DMS damage control

Sure sounds like DMS.

ETA: And yes you have to be old to remember Rolling Rock. At least the original version brewed in Latrobe. It was the one beer on the planet that I refused to drink under any circumstances once I knew what it tasted like. I think I can still taste it.

 

To clarify, the DMS came from the Pils DME that was cooled slowly and then pitched with the yogurt at low cell counts leading to a less than rigorous fermentation to drive off the DMS. My understanding is that yeast/bacteria don't create DMS, it is the conversion of SMM to DMS that causes it, which it does on its own. To avoid DMS you want to do a full vigorous boil uncovered and then quickly chill to pitching temps, pitch with healthy yeast at adequate cell counts, and have it active and churning within 18-24 at the latest. Pils malt is higher in DMS than Pale/Vienna/Munich Malts. If Pils is used, no adequate boil, no quick chill, and under pitched, then you are asking for DMS.

 

The yeast derived sulfur compounds in that statement are the sulfur dioxide and hydrogen sulfide. The DMS is malt derived. Mercaptan is hop derived (skunk). The SMM is from the malt and converted to DMS. DMS can oxidize and not have an expressive note (DMSO) but yeast has the ability to remove the oxidation from the DMSO turning it back into DMS. In this case, DMS is present from the malt and the yeast brings it back into play, but it never created it.

 

“Pils malt is higher in DMS than Pale/Vienna/Munich Malts.”

Justin, you meant to state that Pils Malt is higher in SMM in the above sentence.

The pathway to DMS is that the SMM is ‘converted’ to DMS via heating. The majority of SMM -> DMS occurs during mashing but some SMM -> DMS occurs during the boil as well. The good news is that DMS is very volatile so a vigorous boil will dissipate most of the DMS.

The ‘bad news’ relative to DMSO is that it is more stable so less of it is dissipated during the boil.

Cheers!

 

All true. And any remaining SMM that is not converted to DMS during the boil can be converted while the wort is being cooled. (The cooling process doesn't cause it per se, but the elevated temperatures do.)

 

Yes, yes I did. Or Pils malt has a higher potential for DMS than... or Pils malt is higher in DMS precursors than...

 

So here's the thing. White and Zainasheff state that DMSO is malt-derived but is not affected by the boil. This means that the normal precautions that brewers take (vigorous, uncovered boil, rapid cool-down) are presumably ineffective at controlling DMSO. White and Zainasheff go on to suggest that DMSO can be converted to DMS by the yeast. Meanwhile, in How to Brew, John Palmer notes that DMS is a flaw that can be caused by bacterial infection. (I don't have the book in front of me, but I think he states this in the chapter on troubleshooting off-flavors.) Perhaps he means that bacteria, like yeast, can convert DMSO to DMS (though he does not spell this out).

All of this suggests that there are two distinct channels through which DMS can become a problem in beer: (1) SMM + heat, in the absence of a mechanism to drive the resulting DMS away, and (2) DMSO + microbial reduction to DMS.

Channel 1 is well-understood in the homebrewing community, and most of us know that when we are using pilsner malt we should do 90-minute uncovered boils and rapidly chill the wort to pitching temperature. (Although there are some puzzling aspects of channel 1. For instance, why doesn't @OldSock experience DMS with his no-boil berliner weisse beers, which would seem to be custom-designed for channel-1 DMS production? The answer may be that he ages his berliner weisse beers long enough and warm enough for the DMS to evaporate away.)

Channel 2, though, can't be managed in the same way as channel 1, and it is a channel that I was unaware of until today. (By the way, @jbakajust1, I think it's possible that your yogurt/DMS experience worked through channel 2, or through a combination of channels 1 and 2, and not solely through channel 1.) I don't understand what to do to avoid DMS production through channel 2. Is it a matter of avoiding pilsner malt? That would be unfortunate. Maintaining a healthy fermentation? If @FeDUBBELFIST's experience is representative, a healthy fermentation may not be a guarantee of avoiding channel-2 DMS.

Maybe this is a rare enough occurrence that we can ignore channel 2, as I have been doing up until today. But I would certainly like to know more about it!

 

Below is from Beersmith:

“During fermentation, CO2 bubbles actually help remove from DMS from the beer. More vigorous ale yeasts tend to produce lower DMS levels. Also different strains of yeast do tend to produce DMS during fermentation primarily by converting DMSO (which does not boil off) to DMS. Lager yeasts and yeasts fermented at lower temperatures tend to have higher DMS production. Certain wild yeasts and bacteria can create high levels of DMS as well.”

http://beersmith.com/blog/2012/04/10/dimethyl-sulfides-dms-in-home-brewed-beer/

Given that @FeDUBBELFIST brewed a Tripel the thought from the above is that the vigorous ale fermentation should have outgassed the DMS produced by DMSO/yeast.

Cheers!

 

dude is DOOMED

 

I brewed an all grain AG24 Oktoberfest and resulted in the same problem with high DMS smell and taste rather than dump it after fermentation for 2 weeks and lagering for 5 weeks I decided to try placing cooper foil into my keg I let this set for a week at 55F and the carbonated ,it got rid of most but not all but I have a very high taste ability . This use of copper is use in wine making for the same purpose. And the old Beer makers used copper fermenter to battle against this ...

 

Copper works for sulfur compounds in general.

 

This post has sparked some curiosity in me, and I've been doing some reading.

Some DMS is known to be in extract. We know this, and it's another reason why we do boils.

S. cerevisiae does have the ability to convert DMSO into DMS by use of an enzyme: methionine sulfoxide.

Someone suggested a 90 minute boil. That won't do anything for you as the boiling point for DMSO is 372 F/ 189 C. Those temperatures are higher than that which water can boil (once water boils, crank the heat up as much as you like it just boils more vigorously, the temp does not increase), so DMSO can not be boiled off. DMS should be boiled off fairly quickly, so boiling for a longer time would not benefit that.

This article was a good read. SMM is a precursor for DMS and is more prevalent in lightly kilned malts. This is because SMM is more stable and will survive the boil. Darker kilned malts however will have more SMM reduced to DMS during the kilning process, but that will get boiled off during the brewing process. What is interesting is that SMM is readily converted to DMS at about 140 F. This is why it is important to rapidly cool the wort post boil. But I wonder, what if a wort was held at 140 for a length of time to have SMM converted to DMS, and then it was re-boiled to expel the DMS. So, doing 2 boils essentially. Or if you could steep grains at a lower temp for a greater SMM -> DMM conversion, and then boil off the DMS. It also made a mention about how copper has historically been used to control sulfur compounds, but who knows if this was intentional or coincidence (maybe this would be a good excuse for me to get a worth chiller Or just use some copper wire in the brew kettle or carboy).

I've seen several articles correlating the prevalence of DMS and lagers. I havn't seen the causation though. I did read an article about how some stresses will activate sulphur metabolic pathways in some strains of yeast. Be it hyperosmolarity, cold, ethanol, excess acetaldehyde .

Several strains of bacteria can produce DMS, hydrogen sulfide, and other undesirables. This is why sanitation is so important.

 

It's my understanding that SMM is being converted to DMS all throughout the boil. There is even some SMM still being converted to DMS after the boil. So the longer boil allows more DMS to be boiled away.

 

I agree with you to some extent. It's my understanding the a shit tun more DMS is boiled off in 90 minutes than 60 minutes, however a 60 minute boil removes enough to get the overall DMS level below the perception threshold of most consumers.

 

I didn't see anything in the literature about quantifying concentrations, or a comparative analysis of pre vs post boil of 60 minute boils, to 90 minute boils. It would make for a good study. I just didn't see any data on it. A longer boil has the most potential to be more beneficial for lighter malted grains. Something to consider.

 

Pilsner malt does indeed have a bit more SMM in it than 2 row, but 6 row has way more in it than pilsner malt. Darker malts have the potential for quite a bit too, but the flavors they bring to the beer mask it more than paler malts.

According to Brad Smith, the half-life for DMS is 40 minutes, so half of the DMS will be boiled off in a 40 minute vigorous boil. That means a 60 minute boil gets rid of 64.7% of the DMS and a 90 minute boil rids us of 79% of the DMS.

Rapid chill time post boil and preventing infections in your beer are also necessary to prevent the reformation of DMS in your final product. For the former, Smith claims that the DMS can increase up to 30% in just an hour post boil. This is quite significant in commercial settings where it can take that long to transfer the batch of wort through the heat exchanger. It's also significant in homebrew settings when brewers do extended hop stands post boil.