Banana ester in my lager after diacetyl rest

[wmsouthworth]

Hello,

I just got back into brewing after a ten year break. I have brewed some tasty ales in the last couple of months, so I tried my hand at a lager. I just finished the Diacetyl rest and suddenly my box freezer smells like bananas. Will this go away during lagering? I used WLP830 German lager yeast, a 2 liter starter in 5 gallons. Oxygenated with a difussion stone. Fermented at 52-54 degrees F. Then a diacetyl rest for 3 days at 55-57 degrees. Any hope for this beer?

[blatz]

sounds like underpitching.

your starter, is small by a factor of about 3-4 if you assume extremely fresh yeast.

larger starter, stir plated starter or use S. Cerevisae's recommended method of a 'shaken not stirred starter'.

I am pretty certain that ester won't ever fully exit the beer, although it may weaken over time to the point of being at least enjoyable.

btw - its still young, and it may just be the off smells of fermentation. 

[wmsouthworth]

sounds like underpitching.

your starter, is small by a factor of about 3-4 if you assume extremely fresh yeast.

larger starter, stir plated starter or use S. Cerevisae's recommended method of a 'shaken not stirred starter'.

I am pretty certain that ester won't ever fully exit the beer, although it may weaken over time to the point of being at least enjoyable.

btw - its still young, and it may just be the off smells of fermentation.

Thanks for the info. Next time I will use a much larger starter. I'm going to lager it and see what happens, but I don't have much of hope.

[S. cerevisiae]

A 2L starter in five gallons is not underpitching by any stretch of the imagination.  That's a roughly a 10-to-1 step.  My bet is on wort composition.  Banana is the ester known as isoamyl acetate, which is formed via a condensation reaction between isoamyl alcohol (a.k.a. isopentanol) and acetic acid.

C₅H₁₂OH + CH₃COOH  → C₇H₁₄O₂ + H₂O

The reaction shown above reads isoamyl alcohol plus acetic acid produces isoamyl acetate plus water.   What this reaction means in layman's terms is that your fermentation generated isoamyl alcohol, and there was acetic acid available with which to form isoamyl acetate.  Acidic acid comes from acetyl-CoA.  We know that higher alcohol (isoamyl alcohol is a higher alcohol) production increases with biomass growth; however, so does acetyl-CoA utilization.  On the other hand, overpitching results in elevated acetyl-CoA and lower higher alcohol production.  This batch was neither overpitched nor underpitched, which means that something else went wrong.   What was the original gravity?  What was the wort composition?  How much trub did you carry over from the kettle?
 

[wmsouthworth]

A 2L starter in five gallons is not underpitching by any stretch of the imagination.  That's a roughly a 10-to-1 step.  My bet is on wort composition.  Banana is the ester known as isoamyl acetate, which is formed via a condensation reaction between isoamyl alcohol (a.k.a. isopentanol) and acetic acid.

C₅H₁₂OH + CH₃COOH  → C₇H₁₄O₂ + H₂O

The reaction shown above reads isoamyl alcohol plus acetic acid produces isoamyl acetate plus water.   What this reaction means in layman's terms is that your fermentation generated isoamyl alcohol, and there was acetic acid available with which to form isoamyl alcohol.  Acidic acid comes from acetyl-CoA.  We know that higher alcohol (isoamyl alcohol is a higher alcohol) production increases with biomass growth; however, so does acetyl-CoA utilization.  On the other hand, overpitching results in elevated acetyl-CoA lower and lower higher alcohol production.  This batch was neither overpitched nor underpitched, which means that something else went wrong.   What was the original gravity?  What was the wort composition?  How much trub did you carry over from the kettle?
 

The original gravity was 1.051, it was a extract brew, 100% pilsner liquid malt extract from morebeer. I racked off the trub after letting it settle for 3 hours. I did pitch at 60 degrees which I now know is not good. The other thing I now know I did wrong is I added all of wort from the starter rather than pouring of most off the liquid.

[duboman]

I would pull it from the chamber and let it rise and finish and then lager, IMO, at less than 60 for only 3 days wasn't enough d-rest, mine usually get into the low-mid 60s and finish nicely.



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[wmsouthworth]

I would pull it from the chamber and let it rise and finish and then lager, IMO, at less than 60 for only 3 days wasn't enough d-rest, mine usually get into the low-mid 60s and finish nicely.



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I'll give that a try. Thanks.

[brulosopher]

A 2L starter in five gallons is not underpitching by any stretch of the imagination.  That's a roughly a 10-to-1 step.  My bet is on wort composition.  Banana is the ester known as isoamyl acetate, which is formed via a condensation reaction between isoamyl alcohol (a.k.a. isopentanol) and acetic acid.

C₅H₁₂OH + CH₃COOH  → C₇H₁₄O₂ + H₂O

The reaction shown above reads isoamyl alcohol plus acetic acid produces isoamyl acetate plus water.   What this reaction means in layman's terms is that your fermentation generated isoamyl alcohol, and there was acetic acid available with which to form isoamyl alcohol.  Acidic acid comes from acetyl-CoA.  We know that higher alcohol (isoamyl alcohol is a higher alcohol) production increases with biomass growth; however, so does acetyl-CoA utilization.  On the other hand, overpitching results in elevated acetyl-CoA and lower higher alcohol production.  This batch was neither overpitched nor underpitched, which means that something else went wrong.   What was the original gravity?  What was the wort composition?  How much trub did you carry over from the kettle?

Yes! I was going to make some similar allusions without all the actual science to back it up.

This beer was not technically underpitched.

The original gravity was 1.051, it was a extract brew, 100% pilsner liquid malt extract from morebeer. I racked off the trub after letting it settle for 3 hours. I did pitch at 60 degrees which I now know is not good. The other thing I now know I did wrong is I added all of wort from the starter rather than pouring of most off the liquid.

I'm doubtful the starter beer had any lasting impact on the character of your beer. I have a more formal xBmt planned, but in my experience, even 2L of starter pitched without decanting imparts little if any noticeable character.

If I had to guess, the beer is either too young and you're perceiving something other than isoamyl acetate, or you picked up a wild yeast at some point.

[rabeb25]

Was this beer by chance brewed via decoction?

[blatz]

while I understand the science behind it, in practice, the only 2 times (of the more than 80 batches of lager i've made) that I've gotten the banana ester was early in my brewing when I pitched a single smackpack into a 5 gal batch and most recently, when I tried to use the shaken not stirred approach on a vienna.  after 5 weeks of lagering, i dumped the latter this weekend.

i've had a lot more success stepping up a stir plated starter and pitching in the ballpark of what the yeast calcs say.  may not be what is being touted these days, but it works well for me. 

Was this beer by chance brewed via decoction?

I think he said it was extract.

[S. cerevisiae]

If I had to guess, the beer is either too young and you're perceiving something other than isoamyl acetate, or you picked up a wild yeast at some point.

The problem could be due to a wild yeast or bacteria infection, but it could also be due to a mislabeled vial of yeast.  It does happen from time to time.  The only thing that could rule out receiving a mislabeled vial of yeast is fermentation temperature.  However, then again, fermentation temperature would also rule out wild microflora, which leads us back to wort composition, complete lack of trub, and/or dissolved O₂ concentration.

[S. cerevisiae]

while I understand the science behind it, in practice, the only 2 times (of the more than 80 batches of lager i've made) that I've gotten the banana ester was early in my brewing when I pitched a single smackpack into a 5 gal batch and most recently, when I tried to use the shaken not stirred approach on a vienna.  after 5 weeks of lagering, i dumped the latter this weekend.

Were you the one who attempted to make a large shaken, not stirred starter in not much larger flask?  Or was that Jeffy?   I have never obtained banana ester using the technique.  The only way to get banana ester with underpitching is coupling underpitching with underaeration. 

[S. cerevisiae]

while I understand the science behind it, in practice, the only 2 times (of the more than 80 batches of lager i've made) that I've gotten the banana ester was early in my brewing when I pitched a single smackpack into a 5 gal batch and most recently, when I tried to use the shaken not stirred approach on a vienna.  after 5 weeks of lagering, i dumped the latter this weekend.

Was the posting linked below that batch?  If so, that procedure is not "Shaken, not stirred."

https://www.homebrewersassociation.org/forum/index.php?topic=24308.msg309727#msg309727

[blatz]

No that was the batch previous to the vienna, a pils with mandarina.  That one turned out excellent for me.

For my vienna, I used 2 fresh vials of 830 in 2L 1.040 in a 5L flask.

It took an unusual amount of time to show signs of airlock activity, north of 40 hours (for comparison - the batch you linked I believe was showing signs in around 15 hours.  Perhaps something else came to the party, I'm not sure.

I may try the method again, albeit with a blast of pure O2 rather than shaking.  But I admitted gunshy after having dumped the last batch and having had a lot of success with my "outdated" methods.

[jeffy]

while I understand the science behind it, in practice, the only 2 times (of the more than 80 batches of lager i've made) that I've gotten the banana ester was early in my brewing when I pitched a single smackpack into a 5 gal batch and most recently, when I tried to use the shaken not stirred approach on a vienna.  after 5 weeks of lagering, i dumped the latter this weekend.

Were you the one who attempted to make a large shaken, not stirred starter in not much larger flask?  Or was that Jeffy?   I have never obtained banana ester using the technique.  The only way to get banana ester with underpitching is coupling underpitching with underaeration.

That was me, with a witbier.  No off flavors, but less than satisfactory attenuation.