The Fresh Loaf

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Sourdough starter smelling like acetone

christiank's picture

Sourdough starter smelling like acetone


I have a sourdough starter that is about three weeks old. I am currently feeding it every 12 hours with a mix of 1:3:3.

The flours I am using a 70% AP (unbleached) 20% Whole wheat and 10% Rye.

The starter smells strongly of acetone.

There are small bubbles forming in the cup where it lives and a small lift at around the time I refresh the starter.

I've baked some breads with the starter but they seem "off" to me.

Can I do something to improve the starter?



greentiger87's picture

I'm a fellow newbie. I've had some incredible, unexpected successes after just two weeks, and some common problems as well. I ran into the acetone problem in the first few days as well, and my reading suggested this is really common and has a few potential (known) causes:

1) Not feeding often enough - But 12 hours seems to be standard. I was feeding every 24 hours when I had the problem, and feeding every 12 hours made the problem vanish.

2) Refreshment ratio - Keeping too much of the starter when feeding is the main issue, but your 1:3:3 is already lower than most.

3) Hydration - In general, the more liquid the culture, the faster the population will outstrip the available food. 

4) Temperature - The higher the temperature, the faster the microorganisms will reproduce and the faster the population will outstrip the available food.

5) The hetero-fermentative lactic acid bacteria and maltose negative yeasts have not yet dominated your culture.

                        a) Some people say just give it time, but three weeks is long enough for that smell to go away, given other people's experiences

                         b) Slightly acidifying the culture for a few cycles can shift the population to what you want, especially if your tap water is very alkaline. I used unbuffered ascorbic acid powder at first, and later on lemon juice. I've read of people using apple cider vinegar or citric acid. I guesstimated the amounts. This in combination with 12-hour feedings trasnformed a culture that almost knocked me out into one that was delightful smelling. Debra Wink originated the "pineapple juice" method, which you can find easily with a search - it's a more concrete, step by step method. 

What does your culture look like at 6 hours? Is it bubbly? What does it smell like?

Good luck :)

ars pistorica's picture
ars pistorica

Hello, I would recommend changing the nature of the starter in a way that might better suit your needs.  Your culture is likely not the problem, but the way you are maintaining it is.  Try lowering the hydration, increasing overall whole-grain content, and only feeding once a day.  Do not chemically acidify your dough.  It is irrelevant to maintaining a good starter, and can work in ways to inhibit your culture in an undesirable fashion.

Try keeping all your starter in as whole a grain as possible.  Rye or whole wheat work best.  One-step stone-ground milling offers the best results.

Lower the hydration to between 50 - 75%.  Find what works best for you.  Most home bakers tend to prefer something closer to the latter value.

Decrease your inoculation percentage to between 5 - 10% (flour to flour basis), which will roughly correspond with a 24-hour feeding-cycle.

Use the same temperature-profile every day.  Room temperature works best.

 I hope this could be of help.

christiank's picture

Thanks for the ideas! I'll give them a try :D

christiank's picture

Actually, I have one other question: When would I revert to the 12 hour feeding schedule?

Should I do that when the starter consistently doubles within the feeding cycle?


ars pistorica's picture
ars pistorica

No, use a 24-hour feeding-cycle for your starter.  Use higher inoculation amounts (10 - 20%) when building your leaven, which will double in less time.

cranbo's picture

are you feeding 1:3:3 by volume or 1:3:3 by weight? there's a big difference between the two; the former is ~170% hydration, the latter is 100% hydration. 

As ars pistorica recommended, lower hydration levels for your starter should help. 

christiank's picture

I measure everything by weight.  After 12 hours the starter started smelling like acetone again, but I'll keep feeding it. 

Is this behaviour normal? Back home I have a starter that is as predictable as a clock. This one (started by my mother in law) is acting in a (for me) very strange way. 

Debra Wink's picture
Debra Wink

Hi christiank,

From what you've told us so far---the unpleasant smell, and "there are small bubbles forming in the cup where it lives and a small lift at around the time I refresh the starter," I suspect that the yeast haven't activated yet (if they had, you would be seeing a real rise). If this is the case, the 12-hour 1:3:3 feedings are keeping them from activating. Give the last feeding an extra day to ferment (just stir and scrape down the sides at feeding time), then drop back to 2:1:1 feedings with your flour mix just once a day until you see real lift-off. When it starts rising you can return to your twice-daily 1:3:3 feedings and the odor will clear.

Best wishes,

LisaE's picture

Hi Christian,

My starter smelled like paint thinner, it was about 2 weeks old. I found the temp was too high and if I left it unfed for 12 hours, it grew mold, not that that is what yours is doing, just sharing my experience.

I decided to try a little orange juice during a feeding or two. I added a tsp of orange juice for 2 feedings (take a tsp out of the amount of water you'd add so the total liquid is the same, just part of it orange juice) the acetone smell disappeared immediately. Another funny thing, I started keeping it in a jar that previously had pickles, I smelled a lot of that instead of the acetone smell...ha ha, it smelled better even if it was only mental! Try a tidge of fresh squeezed OJ or some pinapple juice, the starter is on its way, but it might help give it a kickstart!


christiank's picture

Thanks again for the suggestions! I am now keeping the starter on a 2:1:1 schedule as suggested by "Debra Wink".

I have one last question: How come the starter smells of acetone when (if) the yeasts have not activated? I was of the impression that the acetone smell comes from the starter when the nutriens have been exhausted? The way I fed the starter that shouldn't be the case.

Debra Wink's picture
Debra Wink

If it's not really sourdough yet, it's hard to say what organism is producing the off smell or why. But I agree with you, nutrient exhaustion is highly unlikely with the amounts you were feeding the starter. If you feed it less, the pH will drop and things can progress.

placebo's picture

I had a starter with the same problem as yours. Like you, I doubt it was due to the food being used up. In my case, the yeast had activated. The starter was expanding nicely, but it was still producing an intense acetone/paint-thinner smell. Despite a couple of feeding cycles using a small amount of starter and a lot of flour and water, the problem persisted. Perhaps if I had given it more time or tried even higher ratios of flour to starter, the smell would have gone away, but I ended up throwing the starter out as I didn't really need or want it as I had only made it as an experiment.

JMonkey's picture

I've not encountered this problem myself, but I did remember reading about it at Mike Avery's site, Sourdough Home. He quotes Debra, to whom I'd defer, myself, but I thought what he had to say was interesting.


There is one condition that seems to be irreversible. Sometimes you mix up a dough with your starter and the dough quickly gets very soft, it turns into a liquid. And the starter has a strong smell of acetone, or cheap fingernail polish remover. If this has happened, bacteria that can eat the protein in your starter have taken it over. Normally starch-eating bacteria are in your starter. If you don't feed it often enough, the protein-eating bacteria can take over.

Do you remember back in the Starting A Starter page when I talked about how a starter was like a weed patch that you were cultivating? At this point, one of the weeds has again taken over. And it is a very hard weed to eradicate. I know of two people who were able to beat back the protein-eating bacteria and have their old starter back. However, the other guy and I both found that the next time we skipped a starter feeding the bad bacteria took over again. The starter was undependable and unstable. Pouring it down the drain and starting over was the only real answer for me.

It is worth mentioning that the above paragraph has prompted more than a few conflicting comments from experts. Didier Rosada says that you are better off just pitching it and starting over. Debra Wink a well known hobbyist baker and biologist says she's recovered starters like this in 7 to 10 days. My view - in 7 to 10 days I can start a new known good starter, so I'd rather just start over.
breadnovice's picture


If it were illegal I would have to plead guilty of sourdough abuse. We don't make bread very often but have been making waffles, pancakes, biscuits, crepes and cakes for decades. I got my starter from my mother, she got it from her mother who got it as a wedding gift in 1917. We suspect it is of the San Francisco strain because of the taste.  After reading many pages of the forums I am impressed with the large amount of good information available, especially concerning the care of sourdough.  We have been doing so many things wrong.  Our system is to keep it in a glass gallon jar with a paper towel rubber banded to the top in the refrigerator. We would use it until there's a cup or two left, then dump in some flour and mix in some water until it's viscosity is some ware between cake batter and heavy cream.  Then it's into the back of the refrigerator for a couple of weeks while it works.  The reason we don't leave it on the counter top is at room temperature a few hours after feeding, it will volcano and spill all over.  It's a big mess and waste. We know it's ready when there is a thin layer of liquor on the top. There have been times we ignored it and had to lift off a thick layer of hard  gray blackish rubbery top, but it was fine. One time We had a three inch solid cracked crust on top and only had about a quarter of a cup left scraped from the crust. We fed it and it was fine.  Over all these years every time it was used I would taste it. Nobody else in the family would. It always tasted the same.  A while back I started measuring the flour and water by weight after reading it in the forums here.  I used it three weeks ago, it tasted the same. (it's definitely an acquired taste,) There was no liquor on top three days ago when I took it out to use it. The taste was a little off. The waffles were great and nobody got sick. It was time to clean the gallon jar so I put it in a two quart jar and fed it. 350g water and 350g flour. (another trick I learned in the forums here. Do the measurements in grams for the easy math.) I was concerned about the slightly off taste so yesterday I smelled it. For the first time in all these years, I smelled the acetone. Of course this is the first place I came to for help.  I'm now worried now for two reasons. One it seems to be a common occurrence and two, I never smelled it while it was working. I always smelled and tasted it after it was worked out and dormant. Btw it tastes fine.  I guess the amoral of this story is, take good care of your sourdough but if you don't it'll probably be ok. A friend told me, You can keep an insurance start by drying it on some aluminum foil in a bowl covered by a cloth or paper towel. When dry fold it up and put it in the freezer.

Reni's picture

I have a starter that I started out with flour, yogurt and water. It was supposed to be fed every 24 hrs and then switched to every 12 hrs and this was to go on for 14 days. The last week it started to smell like acetone, I fed it more flour grams and more water grams, that didn't eliminate the acetone smell. Soooo, I started feeding it three times a day. The smell has subsided a bit and is smelling more like sweet sour. The thing is, it rises up quite fast. Hopefully this will work because tomorrow is the last day - fingers crossed.

Reni's picture

I also always taste a bit of it before I feed it, it has always had that sour tang to it. Hope this helps someone to know that you have to play around with things. I bet I could lower the grams and it would not rise up so fast? Also, after the first week I stopped weighing I just get the consistency I like.

doughooker's picture

You need to lower the pH in the starter to combat the particular bacteria making the acetone aroma.

Which particular bacteria produce acetone? What is the name of them?