I brewed a double batch of IPA with a buddy about 8 weeks ago.

We split this into two 5 gallon pails and 2 weeks later into two carboys. His was fine, but mine developed a bit of white stuff on the top of the beer.

It smelt fine and tasted OK so I bottled it after 2 more weeks.

After being in the bottles about 10 days I decided to try some. I noticed that all the bottles had a slight white film on the top of the beer.

I poured a bit and there was a slight taste that was off to it. A bit sour maybe or alcohol-y. Not too bad but a hint.

I decided to leave it and two weeks later (last night) tried another bottle. It tastes fine now, but the white film is still there - although not getting worse.

When I poor the beer this film separates into little flecks of white that will float on the surface in my glass. Not a lot, but I notice it.

I'm thinking the carboy I used wasn't as sanitized as it should have been.

I'm curious as to what this may be and if it is safe to drink it. I don't want to give something to my friends when they are over that may make them sick in any way.

  • 2
    Do you taste more diacetyl (buttery) in your beer than you can in your buddy's?
    – baka
    Commented Mar 22, 2011 at 12:38
  • My understanding is that diacetyl doesn't show up visibly, am I wrong about that, or are you getting at something else? Just curious.
    – TinCoyote
    Commented Mar 22, 2011 at 15:19
  • 2
    Pediococcus will throw diacetyl in noticable amounts when it isn't used in combination with something that will consume the diacetyl (like Brettanomyces).
    – baka
    Commented Mar 22, 2011 at 15:22
  • I guess you could say it is a bit buttery, not the first word that came to mind. I tasted it a bit in my buddies but it was also a few weeks ago and quite young. Is Pediococcus something to worry about?
    – applecran
    Commented Mar 23, 2011 at 3:56

1 Answer 1


The general rule is as long as a beer doesn't smell or taste off, it's probably okay to drink.

It sounds to me like you have a Lactobacillus contamination. Lacto will give the beer a sour taste and that taste will increase over time. That's the white film and flecks.

It matches every description I've heard of for a lacto contamination.

Hopefully others will have more direct experience to tell you about your specific contamination. But if it is lacto, you are gonna want to drink it before it becomes too sour to drink.

Lacto is used along with Brettanomyces bruxellensis or other brett strains to make lambics. Neither will hurt you, but in a non-lambic beer it is a flaw.

Good luck with it, I hope this helps!

  • 4
    I think there's too much hops in an IPA for Lacto to get a foothold. Pediococcus will produce lactic acid, though, so that may be the bug.
    – baka
    Commented Mar 22, 2011 at 12:35
  • Excellent point, baka. Pediococcus is a possibility as well.
    – TinCoyote
    Commented Mar 22, 2011 at 15:18

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