Banana flavor from stressed yeast?

[homemaltster]

Got a bit of a head-scratcher. I just kegged a blonde ale that has turned out to have quite the banana flavor. The confusing part is that I did not do any of the typical things to get esters: my fermentation temp was lower than normal, I aerated plenty (15 minutes for two gallons of wort), and made a good-sized starter.

The yeast health is the most suspect. I used yeast saved from my last batch, which was a 100% oat beer that had some fruitiness. I had pitched a smack pack of Wyeast 1272 American Ale II into the oat beer, then harvested the yeast slurry post-fermentation. It sat in my fridge for four weeks, which I realize is a bit long. Then I made a starter 20 hours in advance, but my DIY stir plate wasn't working, so I just shook it every so often and it was fairly active. Once I pitched it, fermentation seemed to go fine.

Does the banana flavor confirm that my yeast were underpitched or stressed?

 

[seabrew8]

Got a bit of a head-scratcher. I just kegged a blonde ale that has turned out to have quite the banana flavor. The confusing part is that I did not do any of the typical things to get esters: my fermentation temp was lower than normal, I aerated plenty (15 minutes for two gallons of wort), and made a good-sized starter.

The yeast health is the most suspect. I used yeast saved from my last batch, which was a 100% oat beer that had some fruitiness. I had pitched a smack pack of Wyeast 1272 American Ale II into the oat beer, then harvested the yeast slurry post-fermentation. It sat in my fridge for four weeks, which I realize is a bit long. Then I made a starter 20 hours in advance, but my DIY stir plate wasn't working, so I just shook it every so often and it was fairly active. Once I pitched it, fermentation seemed to go fine.

Does the banana flavor confirm that my yeast were underpitched or stressed?

Hats off for the detailed log man. Doesn't confirm very much.

 

[sky4meplease]

How much yeast did you pitch?
For two gallons you probably only needed 40 billion cells. That's like 20-30 milliliters or two tablespoons of slurry.

 

[BigMack]

I use 1272 all the time. I've used it for 10 harvested generations as well as used slurry from the fridge that was 2 months old with no starter. I've never had anything even close to banana flavors from it. It can get a tiny bit fruity if fermented warm, but it is a light citrus flavor that I can't imagine would be mistaken for banana. I'm not saying it couldn't have been the yeast, but it sounds like you pitched more than enough cells into well aerated wort for a healthy fermentation.

 

[garcia]

Maybe try a diacetyl rest. Up temp 10f and wait a week. Works wonders with lagers.

 

[madscientist451]

Got a bit of a head-scratcher. I just kegged a blonde ale that has turned out to have quite the banana flavor.

Does the banana flavor confirm that my yeast were underpitched or stressed?

Was the banana flavor there before you kegged it?

 

[homemaltster]

How much yeast did you pitch?
For two gallons you probably only needed 40 billion cells. That's like 20-30 milliliters or two tablespoons of slurry.

We pitched at least half a cup of slurry, so yeah, that should have been more than enough.

Was the banana flavor there before you kegged it?

The was indeed there before kegging.

Maybe try a diacetyl rest. Up temp 10f and wait a week. Works wonders with lagers.

Didn't have the buttery diacetyl taste at all. Can a diacetyl rest deal with esters too? Doesn't seem like it would...

 

[billl]

There is nothing special about the "diacetyl" part of the diacetyl rest. It's just warming the yeast up enough that they quickly finish the last bits of fermentation cleanup.

Unfortunately, Banana esters aren't really something normal sach yeast clean up. Fortunately, it's a highly volatile ester that tends to fade quickly. It's one of the reasons people advise drinking Hefe's as fresh as possible.

If it's a complete banana bomb to the point where you don't want to drink it, you could pitch some brett and let them go to work on those esters.

 

[homemaltster]

Fortunately, it's a highly volatile ester that tends to fade quickly. It's one of the reasons people advise drinking Hefe's as fresh as possible.

I kegged it four days ago and the banana flavor was strong. Then tasted it two days ago and banana was still quite present. Tried it again today, and the banana is almost nonexistent.

I guess that counts as a victory against off-flavors, though I was starting to like what the banana added. Oh well...