I've got a bit of mold on top of my wort. My situation is a bit different than what others seem to have encountered... I made the wort about 5 days ago and hadn't gotten around to pitching the yeast.

So my question is, if no known pathogens can survive in beer, does that apply in this case if the fermentation finishes?

  • 2
    I won't add another answer, but definitely toss it. You can't let the wort sit more than a few hours without pitching if its exposed to the air. However, look up "No Chill Brewing" if you want to be able to pitch the day after (or later) your brew day. Its a way of doing it safely.
    – GHP
    Commented Oct 3, 2011 at 12:11
  • I wouldn't leave wort exposed to air for even an hour, let alone a few. I know no chill brewing is popular right now, but I don't think it's a best practice, even if the wort is sealed up. Yeast production tend to overwhelm the few stray critters you normally get.
    – TinCoyote
    Commented Oct 3, 2011 at 22:48
  • I have often left my wort in the carboy with an airlock overnight prior to pitching, but never 5 days. I think its toast.
    – brewchez
    Commented Oct 3, 2011 at 23:05

2 Answers 2


I don't think you have to worry about being harmed by the beer, but you probably should worry about the flavor. If there's mold on top, I'd toss it.

  • I agree, toss it. Sorry man. Upvoted.
    – TinCoyote
    Commented Oct 3, 2011 at 22:47
  • I seriously considered giving it a taste, but you all have talked me out of it!
    – bdaniels
    Commented Oct 13, 2011 at 19:45

Sometimes the problem is not with the microorganisms themselves, which will be destroyed by heating, but with the toxins they produce, which won't be; salmonella works this way, for instance. We try to pitch large, healthy populations of yeast so they out compete undesirable microorganisms for the sugars. If it's already moldy, I think you've lost that race. And while "spontaneous fermentation" has been used for thousands of years, mold has never been desirable. :) As well, fermentation isn't going to clean up anything nasty that's already there. I say "toss it".

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