Yeast starter smells like vinegar???

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Well-Known Member
Jan 17, 2009
Reaction score
Dover, PA
So I made a yeast starter on Thursday night which consisted of White Labs WLP001 California Ale Yeast, 1/2 cup of DME, and 2 cups of water in a flask. I fermented it at about 72* in a dark cabinet. I had a HIGH krausen, as it reached the tin foil that was tightly wrapped around the top. I thought everything was good, as there was a nice white buildup on the bottom with a couple clumps of white yeast floating around. Well, I did my first all grain today :rockin:which was AWESOME:rockin:!!! It's a Yeungling Lager clone, except I'm not using Lager yeast, just an ale yeast. What the heck, why not... I used this recipe:

When I took the foil off the starter flask/beaker, I noticed it smelled like vinegar. The first thing I thought of was infection. I didn't pitch it. Is it possible that this smell is because I fermented the starter too high, but 72* seems reasonable. I didn't want to ruin 3 hours of work (and the $$) using yeast that I question. I threw the beaker into the fridge to take to my LHBS tomorrow at lunch time to see what they think about it. I'll probably just get a pack of dry yeast and pitch that at lunch tomorrow.

I sealed the fermenter with everything including an airlock, hopefully she'll be fine for yeast tomorrow after re-aerating. What do you guys think about the vinegar smell? What's a good, quick starting dry yeast that can ferment 1.057 ale pretty cleanly?

safale us 05 is damn similar to wlp001 and its dry. As for the starter- it deffinitly should not be vinegary although not sure what it is.
TASTE IT before you do anything drastic. Fermentation gives off all kinds of crazy smells, especially in a starter.

My last two starters have had a sour vinegar aroma that sounds similar to what you're talking about. The first was WLP007 Dry English Ale, and the second was Bell's yeast cultured from the bottle. Both were on a stir plate, and both were 2L starters. A couple friends had starters of the same strain going at the same time (we were doing a side by side brew of the same recipe, Founders Breakfast Stout) and they commented that theirs smelled the same way. Because of that, we all went ahead and used the yeast and the beers turned out FANTASTIC. Not a hint of infection.

We both noticed similar smells from our separate cultured Bell's yeast starters. Those got pitched (into the beer, not the trash) on Saturday and so far so good. After I crashed my starter, I collected some of the decanted "beer" and tasted it, and it tasted just fine, again no hints of sourness.

Our only conclusion was that we were smelling acetaldehyde or some other fermentation byproduct.

Ultimately, I would taste it and if all seems good, go with it. If there's any doubt, go the US-05 route, it's the same yeast and the dry package contains a pitchable quantity.
My WLP001 starters always smell bad, but the beer always turns out good.
All my starters AND fermentations smell awful.
I was gonna say something similar. Not all smell bad and the fermentations often don't smell that bad but most of my starters and Fast Ferment Tests smell/taste bad.

I brewed an IPA Saturday and severly over-pitched the FFT. I put the FFT on the stirplate Saturday afternoon and it was going strong that night. I tested it this morning so it had about 36 hours total. It had a distinct vinegar-y odor but I'd be surprised if there was enough time for the yeast to create the alcohol, then for the acetobacter to create the vinegar from the alcohol. I've had other FFTs smell awful but the beer was great.
I brewed an AHS Texas Blonde minimash kit about two and a half weeks ago. I thought it was ruined because it had a mild smell of vinegar while fermenting. It wasn't overpowering, but it was obviously there. I've had gross sulphur / fart smells and don't worry about that, but this clearly smelled like vinegar. Anyway, I decided to let it run it's course and last night sampled some from the fermenter. No vinegar taste at all. So it's cold crashing in the keezer and I'm going to keg it tomorrow. I expect it to be fine when it's carbed up.
Especially if you're using a stirplate, things can smell bad. You're adding a lot of oxygen to the starter, so getting oxidized aromas and flavors is common. My starters often smell and taste cidery and stale. I can't say I've had a lot of vinegary aromas though. Did you taste it? If it tastes vinegary, I wouldn't use it.
Real vinegar = Acetobacter; not the best ju-ju.

The good thing is this bug does need oxygen to make vinegar, which is why some folks' starters have vinegar but their fermentation doesn't.

Taste it as suggested, proceed with caution, YMMV, etc.