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Author Topic: DMS appearing after kegging?  (Read 756 times)

Offline cassidymiller

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DMS appearing after kegging?
« on: October 11, 2022, 10:46:40 am »
I'm at a little bit of a loss, looking for some insight.  I brewed this in the spring and had to dump the batch.  Rebrewed it late summer, this time without using fermcap in the boil (I was concerned maybe it prevented the DMS precursors from boiling off).  Ended up with the same result, a totally vegetal and undrinkable beer.

Pretty basic czech pilsner recipe, 10 lbs bohemian pilsner malt, 8oz saas pitched in equal amounts at 60, 30, 10, and 0 during a 90 minute boil (vigorous boil, I'm in Denver and lose ~1 gal/hr to evap).  Chilled with a counterflow chiller and when down to temp pitched with a 2L starter of WLP800.  O.G. 1.050.  Fermented at 52 for 2 weeks to hit 1.008.  Raised to 68, held for 3 days (SS brew bucket with a glycol chiller for temp control).  Tested for diacetyl and it was fine.  No DMS present at all.  Dropped 1-2 degrees per day to reach 38 degrees and held there for 2 weeks.  Tasted at kegging and it was great. 

Both batches tasted fine at kegging but by the time they were forced carbonated they were undrinkable, with the hops completely overwhelmed by a vegetal creamed corn taste.  I clean the keg with oxyclean free, hit with a good hot water rinse, then fill it with sanitizer solution, let it sit for a period, and purge with CO2.  Tap lines were completely disassembled and cleaned for each batch (I actually replaced the lines completely for this last batch).  I've never had a problem with DMS before and I'm not even sure what to do different at this point.

I should add I'm using Denver tap water, treating it with a campden tablet, and adding lactic acid during the mash to hit a pH of 5.2 to 5.3. 

« Last Edit: October 11, 2022, 11:21:45 am by cassidymiller »

Offline mabrungard

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Re: DMS appearing after kegging?
« Reply #1 on: October 12, 2022, 01:09:37 pm »
You are correct to boil for 90 minutes at your elevation to enhance SMM conversion and DMS volatilization.  The lower boiling temperature at that elevation, reduces the rate of conversion of SMM to DMS and more time is required.  However, you don't have to boil open-topped for that entire period.  Simmering the wort in a covered kettle for about the first half of that period and then uncovering and boiling vigorously for the second half does avoid the excessive loss by evaporation.

Pils malt is full of SMM and the potential for DMS in resulting brews is higher when using large percentage (100% in this case).  One variable that you didn't mention is the time duration between end of boiling and getting your wort chilled to under 185F.  That's the period when any remaining SMM might convert to DMS.  But the indication that you checked for DMS after fermentation seems to negate that this occurred.  My concern is that there is so much flavor components remaining in that freshly fermented beer, that you might not be able to detect the subtle DMS notes that might have been there.  After lagering, those flavor components have been settled out of the beer and DMS could be more notable. 

Another cause of DMS in beer is an infection.  Did that beer clarify well?  I'd expect that it would be unlikely that those spoiling organisms could prosper at lagering temperature.   
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Offline kramerog

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Re: DMS appearing after kegging?
« Reply #2 on: October 18, 2022, 04:22:52 pm »
Cassidy, are you using floor malted Bohemian Pilsener malt? From the same bag each time? Apparently there is a wider variability with floor malting.  See last message at https://discussions.probrewer.com/forum/probrewer-message-board/brewery-operations/malt-q-a-available-for-sponsorship/43018-dms-from-weyermann. You might not have the problem with regular Bo Pils malt.

Also, Scott Janish, who is an author and now a commercial brewer, did a literature review for DMS at
http://scottjanish.com/how-to-prevent-dms-in-beer.

Offline cassidymiller

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Re: DMS appearing after kegging?
« Reply #3 on: October 22, 2022, 09:12:29 pm »
Cassidy, are you using floor malted Bohemian Pilsener malt? From the same bag each time? Apparently there is a wider variability with floor malting.  See last message at https://discussions.probrewer.com/forum/probrewer-message-board/brewery-operations/malt-q-a-available-for-sponsorship/43018-dms-from-weyermann. You might not have the problem with regular Bo Pils malt.

Also, Scott Janish, who is an author and now a commercial brewer, did a literature review for DMS at
http://scottjanish.com/how-to-prevent-dms-in-beer.

It's just the regular Weyermann Bohemian Pilsner malt from the Brew Hut, thought I was looking for the floor malted.  Maybe I'll pick up some Root Shoot Pils and see if I get a different outcome.