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Thread: DMS formation post packaging

  1. #1
    Join Date
    Dec 2013
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    Madison, WI, USA
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    DMS formation post packaging

    Hey all,
    We brew a classic German Style Pilsner and we've been having an issue with DMS formation after transfer to brite/packaging. The first batch we brewed we used biofine as a clarifying agent and noticed DMS formation a few days after transfer the the brite tank. I was able to successfully scrub most of this DMS out by bubbling CO2 into the brite to degass and then re-carbonate the beer. This first batch seemed to still have small traces of DMS in the brite but after a few weeks of it being in kegs it disappated and tasted clean and wonderful. One the second run of this beer I tried a few things to further reduce DMS. I lengthened our boil from 90 minutes to 100 minutes and let the fermentation go in to free rise at approximately the half-way point in the fermentation. All of this was done in an effort to help scrub out more SMS/DMS. We then filtered the beer and it was tasting fine out of the filter. I only noticed DMS after putting the beer on tap. Due to the fact that I'm only perceiving this DMS after transfer out of the FV or packaging, it seems likely that we have a fair amout of DMSO left in our Pilsner prior to transfer/packaging. Does anyone have any suggestions or info on how to further reduce DMSO or how DMSO is formed in the first place? Here's some info on the beer to help with diagnosing the issue.

    Grist:
    95% Weyermann Pils
    5% Weyermann Cara-hell

    Hop Schedule:
    15 BU worth of Magnum @ 90 min
    .5#/bbl of Tettnang at 5min
    .75#/bbl of Hersbrucker in WP

    Boil:
    100 Min total boil
    *We have a low pressure boiler so it's hard to maintain an even and consistent boil but I'm boiling as hard as I can without having constant boil overs

    Fermentation: BSI Czech 34/70 Lager Yeast
    Start Fermentation at 48 F
    Put into free rise approximately half way through fermentation
    Give beer diacetyl rest at least two days after reaching TG
    Slowly cool to 32 F over the course of three days.

    Should I boost my boil to two hours? Am I introducing higher levels of DMSO with the heavy late hop additions? Any help or suggestions are much appreciated. Cheers!

  2. #2
    Join Date
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    You don't say how long you stand in whirlpool, or how long the transfer to FV. Long stand / transfer times can lead to greater development of DMS from the pre-cursor.

    Another possibility is infection with zymomonas or Obesum bacterium proteous, or Enterobacter aerogenes
    dick

  3. #3
    Join Date
    May 2012
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    Theres a few possibilities:
    1. Is an improper boil which fails to reduce SMM to DMS, and then to volatize it.
    2. Infection

    You would taste the DMS in the wort pre-fermentation. Yeast can convert DMSO into DMS, it is not that big of a conversion. The other possibility, but again if you dont taste DMS in the wort post boil it shouldn't really be a problem. SMM can remain, some malts have more of it in my experience the Weyermann malts do, and this will convert at temperatures above 80C easily into DMS. But again, unless you are knocking out into your FV at that temp, you shouldnt see an increase. Its possibly an infection as well, which you should plate this beer on media selective for the possible culprits.

    Some solutions:
    1. Plate for infections
    2. Copper: We use a copper pipe as a dipstick in our kettle for determining when we are at our full volume. Copper reduces DMS rapidly. The dynamics of the reaction say that if there is a drop in the products, then the reaction will shift to produce more until it is in balance. So starting to reduce the DMS before the boil will help. I know of a few breweries who also run the wort through a section of copper pipe on the way to the FV to mop anything up.
    3. Change malts. Look for some analysis of the malts to see what kind of SMM and DMSO levels you can find. Its been a while since I have looked at Weyermann Malt analyses, so I don't remember if they report DMS-P or anything. But you can certainly try different malts to see what difference it makes.

    I would attack this starting at 1 and going to 3, sort of the least invasive to most invasive processes for your recipes.

  4. #4
    Join Date
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    Cincinnati, OH
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    Quote Originally Posted by jebzter View Post
    Theres a few possibilities:
    1. Is an improper boil which fails to reduce SMM to DMS, and then to volatize it.
    2. Infection
    I would expand as this:

    1 - SSM
    2 - DMSO

    These guys have it down. At a 100 min boil you should have converted and volatized about 87.5% of all DMS from SMM. Half-life of the SMM-DMS evaporation is about 32-38 mins at boil (100*C). Depends on pH. This doesn't even require a large volume of evaporation either. As little as 3% evaporation is sufficient. You should be sufficiently removing all concerns of SMM based DMS with your boil.

    DMSO (and others) are not readily converted during boil. DMSO specifically volatizes at 189*C. It can be converted to free DMS during the metabolic process of some yeast strains and some bacteria. The enzyme responsible is DMSO reductase. Malt processing has a large impact on these precursor compounds.

    If you are not seeing the DMS post boil, then that suggests you have indeed volatized all present free DMS up to that point. Formation can occur during whirlpool or rest as Dick mentions, but this tends to happen with SMM-DMS conversion and not DMSO-DMS. Test for the DMS after boil, and again at end of Knock Out.

    My guess based upon your descriptions is that you are having DMSO carryover that is not being converted and volatized. The DMSO is then being converted by the yeast into free DMS late after packaging. This can happen after passing QA/QC specs and be a big surprise.

    DMSO can be introduced by way of hops (dry hopping) or may carry directly from the malt through mashing and boiling. Fermentation gasses will scrub some free DMS, but if it is still DMSO, it will remain behind. Higher gravity wort, higher pH wort, and colder temperatures increase likelihood of DMSO-DMS conversion by yeast/bacteria. Some strains are more prone than others to convert.

  5. #5
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    But I guess to answer the actual post, I would suggest avoiding the DMSO conversion.

    I would either change malt supply to reduce the initial DMSO present from malt, or I would change the yeast in favor of one that does not convert DMSO to free DMS as easily.

  6. #6
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    Dec 2013
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    Quote Originally Posted by UnFermentable View Post
    But I guess to answer the actual post, I would suggest avoiding the DMSO conversion.

    I would either change malt supply to reduce the initial DMSO present from malt, or I would change the yeast in favor of one that does not convert DMSO to free DMS as easily.
    Thanks for the tips! I'm pretty confident that our process is adequately removing DMS in the boil. We whirlpool for 5 min, rest for 20 and cool in 35. This leaves me to believe that it is almost certainly DMSO conversion. We brewed an even lighter lager than our Pils and it turned out beautiful and free of DMS. Infection doesn't seem likely as this problem has been unique to this one brand and has not carried over into beers that were pitched with yeast from that tank. Has anyone experienced a vegetal character similar to DMS as a result of over hopping? Or is it more plausible that this is actually DMS resulting from an excess of DMSO brought on by the hops?

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