Banana smell from fermenting Brown Ale?

So, I did my first PM on Sunday - Newcastle Clone with 3.5lbs of grain. By yesterday morning it was bubbling away in the primary and smelt just as I would expect it to. I get home from work this evening, stick my nose near the airlock, and give the top of the bucket a little push... holy banana!

The ambient temp in the room is around 70 and doesn't fluctuate much at all. Also, this is the same place, temp, and fermenter I've fermented all of my other brews (including a Newcastle Extract Clone) and never had this before. I've always associated that smell with a nice wheat beer and higher fermentation temps. Is there another reason for this?

That sounds like high fermentation temps to me. Ambient temperature isn't all that good a guide to the temps in your beer - fermentation is exothermic and can be eight to ten points higher than ambient temperature, so it's possible your yeasties are sitting at around 80F, which depending on the yeast could well be a banana-inducing temperature. I'd try to get it cooler if you can, at least for two or three days until fermentation activity subsides.

Danek said:

That sounds like high fermentation temps to me. Ambient temperature isn't all that good a guide to the temps in your beer - fermentation is exothermic and can be eight to ten points higher than ambient temperature, so it's possible your yeasties are sitting at around 80F, which depending on the yeast could well be a banana-inducing temperature. I'd try to get it cooler if you can, at least for two or three days until fermentation activity subsides.

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That's what I figured. I'm considering just leaving it and seeing what happens though. It was a pretty vigorous fermentation for the past 2 days. How much can I impact the end result by cooling it down now? Or is the "damage" done already? I might just LDWHAHB and see how it turns out. Although, it's hard to imagine a brown ale that "dirty"!

My first beer was an IPA fermented way too high. We had an unexpected hot spell when ambient temp was in the 80s, and the beer was undrinkable due to excessive banananess. To be fair, I'd screwed the beer up in a variety of ways and ferm temps was but one problem of many. For your brew, if the beer is still fermenting, I'd say it's still worth trying to rein it in if you can. If not, then it could still be perfectly fine - as you say, a brown ale is a pretty forgiving style, so I wouldn't worry too hard.

Danek said:

My first beer was an IPA fermented way too high. We had an unexpected hot spell when ambient temp was in the 80s, and the beer was undrinkable due to excessive banananess. To be fair, I'd screwed the beer up in a variety of ways and ferm temps was but one problem of many. For your brew, if the beer is still fermenting, I'd say it's still worth trying to rein it in if you can. If not, then it could still be perfectly fine - as you say, a brown ale is a pretty forgiving style, so I wouldn't worry too hard.

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I think I'll try to cool it down for the rest of the time it's in the primary. If the banana smell prevails, I'll just pretend it was on purpose and call it something like "Brown Banana Ale". I suppose it would be up to people's interpretation as to how someones "banana" might get "brown". :rockin:

I think it is harmless and will go away as fermentation progresses. Most of mine do that, but the finished beer hasn't smelled fruity yet.

Maybe it's a trait of Nottingham yeast?

Isoamyl acetate.

It'll probably turn out fine but as always if fermentation got too warm I would leave it in the primary one more week than you originally planned for the yeasties to clean up.

Saccharomyces said:

Isoamyl acetate.

It'll probably turn out fine but as always if fermentation got too warm I would leave it in the primary one more week than you originally planned for the yeasties to clean up.

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Good call.

Craig311 said:

I think I'll try to cool it down for the rest of the time it's in the primary. If the banana smell prevails, I'll just pretend it was on purpose and call it something like "Brown Banana Ale". I suppose it would be up to people's interpretation as to how someones "banana" might get "brown". :rockin:

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Banna Nut Ale, kinda like Banna Nut Bread...

Zadeun said:

Banna Nut Ale, kinda like Banna Nut Bread...

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I tried this once:

Wells Banana Bread Beer from Wells & Youngs, a English Strong Ale style beer

I thought it sucked ass a little bit.

Could be a nice little banana brown. Remember that SOME people like a little banana in their beer.

Keep in mind that a vigorous fermentation can add 5-7+ degrees to the wort temp, an ambient of 70 could mean upper 70's wort temp.

As for the banana ester, it will dissipate over time in my experience. I made a hefe that fermented high and the initial beers were strong, though over a few months it all but went away.