Author Topic: Ethyl acetate during Kolsch fermentation?  (Read 1067 times)

dfhar

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Ethyl acetate during Kolsch fermentation?
« on: July 28, 2015, 03:01:51 PM »
I brewed a 3.5 gallon batch of Kolsch this past Saturday, pitching a 1 liter starter of WLP029 at 60 degrees and fermenting at 62. I pulled a sample last night to keep on hand for a fast ferment test - 2 days after pitching, the gravity had gone from 1.052 down to 1.020, but I noticed a very strong nail polish remover smell in the sample, which I believe is caused by ethyl acetate, although I've never had this happen before.

Is it common for ethyl acetate to show up like this during fermentation? Is it something that will eventually be cleaned up by the yeast? I'm at a loss here - I pitched a good amount of fresh yeast into cold, mix-stir aerated wort and fermented on the cool side. How did I end up making nail polish remover?
« Last Edit: July 28, 2015, 03:05:06 PM by dfhar »

Offline toby

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #1 on: July 28, 2015, 03:35:10 PM »
Solventy aromas can be from too hot a fermentation temperature (various fusels), but that shouldn't be an issue at 62F.  1L of a starter for a 3.5 gallon batch is also on the high side for an ale.  If it is ethyl acetate, that's going to be formed from ethanol and acetic acid which means a potential acetobacter infection.  I definitely wouldn't dump it yet, but monitor it.  Unless you're super sensitive to it, it's not a normal byproduct.

Offline kramerog

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #2 on: July 28, 2015, 04:28:04 PM »
I get ethyl acetate when making sour beers with lacto in an open fermentation.  I do closed fermentations now.

Offline hopfenundmalz

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #3 on: July 28, 2015, 04:58:39 PM »
This might help. It is from acetyl CoA and ethanol, so is in all beers. Threshold level is high.

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Offline kramerog

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #4 on: July 28, 2015, 05:06:43 PM »
It might be caused by too big a pitch.  The theory is that acetyl CoA is used for growing yeast, but that if it is not used to grow yeast then it will make esters.

dfhar

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #5 on: July 28, 2015, 05:36:49 PM »
Thanks for the replies, everyone.

www.yeastcalculator.com says I need 170 billion cells for a 3.5 gallon 1.052 hybrid ferment. Using Kai Troester's stir plate model, a 1 liter starter is predicted to give about 222 billion cells. This doesn't sound like a significant overpitch, especially when Jamil's model only predicts 187 billion cells for a 1L starter.

I'm wondering if it's an acetobacter infection, although I've never had one before and my kitchen is damn near spotless with no fruit flies to be found. Everything gets a soak in PBW followed by a hot water rinse and then a soak in star-san before I rack from kettle to fermenter.

I'm wondering if too much kettle trub made it into the fermenter? I've been a bit lazy about that lately, racking everything except the thick sludge at the very bottom. I've done this on several batches now without issue, but maybe my luck has run out.

I'll give the beer another week in the fermenter and see what happens. After that I'll do a 180 F hot water sterilization of my equipment and try another brew.

dfhar

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #6 on: July 28, 2015, 11:48:40 PM »
I just got home and got a whiff of vinegar from the airlock. I think it's acetobacter. First time for everything, I guess  :-[

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #7 on: July 29, 2015, 12:07:23 AM »
I just got home and got a whiff of vinegar from the airlock. I think it's acetobacter. First time for everything, I guess  :-[
Yeah, condolences.

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #8 on: July 29, 2015, 11:40:12 AM »
I just got home and got a whiff of vinegar from the airlock. I think it's acetobacter. First time for everything, I guess  :-[

I'd still let it bride. "wiffing" from the airlock is a very poor sensory analysis technique.

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #9 on: July 29, 2015, 01:31:58 PM »
It might be caused by too big a pitch.  The theory is that acetyl CoA is used for growing yeast, but that if it is not used to grow yeast then it will make esters.

Acetyl-CoA is used for more than growth.  It is a precursor to energy.



In my humble opinion (an it's just that),  in the absence of a confirmed infection, what you are experiencing is the result of stir plate-induced stress.  I have mentioned many times that stir plates subject the cells to shear stress, which is why I no longer use a stir plate.

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #10 on: July 29, 2015, 01:42:23 PM »
It might be caused by too big a pitch.  The theory is that acetyl CoA is used for growing yeast, but that if it is not used to grow yeast then it will make esters.

Acetyl-CoA is used for more than growth.  It is a precursor to energy.



In my humble opinion (an it's just that),  in the absence of a confirmed infection, what you are experiencing is the result of stir plate-induced stress.  I have mentioned many times that stir plates subject the cells to shear stress, which is why I no longer use a stir plate.

I say he is still jumping to conclusions. He seems to be basing his impressions off of a sample pulled for forced fermentation and not a finished beer. The other impression is off an "air lock" sniff. Neither of these things are very reliable forms of analyzing a finished beer. Now you are jumping to conclusions too, Mark. ;)

dfhar

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #11 on: July 29, 2015, 02:16:38 PM »
The whole fermentation freezer smells like a sour beer now. Can that really happen that fast (3-4 days)?
« Last Edit: July 29, 2015, 02:20:06 PM by dfhar »

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #12 on: July 29, 2015, 02:27:23 PM »

In my humble opinion (an it's just that),  in the absence of a confirmed infection, what you are experiencing is the result of stir plateviolent shaking-induced stress.  I have mentioned many times that stir plates subject the cells to shear stress, which is why I no longer use a stir plate.
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Offline reverseapachemaster

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #13 on: July 29, 2015, 02:35:03 PM »
I think you're jumping the gun with a diagnosis of a problem in the midst of fermentation. Let the beer finish fermenting before you declare it a disaster.
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Re: Ethyl acetate during Kolsch fermentation?
« Reply #14 on: July 29, 2015, 02:37:00 PM »
I think you're jumping the gun with a diagnosis of a problem in the midst of fermentation. Let the beer finish fermenting before you declare it a disaster.

Exactly! How many batches do you have under your belt? Fermentation can throw some funky, including sour, aromas. You can sort of think of fermentation as a form of "controlled rotting".