Can yeast produce DMS?

[JHulen]

I made a blonde ale with Pilsner malt, and it has a heavy off flavor that I think tastes and smells like canned corn. My palate isn’t trained enough to know exactly what it is, but I really get a corn flavor and aroma out of it. Kind of like that weird flavor in BMC but amplified. Is this DMS? At first I thought it was esters, but the beer is clean in the finish.

I know Pilsner malt is susceptible to DMS, so I did a 90 minute boil, fermented at 67 degrees (controlled) , and oxygenated the wort prior to pitching. I’ve brewed this recipe before and this is the first time encountering this. The big variable is that I pitched US-05 and not WLP001 like I always had before. I have another batch of the same recipe ready to bottle now, and it was fermented with WLP-001. I’m interested to see if this batch will come out normal like the ones before.

 

[NobleNewt]

I can't remember, but I feel as though there was a Brulosophy podcast where he talked about off flavors from improper pitch rates and the like. Take it for what it's worth, but he believes that a healthy yeast pitch will eliminate most off flavors including DMS in the finished beer.

I subscribe to that as well, but only because I know how critical the yeast is in flavor creation.

Depending on who you listen to and what you read, there's been some folks out there that have largely debunked how much DMS affects homebrew with modern malts and boiling techniques. Not to say it isn't a thing, but everyone seems to have a differing opinion on the matter.

Do you typically make a starter? What is your pitch rate?

 

[Lefou]

I'd hazard a guess and agree with you about the yeast strain reacting with the Pilsner malt during fermentation. After a few brews I made the switch to liquid yeasts because I wanted certain characters within the beer and to get a perceived reduction in the lag time for a strong fermentation using quick yeast starters.
I've used both yeasts with beer but never had any creamed corn aromas, but then again, my Pilsner malts may be very different from the ones you used. My Pilsner malts are usually Avangard, Briess two row, or Dingemans light Pilsner malt.

 

[NobleNewt]

I'd hazard a guess and agree with you about the yeast strain reacting with the Pilsner malt during fermentation. After a few brews I made the switch to liquid yeasts because I wanted certain characters within the beer and to get a perceived reduction in the lag time for a strong fermentation using quick yeast starters.
I've used both yeasts with beer but never had any creamed corn aromas, but then again, my Pilsner malts may be very different from the ones you used. My Pilsner malts are usually Avangard, Briess two row, or Dingemans light Pilsner malt.

I tend to agree with you on the lag time aspect. That seems to be the biggest reason I’ve seen for DMS issues is that the wort sits generates? DMS before active fermentation begins.

Also, it seems as though some people are far more sensitive to DMS flavors and aromas than others. Brulosophy did do a lid-on during the boil experiment, but found that there wasn’t any statistical significance in the perceived presence of DMS.

I’m in the same boat as the OP in that I brewed a Kolsch-ish beer with Vienna as my base malt and cracked my kettle lid instead of doing a lid-off boil to try to control my boil-off rate. I then pitched a totally dry packet of US-05 into my 3.5 gallon batch, so we’ll see what happens. I know my pitch was sufficient, but because it was a dry yeast and wasn’t active at the time of pitching I wonder if off flavors may develop.

 

[NobleNewt]

Here's a BeerSmith link about DMS that might be helpful in troubleshooting: http://beersmith.com/blog/2012/04/10/dimethyl-sulfides-dms-in-home-brewed-beer/

 

[JHulen]

I pitched 1 packet into 5 gallons of 1.046 wort. The fermentation took off quickly. FG ended at 1.008

 

[RPh_Guy]

Contaminanting microbes can potentially produce DMS.

 

[JHulen]

Contaminanting microbes can potentially produce DMS.

That could be it. I don’t know how because I don’t slack on that front, never had an infected batch. I’m not 100% sure it’s DMS. I just know DMS tastes and smells of corn/vegetables and that’s what I’m getting on my palate.

 

[Vale71]

The answer to the topic title is no, yeast can neither produce nor reduce DMS as it is in no way part of their metabolism. Vigorous fermentation can help scrub some DMS from the wort through the rising CO2 but this is due to the CO2 only regardless of the yeast. As a metter of fact CO2 scrubbing is used at the industrial level to remove off flavors from beverages and from beer as well. Since your beer is done fermenting you cannot expect any improvement in that regard unfortunately.

 

[mabrungard]

I don’t have the reference, but I do recall that some yeast strains can produce DMS. But given the high Pils content, that is the more likely source.

 

[kh54s10]

Two things I think I would eliminate from the cause. Choice of yeast (essentially the same) and lag time. In my experience lag times with dry yeasts are not significantly longer than with liquid yeasts. In about 90% of my brews, I have pitched the yeast late in the afternoon and had active fermentation when I got up the next day, liquid or dry and with the dry - re-hydrated or sprinkled.

 

[Vale71]

Are you sure you're not thinking of diacetyl? Or possibly diethylsulfide which causes a similar but different off-flavor usually described as onion-like. Brewer's yeast cannot as a rule produce methyl esters as there is no methanol in beer therefore yeast has no source for the methyl group.

 

[mediant]

Brewing yeast enzymatically reduce DMSO to DMS during fermentation. This process depends on many variables, among them: yeast strain (ale yeast produce more DMS than lager), pH (higher pH favors DMS), temperature, wort gravity.
If your brewing is done right (long boil, rapid wort cooling), then most likely the malt you used was produced with higher than usual DMS precursor levels - SMM and DMSO. These are strongly influenced by barley variety, germinating conditions, kilning temperature and so on. Just switch to other brand, if possible.