days for full flavor development. If your starter experiences a lull in activity that lasts for several days, let us know and we can suggest some tactics you can try to help encourage the wild yeast to kick in.

  5. Jacinta Gill

    Hey there first time starter here! And I’m abit lost it smells abit yeasty but also abit bad there’s hooch on it only a little though it has some of the starter floating on top what do I do? Do i mix it all back in and do the feeding process? Do i remove the floating layer and the hooch and then feed it?? its 4 days old so a baby any advice????????

    1. Barbara Alpern, post author

      Hi Jacinta, as long as you’re not seeing any pink or orange hue and no signs of mold, it’s fine to stir everything together and continue feeding as usual. It’s not unusual for the starter to smell a little off at times during this initial creation phase, so don’t worry about the odor at this point.

  6. Patricia Rose

    I made my starter last Saturday. I have been feeding it every 24 hours and it has been looking great and bubbling pretty well until this morning when I looked there were no bubbles at all and about 1/2 inch of liquid on top. I kept it in a warm place the whole time. Is it salvageable?

    1. Barbara Alpern, post author

      Hi Patricia, I replied to this question in Part 2. Here is that reply:

      I’m not sure what temperature you’re storing your starter at, but there’s no need for it to be stored in temperatures higher than 80 degrees, and higher temperatures may cause it to ferment too quickly. It sounds like your starter might benefit from a little change in its feeding routine. I would try switching to feeding with whole wheat flour or whole rye flour and saving 4 ounces of starter and feeding it 2 ounces of flour and 2 ounces of water. Feed once daily with the 4:2:2 recipe. I’m guessing within a few days you’ll see the starter begin to rise and fall fairly predictably. Once you see this rising and falling, you can switch back to feeding with the 4:4:4 recipe and unbleached all-purpose flour, and begin feeding twice daily. Once you’re starter is rising and falling with the all-purpose flour feedings and has a mildly tangy aroma, then you should be ready for baking!

  7. Erin Cox

    I am currently on day (almost) 5 of creating a new starter. I’m afraid I might have screwed it up on day 3. On day 2 it rose quite well and then collapsed a bit. I did the day 3 feeding and then decided to divide it into two containers, in case it rose again. However, it has not increased in volume since the first time it did. It is bubbly on the top, but basically smells like flour and water…possibly a bit fermented, but I could just be hopeful.


    1. The Baker's Hotline

      If you continue to feed your starter using the method recommended here — discarding all but 4 ounces then adding 4 ounces of flour and 4 ounces of water — you should start to see your starter rise and fall regularly within a few hours of feeding. If you see bubbles and smell a slightly tangy aroma, that’s a sign that your starter is alive! Keep feeding it regularly, storing the starter at room temperature between feedings until it doubles in volume after feedings. Fingers crossed! Kye@KAF

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