Raspberry Stout contamination?

I brewed a 5-gallon batch of Frankenberry Chocolate Raspberry Stout July 20 (11 days ago) using a Scottish Ale Wyeast. The yeast was pitched at 78 degrees, everything was sanitary, I immediately placed the airlock on the plastic fermenter where it is now.

EXCEPT my husband didn't seal the lid on the primary, just had it sitting on there, closed, but not sealed. No activity in the airlock, small, white filmy bubbles.

Should I take a gravity reading? It smells very yeasty. I'm hoping it is just suspended yeast?

My last batch of this turned out great, no problem with fermentation.!I'm supposed to add raspberry puree at the 14 day mark. Didn't want the added expense if it's contaminated, though. Here is a picture:

Topic contamination homebrew

Category Mac

1
answered at

It looks OK - it's quite common for bits of yeast to still be floating on the top of the beer. If you search google images for "beer pellicle", you'll see what a contamination can typically look like - it depends of course, but commonly they are a grey-white web-like filmy layer. Light-Brown foamy bubbles are krausen (yeast + brew residue foam), which typically rise up initially, then sink back down as fermentation progresses.

Leaving the lid unsealed only adds an extra risk-factor to getting infected, it's not a sure thing.

I would take a sample just before committing on the raspberry. After 11 days fermenting, the base beer should be quite close to finishing. If the beer tastes OK, it probably is OK. Obviously also check the gravity at this time.

1
answered at

"White filmy bubbles" don't on their own sound like biological contamination , especially after 11 days.

I would not worry too much about the lid of the bucket not being completely sealed. So long as it was basically closed, that should prevent any active organisms (flies, bugs, &c.) from getting in. Airborne bacteria and other spoiling agents can't really travel "up" and around obstructions (eg. Pasteur's swan-neck flask experiment). The lack of a solid "seal" would also explain the lack of airlock activity, as the CO₂ had alternate means of escape.

Does it smell bad? Does a (sanitary-ily retrieved) sample taste okay? Then it's probably good to go.

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