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How quickly does DMS build up?

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Myllymaki

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Post Sat Jan 02, 2010 12:52 am

How quickly does DMS build up?

I made a 100% pilsner malt beer today, 90 minute boil, and used my trusty immersion chiller to cool the wort. The immersion chiller is usually very fast, but today one of the hoses I hooked up to the chiller had a plug of ice frozen inside and it took me maybe 5-10 minutes to get it flowing after I shut the burner off. After that it chilled very quickly. I will obviously see how it turns out later, but does anyone have any experience regarding how long it takes hot wort sitting there to build up detectible amounts of DMS? I would think that 5-10 minutes is pretty short (and that people using CF chillers would have part of their wort sitting in the kettle that long before it is chilled). Any input appreciated.
Last edited by Myllymaki on Sat Jan 02, 2010 2:48 am, edited 1 time in total.
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Bonzer

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Post Sat Jan 02, 2010 1:02 am

Re: How quickly does DMS build up?

After 90 minutes of boiling, you won't have any DMS.
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rebuiltcellars

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Post Sat Jan 02, 2010 1:09 am

Re: How quickly does DMS build up?

There is very little after a 90 minute boil, and if you boiled that long I wouldn't worry at all. In fact, with only a 5 minute wait I wouldn't worry at all either. The other factor which should put your mind at ease is I'm guessing you didn't put the cover on the kettle. Leaving the cover off would allow any DMS that forms to disperse even if you boiled for a shorter time or waited longer before chilling.
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Myllymaki

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Post Sat Jan 02, 2010 3:02 am

Re: How quickly does DMS build up?

Thanks for the replies. I did some more reading after posting the question and found information about the 45 minute half-life of DMS (so a 90 minute boil removes ABOUT 3/4 of the DMS). With that reduction and the pretty brief hot-stand before I got the chiller working, it sounds like it should be fine.
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Hampshirebrewer

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Post Sat Jan 02, 2010 9:34 am

Re: How quickly does DMS build up?

My understanding is that DMS is driven off by the boil. An uncovered 90-minute boil is best for this.

However, DMS can reform during cooling in the 170 F to 110 F window (my temps may be off here a little; science is OK but beer is better).

So I do let my pilsners sit covered for 15 minutes after end of boil at 190+ before chilling with my IC.

Then I chill. I center a short dowel under the pot so I can rock it for the 5-10 minutes it takes to cool under 110F. This seems sufficient to circulate the wort to improve the efficiency of the chiller.

So if you had a 10 minute delay before chilling could begin owing to an ice plug, you should have no worries.

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narcout

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Post Sat Jan 02, 2010 12:49 pm

Re: How quickly does DMS build up?

Hampshirebrewer wrote:However, DMS can reform during cooling in the 170 F to 110 F window (my temps may be off here a little; science is OK but beer is better).


I think DMS will be produced as long as the wort is above 140 degrees, provided there is sufficient SMM.

Hampshirebrewer wrote:So I do let my pilsners sit covered for 15 minutes after end of boil at 190+ before chilling with my IC.


This seems counterintuitive to me. While the wort is still hot enough that SMM is being reduced to DMS, you want it to be able to escape the wort through vaporization. If you have your kettle covered during this period it is instead going to condense on the lid and drip back into the wort.
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rebuiltcellars

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Post Sat Jan 02, 2010 1:30 pm

Re: How quickly does DMS build up?

narcout wrote:
Hampshirebrewer wrote:However, DMS can reform during cooling in the 170 F to 110 F window (my temps may be off here a little; science is OK but beer is better).


I think DMS will be produced as long as the wort is above 140 degrees, provided there is sufficient SMM.

Hampshirebrewer wrote:So I do let my pilsners sit covered for 15 minutes after end of boil at 190+ before chilling with my IC.


This seems counterintuitive to me. While the wort is still hot enough that SMM is being reduced to DMS, you want it to be able to escape the wort through vaporization. If you have your kettle covered during this period it is instead going to condense on the lid and drip back into the wort.


Hampshirebrewer, listen to narcout. He's on the money with this. To eliminate DMS you want to boil as long as you can, cool as fast as you can, and make sure to keep the kettle uncovered until the wort is below 140.
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Hampshirebrewer

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Post Sat Jan 02, 2010 4:16 pm

Re: How quickly does DMS build up?

If I can't locate my source information before mid January, then I won't hop stand my next pilsner.

If I find the source information I'll post it.

You may have found a fault in my process. Thank you for noting it. I'll be back with my research hopefully soon.

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Hampshirebrewer

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Post Sat Jan 02, 2010 9:21 pm

Re: How quickly does DMS build up?

I have found a mix of information.

Most texts I have barely mention dimethyl sulfide (DMS) except to chill the wort as quickly as possible and to boil the wort uncovered (books by Palmer & Miller; articles by Steve Parkes in BYO)

DMS formed in the kettle is driven off by an uncovered, rolling boil. A 90-minute boil is preferred. Precursors are still in the wort waiting for time and kettle temperatures to allow them to form DMS.

The strongest science books I have are by George Fix. He notes that lightly kilned and higher protein content malts, particularly pilsener and 6-row malts respectively contain higher levels of S-methyl methionine (SMM) which during heating can break down into DMS. In Principles of Brewing Science (PBS) he reports that shorter cooling times reduce SMM and consequently DMS in the finished beer. His mathematical examples make a good case to reduce a 60-minute chilling time to 30 minutes by doubling the reduction of DMS.

It also appears that pale malts kilning is such that DMS is not a worry for the brewer, and he states that DMS in ales is likely caused by contamination.

Back to lager brewing. Fix in PBS notes that up to 50% of SMM and DMS is removed by CO2 during fermentation (I think this helps explain the sulfur smell from fermenting lagers) and that brewers take extra steps to reduce SMM residuals including spraying hot wort with nitrogen gas and,

"Another procedure that is used for reducing (as opposed to eliminating) SMM and DMS levels consists of holding wort at 90-95C, allowing for maximum ventilation." He then goes on to note an equation for determining the holding time.

Fix in An Analysis of Brewing Techniques simplifies his statement to this:

"Also, holding the worts just under 212F (100C) for fifteen minutes after the boil is another way to achieve low DMS levels."

Greg Noonan, in New Brewing Lager Beer, allows for hops and trub to settle for 10-15 minutes and then force-cooling the wort quickly (15-45 minutes) to give a more complete break than slow or passive attempering, and reducing DMS development.

What I get from this is that a 15-minute pause before chilling may help reduce DMS if the temperature is close to boiling. And that I should modify my practice to not have the lid on the pot during this phase to allow precursors to continue to evaporate (right on down to 140 or even 110F). Thankfully there are no flying insects here in Vermont during lager season.

I will keep looking for the source of the 110 to 170F range for DMS production.
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narcout

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Post Sun Jan 03, 2010 12:40 pm

Re: How quickly does DMS build up?

My experience has been that even with a grainbill consisting of 100% pilsner malt, a 90 minute boil is sufficient to reduce DMS without an additional hot rest.
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Karl750

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Post Sun Jan 03, 2010 4:40 pm

Re: How quickly does DMS build up?

narcout wrote:My experience has been that even with a grainbill consisting of 100% pilsner malt, a 90 minute boil is sufficient to reduce DMS without an additional hot rest.

+1

90-100 minute boils and a quick chill have allowed me to avoid DMS every time I've used pils malt.
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rebuiltcellars

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Post Mon Jan 04, 2010 2:38 am

Re: How quickly does DMS build up?

narcout wrote:My experience has been that even with a grainbill consisting of 100% pilsner malt, a 90 minute boil is sufficient to reduce DMS without an additional hot rest.


-1 While everything I've read says you are right, the only time I've actually had a problem with DMS in a brew was with a 90% pilsner malt that I boiled for 120 minutes. The problem was I was still cooling in a sink of cold water at the time and it took a long time (with the lid on) to get the wort cooled below 140. It wasn't overpowering, but it was present if you looked for it and it was the reason I finally decided to get a chiller.
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drf255

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Post Mon Jan 04, 2010 4:31 am

Re: How quickly does DMS build up?

I'm most likely going to use the Australian/Onthekeg's method (hot kegging my wort and letting it cool slowly) on my next brew because of yeast issues.

On the keg noted no DMS in his final beers that were cooled this way. I believe the analysis of the Australian method of cooling in a large plastic containers was similar IIRC.

It must be the boiling off of the SMM that makes the difference.
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onthekeg

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Post Mon Jan 04, 2010 7:50 am

Re: How quickly does DMS build up?

I haven't had any issues with DMS in pilsners with the hot kegging method. I have made 3 batches, and there have been zero issues. There is only so much SMM in the grain bill, once it has converted to DMS and boiled off there isn't anymore being produced in my actual experience.
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Lynux

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Post Mon Jan 04, 2010 11:45 am

Re: How quickly does DMS build up?

OTK,

Did you boil your pilsner for 90min? I'm going to be brewing a pils using your no chill to keg method so i'm curious.

I've made 100% pilsner beers in the past with only a 60 min boil and didn't notice any DMS.
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