Acetone?

Is this a new starter that you are growing? If so, it is common to get that acetone smell in the early stages. Just dump most of it out, saving only a couple of spoonfuls and feed it again. Stir vigorously several times a day. It will come out of it and be fine. It might take a few feedings but you will notice it improving steadily.

Oh, and yes--starters do produce acetic acid but not in excess when they are healthy. A healthy starter will smell good. 

Two days ago I threw out a starter that smelled like that. It almost knocked me over when I took the lid off. It was my original starter made 5 or 6 months ago. I fed it all the time and it always doubled fast and furious. Luckily I took some of it and started a new batch just for the heck of it a couple of months ago before the vinegar came and this new starter is really fast to double/triple and smells so nice. No matter what I did to the vinegar one it wouldn't  get nice. I even threw out all but a teaspoon and fed again. It grew and grew but the smell was not something I felt comfortable with so I tossed it. I took off some of my sweet smelling starter to start another batch just in case this one goes to vinegar. Maybe it was ok to use but I tossed it. Good luck with yours.                    weavershouse

Thanks for all the postings here on this topic.

Weavershouse, your experience is identical to the experiences I've had.  It's somewhat comforting to know the same things are occuring for others - globally!  Although it is never pleasant to have to make that decision to bin your precious starter.

I've had some difficulty knowing what to do with a starter that has begun producing an acetone-like aroma, so my response was the same as yours. Like you I couldn't change the aroma via feeding & hydration methods, so it finally ended up being composted.

Thanks for sharing and thereby showing that no matter where we are in the kitchen or in the world, we are all facing the same -if not identical issues with our craft.

Cheers

Marie