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DMS boiloff - Rolling boil and lid tradeoff

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BolgBeorach

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Hey everybody. Yesterday I brewed Revvy's Leffe clone. Despite a few hiccups (still a newbie), it went mostly OK. One of the things that has been worrying me has been the boil, however. My set up is pretty basic, and I use a hotplate to get the wort boiling. As a result, I keep a lid on the pot to get a rolling boil, because it basically just simmers otherwise, and doesn't get that nice, satisfying round boil that is needed. The lid I'm using is a glass, shallow bell-shaped sort of thing, and so I can see that the steam seems to convey itself down the curve of the lid and out under it, meaning that it is still escaping. My question is how much this will affect the boil-off of DMS precursor. Is it better that I got the boil rolling for most of the 90 mins with the lid, or would it have been better to just have had it simmering away in an open pot? It's only today, on doing more detailed reading on the topic that I realise I should have thought about this a bit more yesterday. I haven't encountered the DMS flavour in the other beers I've done, but this is also the first time I have used pilsner malt grain, so I don't know how much of a bearing that has on the issue.
 

Dland

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I would say you'd be better off with lid off. The DMS only leaves if steam escapes. That said, you kind of need a "vigorous boil" too, according to the experts. Maybe you won't taste or mind the DMS too much. I'd look into getting a higher amp hot plate in future.

I brew with pils all the time, use a 60 min hearty boil w lid off, and rapid cooling of wort to 160F after boil, and don't get any DMS, that I can detect anyway.
 
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BolgBeorach

BolgBeorach

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I would say you'd be better off with lid off. The DMS only leaves if steam escapes. That said, you kind of need a "vigorous boil" too, according to the experts. Maybe you won't taste or mind the DMS too much. I'd look into getting a higher amp hot plate in future.

I brew with pils all the time, use a 60 min hearty boil w lid off, and rapid cooling of wort to 160F after boil, and don't get any DMS, that I can detect anyway.
The steam was still escaping under the lid. The convex shape of the lid allowed the steam to roll under the top and out through a narrow gap between the lip of the pot and the lid. It just might not have been escaping at the rate it should have, and condensing to a degree on the lid. I did have the lid off for a certain amount of time, but not for the majority of the boil, and it was not boiling vigorously when that was the case. I would like to get a better heat source (and pot, for that matter) but I am unfortunately limited in both resources and places to brew at the moment, so the hot plate that I have must suffice haha.
 

Dland

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Your beer will probably be fine, sounds like you are doing what you can w what you have. Maybe keep an eye out at second hand shop for gear upgrades.
 
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BolgBeorach

BolgBeorach

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Your beer will probably be fine, sounds like you are doing what you can w what you have. Maybe keep an eye out at second hand shop for gear upgrades.
Thanks man. Here's hoping!
 

VikeMan

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My question is how much this will affect the boil-off of DMS precursor. Is it better that I got the boil rolling for most of the 90 mins with the lid, or would it have been better to just have had it simmering away in an open pot?
It's hard to quantify this, but based on the description of your equipment, my hunch is that an open simmer would have been more effective at getting rid of the DMS than a rolling but mostly closed boil. The ability of the steam to escape is key.

BTW, it's not actually the precursor (SMM) that boils off. Heat thermally degrades SMM to DMS, which then gradually boils off, in a sort of "half life" fashion. i.e. depending on the boil, if you get rid of half the DMS in "X" minutes, another "X" minutes will get you down to about 25% of the original qty. The hope is to get it below the flavor threshold, about 25–50 μg/L depending on the taster. Complicating this a little is the fact that SMM is only one of two precursors from malt that can make DMS. The other is DMSO, which yeast can reduce to DMS during fermentation.
 
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BolgBeorach

BolgBeorach

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It's hard to quantify this, but based on the description of your equipment, my hunch is that an open simmer would have been more effective at getting rid of the DMS than a rolling but mostly closed boil. The ability of the steam to escape is key.

BTW, it's not actually the precursor (SMM) that boils off. Heat thermally degrades SMM to DMS, which then gradually boils off, in a sort of "half life" fashion. i.e. depending on the boil, if you get rid of half the DMS in "X" minutes, another "X" minutes will get you down to about 25% of the original qty. The hope is to get it below the flavor threshold, about 25–50 μg/L depending on the taster. Complicating this a little is the fact that SMM is only one of two precursors from malt that can make DMS. The other is DMSO, which yeast can reduce to DMS during fermentation.
Yeah, the steam did seem to be escaping at a decent rate, but it's hard to tell how much more than if it had been totally open. The difference between the boil I was getting lid on and lid off was night and day, which is why I had been leaving it on. I actually have no experience with DMS, but I didn't get any strong, strange scent from the wort post-boil. I'm just hoping I won't get a surprise when I take a reading in a few weeks :/

I’m guessing that your brewing all grain not extract?
It was indeed an all-grain brew.
 

BucksIPA

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It takes about 35-40 minuts for the boil temp to break down smm to dms in the brew kettle Once it converts, its a fiarly low temp that will drive dms to a gas. Knowing this information can allow you to formulate a process.

From this, you can most likely lid the kettle to about 40 minutes or so. Its really a temperature that converts, then a boil will drive off the dms. Water can only get so hot and the solability of that dms is most likely roughly the same at a simmer as a rough boil. Theres more mixing in a rough boil, but at a temp and solubility, it will escape. Here you would want to allow gases to escape freely. Technically could condense on the lid.

Im not in favor of the rough boil, especially with an open flame as you can create off flavors with pilsner malt. If your going for like a pilsner urquell, this may be beneficial. Something like a german or danish pilsner, probably not. The whole point of a pilsner (in the non czech means) is to produce a very delicate beer, it the reason why it is considered the pinnacle in brewing, as it is not the easiest thing to do with all of the challenges they face. A homebrew or small craft brewery method is to take a simple process approach, and thats why there are not many good examples of pilsners from those fields.
 
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BolgBeorach

BolgBeorach

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It takes about 35-40 minuts for the boil temp to break down smm to dms in the brew kettle Once it converts, its a fiarly low temp that will drive dms to a gas. Knowing this information can allow you to formulate a process.

From this, you can most likely lid the kettle to about 40 minutes or so. Its really a temperature that converts, then a boil will drive off the dms. Water can only get so hot and the solability of that dms is most likely roughly the same at a simmer as a rough boil. Theres more mixing in a rough boil, but at a temp and solubility, it will escape. Here you would want to allow gases to escape freely. Technically could condense on the lid.

Im not in favor of the rough boil, especially with an open flame as you can create off flavors with pilsner malt. If your going for like a pilsner urquell, this may be beneficial. Something like a german or danish pilsner, probably not. The whole point of a pilsner (in the non czech means) is to produce a very delicate beer, it the reason why it is considered the pinnacle in brewing, as it is not the easiest thing to do with all of the challenges they face. A homebrew or small craft brewery method is to take a simple process approach, and thats why there are not many good examples of pilsners from those fields.
Thanks for the info. So I actually did have the lid off for a time - maybe for about 15-20 minutes after my 30 minute hop additions. Would that have been enough time to blow out the DMS that had been already heated into a gas while the lid was on?
 

DVCNick

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To determine actual differences here, you're probably going to need lab grade analysis; that is my guess.

I keep the boil relatively low, and the lid partly on, for two reasons. 1) A bigger boil isn't really getting the liquid any hotter, you are just using more fuel and losing volume to boil off evaporation faster. 2) I'm in the garage and hopefully the lid is minimizing the chances of whatever might be floating in the air getting into the beer.
I've never experienced a flavor similar to the description for DMS... ymmv.
 

VikeMan

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A bigger boil isn't really getting the liquid any hotter, you are just using more fuel and losing volume to boil off evaporation faster.
Heat converts SMM to DMS. It's true that the wort for the most part won't be any hotter between a simmer and a boil. But conversion is only half the story. A more vigorous boil, and/or a longer boil, and/or more surface area causes more of the converted DMS to vaporize.
 

Brooothru

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Heat converts SMM to DMS. It's true that the wort for the most part won't be any hotter between a simmer and a boil. But conversion is only half the story. A more vigorous boil, and/or a longer boil, and/or more surface area causes more of the converted DMS to vaporize.
That raises some interesting points and a few questions as well. I try to practice LoDO procedures, so a low boil is my normal. As soon as I get full boil/hot break I skim the scum and let the wort settle into a simmering boil. The steam is free to escape, but I wonder if it would encourage the DMS to vaporize quicker if I waited to remove the foam (greater surface area).

Would the increasing heat in the wort before boil is reached be enough to convert SMM to DMS? If so, my thinking is that having the foam left in the pot for the first 20-30 minutes of a 75 minute boil might drive off more hot side DMS. Your thoughts?

Brooo Brother
 

VikeMan

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As soon as I get full boil/hot break I skim the scum and let the wort settle into a simmering boil. The steam is free to escape, but I wonder if it would encourage the DMS to vaporize quicker if I waited to remove the foam (greater surface area).
Foam has been shown to enhance DMS vaporization. But when you say scum, that sounds like coagulated proteins, etc., which in that form I would bet hinders DMS vaporization.

Would the increasing heat in the wort before boil is reached be enough to convert SMM to DMS? If so, my thinking is that having the foam left in the pot for the first 20-30 minutes of a 75 minute boil might drive off more hot side DMS. Your thoughts?
I'm not sure how you would increase heat before boil is reached without causing the boil to start sooner...do you mean heat for longer but keep the wort from actually coming to a boil? SMM does convert to DMS at temps below boiling. It can happen in a whirlpool/hopstand, for example.
 

Brooothru

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Foam has been shown to enhance DMS vaporization. But when you say scum, that sounds like coagulated proteins, etc., which in that form I would bet hinders DMS vaporization.



I'm not sure how you would increase heat before boil is reached without causing the boil to start sooner...do you mean heat for longer but keep the wort from actually coming to a boil? SMM does convert to DMS at temps below boiling. It can happen in a whirlpool/hopstand, for example.
Yeah, I wasn't very clear about the heating. I meant to say "while it's heating up" before it starts to boil. And you're right about the coagulation proteins being the 'scum'. That's what I try to skim off as soon as it forms to avoid boilovers. I usually don't have alot of foam with a gentle boil.

So I guess my question is what the range of temperature where SMM to DMS conversion occurs. I like to do a :20 min. hop stand at 82°C/180°F with a quick cool down from boil, stand :20, chill to 16°C/61°F for a kettle whirlpool before transferring to the fermenter. So am I risking more DMS production between 82C-16C?

Also, what yeasts/temperatures should be avoided to reduce DMS production during fermentation?

Brooo Brother
 

VikeMan

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So I guess my question is what the range of temperature where SMM to DMS conversion occurs. I like to do a :20 min. hop stand at 82°C/180°F with a quick cool down from boil, stand :20, chill to 16°C/61°F for a kettle whirlpool before transferring to the fermenter. So am I risking more DMS production between 82C-16C?
I believe SMM converts to DMS at temps above about 70C (158F). Hotter is faster.

Also, what yeasts/temperatures should be avoided to reduce DMS production during fermentation?
I'm not too familiar with the variables that affect the DMSO -> DMS path (via yeast DMSO reductase), but here's one paper for further reading:
 
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