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So last week I made a 9L batch of chocolate porter. Normally I let it ferment in a small carboy and just put a tin foil cap on it for the first day or two then put the airlock. Well, it turns out that I forgot to put the airlock until about 5 days since fermentation began. I tried it and it tasted fine and then I got the crazy idea of leaving it off to see what would happen (thats the beauty of making small batches). I tried it today and I would say it is the perfect definition of oxidation. All kinds of papery, sherry-like, cardboard etc... definitely not in anyway whatsoever tasty. But I'm glad I got to try it because I've never tasted a beer this oxidized. This is definitely an interesting beer for anyone who wants to experience oxidation in its fullest form. Anyway, anybody want to try an oxidized beer? If there is interest I'll bottle a few, if not it's going down the drain.

Sounds like a great learning experience.

Are you able to make it to the BJCP get together at Jeff's on Friday? If so, maybe bring a bottle or two there, I'd like to try it.
Thanks!

Adam, I left some beer in a pitcher in the fridge for 10 days, and had a few tastes, more than one, so I would know. All I could pick up really was vinegary sourness with that. I will probably do it again some time. I picked up cardboard in a beer at a pub before. Don't have any training like you though. I'd like to try a bottle next time you are coming through Wolfville please. I think I am learning Diacetyl in commercial beer a bit better now.

Ok, I'll bottle some up!

Does the Sherry like flavour add sweetness? One of the small kegs at my father-in-laws "went sweet", but he still kept drinking it. He does all sorts with those kegs, and even took a lid off one once. I think I mentioned about the filthy CO2 hook up. He might have left the pressure relief valve open, possibly?

Yeah I guess you could describe it as sweet, in my beer I would call it more fruity though. I can't see any other reason for a beer going "sweet".

Chalmers, yes I'll be at the BCJP thing on Friday.

Thanks, I think that's right then. Come to think of it, it was a bit like sherry also. He must have left the pressure relief valve up (he likes low carbonation), or opened the darn lid again to pour some out when he couldn't get the CO2 working, or maybe perhaps more likely let the pressure run very low and the seals failed, he only hooks the CO2 up when he really has to.

I might have already tasted your beer, in that case.

CartoonCod wrote:So last week I made a 9L batch of chocolate porter. Normally I let it ferment in a small carboy and just put a tin foil cap on it for the first day or two then put the airlock. Well, it turns out that I forgot to put the airlock until about 5 days since fermentation began. I tried it and it tasted fine and then I got the crazy idea of leaving it off to see what would happen (thats the beauty of making small batches). I tried it today and I would say it is the perfect definition of oxidation. All kinds of papery, sherry-like, cardboard etc... definitely not in anyway whatsoever tasty. But I'm glad I got to try it because I've never tasted a beer this oxidized. This is definitely an interesting beer for anyone who wants to experience oxidation in its fullest form. Anyway, anybody want to try an oxidized beer? If there is interest I'll bottle a few, if not it's going down the drain.

Do you suppose air made it down through the blanket of CO2? I'm pretty sure open fermentation for 5 days won't oxidize beer. Just sayin'

Transmitted from the hop-phone.

I agree 100%. I wasn't clear with my dates. 5 days after fermentation began I took a gravity sample, the beer was at 1.014 (expected final gravity) and it tasted fine, chocolaty, roasty as expected. Then 4 days later (so 9 days in total with just the tin foil cap) I tried it again. The gravity remained the same and thats when I noticed it was oxidized.

I was doing some thinking and some reading about gas mixing and oxidation and here is what I've come up with to explain what happened. Initially I figured the CO2 blanket would protect the beer from oxygen (since CO2 is heavier than O2), and while the beer is actively producing CO2 I figure it does this. However after CO2 production stops oxygen will slowly diffuse into the CO2 blanket. This fits my scenario because the beer was essentially finished after the first 5 days, and it got oxidized after 4 days of no active fermentation.

Here is a quote from Principles of Brewing Science (p167, second edition):
"Initially, the gases in the headspace will stratify according to weight; i.e., the 0.5 mL volume of air will sit above a CO2 layer. Henry's law, however, asserts that, at equilibrium, the gases will act as if each were the only gas present."

I bottled a six pack today. I'll bring some to the BJCP meeting for anybody that wants to try. Mark, I'll also bring one down next time I head to Clare.

Great! thanks Adam. Be nice to see you guys again.