Yeast start has beer/vinegar smell

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Soeze

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I started a yeast starter a couple days ago and chilled it for 24 hours. I am about step it up again tonight however when I took off the foam stopper it had a beer/vinegar smell to it. Does that mean my yeast are contaminated? And if not would it be okay come brew day?

Thanks for the help!
Soeze
 
Starters smell weird sometimes, its beer thats fermented for 2 days at usually too high a temp. take a taste of the starter beer, if there is a clear vinegar taste id be cautious and use dry yeast.
 
My starter smells funny also, but it doesn't taste bad but yeasty. I think that this funny smell is just beer with no hops.
 
For my last batch the starter ended up smelling like cider or vinegar, but the beer itself came out fine. I wonder if it has something to do with no hops being used in the starter mix...
 
I imagine the vinegar (acetic acid) you are getting is coming from oxidation in these cases. Ethanol oxidizes into acetaldehyde, and acetaldehyde in turn can oxidize into acetic acid. However, this usually only results in softer, sherry-like character as opposed to full on vinegar. A stronger vinegar character often indicates acetobacter contamination. Given below is an old article from George Fix that talks a lot about oxidation.

http://www.morebeer.com/articles/oxidation_in_beer
 

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