My last batch had a thin whitish 'membrane' on top of it and some white spots, visible on the picture bellow.

I think I saw something similar on a blog a while ago, attributed to a lactobacilus infection.

Taste was not too bad, but the smell was a bit strange, I went ahead and bottled 3 days ago.

What is that? Should I be prepared for bottle bombs?


1 Answer 1


A bit tricky to tell, but it could be early stages of a lactobacillus or pediococcus contamination. The flaky white patches are typical of lactobacillus, while short segments of ropes you see are typical of pediococcus, although I would swing towards lactobacillus on this one.

Lactobacillus contamination:

Lactobacillus contamination

Pediococcus contamination:

Pediococcus contamination

Either way, it's clearly a contamination of some kind, so best to be safe with the bottling and bottle with plastic soda bottles. Stored cold, any decrease in SG will take several months, and not all strains produce CO2 - but I never take chances with glass.

  • Too late, got them on glass already. will follow closely and store cold as soon as it is carbonated. Is pediococcus contaminated beer safe To drink? That looks nasty. Commented Mar 17, 2013 at 8:39
  • hehe, yes, it's safe to drink - it it weren't, lambics wouldn't be half as popular as they are! On first sight it looks nasty, but then so does a krausen to some. It's a collection of dextrins, proteins and some slime to help keep oxygen out of the beer. No pathogens harmful to humans can grow in beer.
    – mdma
    Commented Mar 17, 2013 at 10:34
  • That being said, not everyone likes sour beer. Me for instance. Can't stand the stuff. Commented Mar 17, 2013 at 15:27
  • 1
    He asked if it was safe to drink - not to be blunt, but I don't see what your personal preference has to do with that. Sure, some people like it, others don't, but that's how it is with all types of beer.
    – mdma
    Commented Mar 17, 2013 at 15:59
  • I had a pediococcus-style spiderweb appear on a black English Pale Ale once, right at the end of dry hopping. I kegged it anyway and it was delicious, with no noticeable sour flavor. Don't worry about an infection until the beer tastes like: bandaids; burnt rubber; wet goat; pineapple; or cherry pie. And even then, if its any of those last 3, just let it ride a year and call it a Flemish Sour.
    – GHP
    Commented Mar 18, 2013 at 12:11

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