Author Topic: Ethyl acetate during Kolsch fermentation?  (Read 2140 times)

S. cerevisiae

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #15 on: July 29, 2015, 02:51:33 PM »
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. ;)

More than likely so... If the aroma has changed from nail polish to vinegar, then it would appear that the culture is splitting ethyl acetate back into its constituent compounds; namely, ethanol and acetic acid.  I have personally never experienced what the OP is experiencing.  It will be interesting to read about the final results.

S. cerevisiae

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #16 on: July 29, 2015, 02:52:50 PM »
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".

+1

Fermentation is controlled spoilage.

dfhar

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #17 on: July 29, 2015, 03:31:44 PM »
This one is batch #20.

I dumped the batch this morning. It smelled awful, unlike anything I've made before, and I've used this yeast multiple times. It would have been interesting to see the final outcome, but I have limited fermentation space and haven't brewed anything in months due to the fact that I recently moved. Making another batch is not a big deal - at this point I care more about getting good beer back into my empty pipeline than making an experiment out of this.

Even after a soak in PBW followed by star San, my speidel still smells like vinegar now.
« Last Edit: July 29, 2015, 03:51:05 PM by dfhar »

dfhar

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Re: Ethyl acetate during Kolsch fermentation?
« Reply #18 on: August 19, 2015, 02:00:26 AM »
So I re-brewed the same recipe and fermented in a different vessel. The beer has been kegged a little less than a week now, but also exhibits a slight nail polish remover smell, but no vinegar. The nail polish remover smell was quite a bit stronger when I first kegged the beer, though. I am reasonably certain that this beer is not infected.

I had an extremely vigorous fermentation - from 1.050 down to 1.012 in 4 days. I left the beer in primary another week after FG was reached before kegging. Perhaps overpitching was to blame after all, or maybe it really is stir plate induced stress? This would be the first time I've ever gotten that, and I use my stir plate to make a starter for every batch. I pitched a decanted 1 liter starter of WLP029 into 3.5 gallons of wort and set the regulator to 62. If there was an excess of acetyl CoA rapidly produced early on but not needed for reproduction because either the initial cell density was too high or the malt sugars metabolized too quickly, then I suppose it could esterify into ethyl acetate. I'm just a little shocked, because I often hear about people getting away with large pitch rates of WLP029 and getting a cleaner beer, not an estery one.

The 15 or so batches prior to this one have been lagers that turned out great, including one that got a gold medal in a BJCP comp. I guess I just got used to making big starters.

I'll likely try to re-brew this recipe again soon, perhaps with a smaller pitch rate and a slower setting on my stir plate.
« Last Edit: August 19, 2015, 02:34:26 AM by dfhar »