Contamination

the butcher · 02-27-2007, 11:32 PM

Hey all! I've been brewing for 10 or so years on and off and had only one problem with contaminated beer......well up until this last batch. Its a pale ale, and I used sierra nevada yeast, (I do propogate my yeast and have been for quite some time) ........anyway, I noticed a slightly off smell when the beer was in the fermenter, I generally brew lagers and thought it was probably just the ale yeast. Well, here we are 3 weeks after bottling and the beer has a kind of butterscotch (Its hard to describe) aftertaste. The beer is not overcarbonated and doesnt foam excessively, it cleared nicely too......So the question is, what happened, and is it safe to drink?? Its not terribly bad (and I HATE to dump 4 cases) But I dont want to get sick either......I am a stickler for sanitation and I'm thinking my yeast maybe was contaminated....any ideas/suggestions????
I'm guessing it'll have to be dumped.

Thanks in advance, and happy brewin!

**Brewtopia** · 02-27-2007, 11:44 PM

Butterscotch off flavors are usually associated with Diacetyl. Could be caused by a bacterial infection in the yeast sediment. It is an acceptable flavor in some styles. Whatever it is, it is not going to hurt you or make you sick. There is no harmful bacteria that can survive in fermented beer. If it's drinkable, drink it.

carpe3dm · 03-01-2007, 08:23 PM

Diacetyl is detectable in beer at concentrations as low as fifty parts per billion. At low levels, it gives beer a slick mouthfeel; at higher levels, the flavor becomes buttery, then like butterscotch, and eventually rancid. One possible source of diacetyl is bacterial infection. Pediococcus and Lactobacillus are notorious producers of diacetyl. If you can detect other off flavours like sourness, “rope”, or other odd aromas, infection is probably your problem.
As brewtopia said, no harmful bacteria can survive so if it doesn't taste half bad, drink it up! It might be interesting to do an experiment and save a few bottles for a couple of months. If the bacteria are responsible for the diacetyl, they will probably produce more of it, and you may be able to detect a flavor difference. If you do notice a difference, then at least you will know what happened.

zoebisch01 · 03-01-2007, 08:35 PM

I have an amber APA I brew that uses Coopers dry ale yeast which seems to produce copious amounts of diacetyl. I have noticed in conditioning that once it hits the 4th week mark it is like the diacetyl dramatically disappears leaving only a small hint of it. I continue using the Coopers. Why? Because the small amount of residual diacetyl lends an interesting dimension to the beer. Give it a few more weeks. Warmer temperatures I believe help the yeast to get active and reabsorb diacetyl (somebody correct me if I am wrong), in other words your conditioning temps may delay this if too cold...although I am not sure what 'too cold' would be.

the butcher · 03-02-2007, 10:57 PM

hey thanks guys. On your advice, I drank a few last night with no ill affects! It seems if the beer is colder, the taste is much less noticable........I cooked up another batch today with fresh yeast, everything is right with the world!!......