So I am well aware of the conventional wisdom that you "never" boil your wort with the lid covering your kettle. The theory is that it will trap the precursors to DMS in your wort. Commercial breweries boil with a covered kettle except for the exhaust flue. It seems like most of these exhaust flues are pretty small in relation to the quantity of wort being boiled. Obviously commercial systems have been engineered and have taken the potential DMS issue into consideration. So would I be right in also assuming that if I left the lid on my kettle "ajar" that would be enough to negate any potential risk of DMS....or am I missing something?
Boiling with lid on question.....
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hannibalmdq
Well-Known Member
You're not missing anything. I boil mostly covered and have never tasted the flavors attributed to DMS in my beer. I get about a 15-25 percent boil off depending on boil length and environmental conditions. From what I can read here and there that seems in the accepted range. There are plenty of people that boil partially or mostly covered that claim similar results.
Be aware that some have very high sensitives to DMS and some people don't. There are also a lot of people who will tell you that you'll produce a poor product if you boil even remotely covered. You can find out for yourself and it'll only cost you a batch.
I've never tried it! I've heard about DSM a lot ! Do what you need to do to get a boil. All I've heard is you might get a corn taste in your beer. They say it can happen to anybody, also during fermentation.
The real question we need to ask is, "what are the properties of DMS precursors?". Without knowing something about their properties (vaporization temperatures, etc.) We can't say definitively how they might behave.
In light of this, the other question is, "is there a reason you want to risk it"? And then of course, "what's the reason?". We might be able to get around the issue by problem solving what is preventing you from boiling without the lid on.
In light of this, the other question is, "is there a reason you want to risk it"? And then of course, "what's the reason?". We might be able to get around the issue by problem solving what is preventing you from boiling without the lid on.
hannibalmdq
Well-Known Member
I don't think he's asking about risking it by boiling completely covered. I think he's mostly getting at, how much venting does one really need to drive off DMS precursors?
The big boys don't boil in giant uncovered kettles, probably because it would take a truly massive burner to keep a boil on the volumes of wort they run and it would require a ton more fuel which would drive up costs for them. They boil mostly covered with giant flues to carry off the vapor.
Conventional wisdom is that boil completely uncovered is best. However, there are plenty of people, including large brewers that don't come anywhere close to doing that.
He might be concerned with boiling off too much liquid resulting in less beer per batch.
When i spend hours brewing and get 4 gallons instead of 5 it kinda pisses me off, perhaps the OP feels the same way.
When i spend hours brewing and get 4 gallons instead of 5 it kinda pisses me off, perhaps the OP feels the same way.
hannibalmdq
Well-Known Member
Well, you could always top back up with water assuming you hit your pre-boil volume and gravity. If you overshot your boil you'd be over to your target OG and topping back up would give you the volume you wanted at the gravity you wanted.
You're hops might be a little off but your utilization would be slightly higher in the presence of more concentrated sugar solution....so it probably wouldn't be that off.
That is exactly what I am talking about! How much venting do you need to drive off DMS precursors? I brew in a pretty temperate climate (SoCal) so I wouldn't expect to waste that much fuel but I am sure it would make a difference in both time/money. I recently toured a small 7bbl brewery that had a direct fire kettle which got me thinking about this. Their exhaust flue was probably 6-8 inches in diameter....other wise the kettle was completely sealed except for a port to add hops. If you look at other brewing systems this type of setup is completely normal and been vetted by decades/centuries of brewing experience. Why does a boil kettle that is mostly covered work for commercial breweries yet we, myself included, discourage boiling with a lid on....even partially?
I don't think it's the venting that is the major problem, it's the cool lid where the DMS precursors can condense and then drip back into your beer. If the lid is hot, you shouldn't get condensation and all the DMS precursors will be carried off by the steam escaping. Are you willing to chance a batch in the spirit of experimentation? Put the lid on leaving a small area to vent the steam uncovered, then put something insulating on the lid to keep it from condensing the steam. I'd probably used a folded towel as the insulator as I always have them handy anyway.
+1^ to what RM-MN said.
As to the red highlighted quote above, that is not a simple exhaust flue commercial breweries use. It's a heavily power-vented hood, and if you've ever been in a brewery, on the brewing deck, you can actually see air and vapor being sucked in at a ridiculous speed wherever there's an opening, like the inspection hatch. The characteristic shape was designed for the purpose of maximizing air speed and reducing condensation as much as possible, not just looking pretty.
From what I've read as long as steam can escape it will take DMS precursors (SMM) with it, so a partially covered kettle could work just fine. The refluxing, through condensation forming on the bottom side of the lid, dripping back into the boiling wort, could be a potential SMM retaining problem. Hence keeping refluxing to a minimum by insulating, or other methods may remedy that effectively. Not sure when this can become a problem.
The perceived flavor threshold for DMS is very low- 10-150 parts per billion!
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hannibalmdq
Well-Known Member
Please don't misunderstand. I'm not claiming that DMS doesn't exist. Just that sensitivities vary greatly from person to person. Those numbers are low but also cover a range of 1500%. Also, some people may not notice it because they don't find it as objectional as others.
There is a non zero portion of this board alone that claims they can't taste it, even in commercial examples of beers that supposedly have a ton of DMS.
I'm don't care for acetalhyde, I think. Whatever that appley taste is. Can't stand it.
Just because I can't taste DMS in my beer and my friends can't either doesn't mean that my beer isn't riddled with the stuff. However, at the moment, I don't have a reason to believe that's the case.
We do know these properties. The precursor to DMS (SMM) is not what is boiled off. The heat of the boil breaks the SMM down to DMS. Then the continued boiling will volatilize the DMS (its boiling point is 99F) and the DMS will evaporate off with the steam. This BeerSmith article explains it pretty well and gives half life rates for DMS. I also found this paper (it's pretty dated, but I believe the science still holds up) which is pretty interesting and has a nice graphic flow chart of DMS (Figure 5).
+1 to this. The opening for the vent may be pretty small but I guarantee they all have a big exhaust fan in them to pull off most of the steam.
Thanks for the explanantion.....makes perfect sense!
hannibalmdq
Well-Known Member
I think I may just do a test. 100 pils malt mash, split into 2 boils. Do one with the lid completely off and one with the lid left on. Same yeast, hops, and fermentation schedule. I'm very curious.
If you have the means, do a 3 way split, one with lid off, one with lid on, and one with lid on but insulated. Supposedly the DMS condenses on the lid and drips back in causing the flavor. Insulated lid may eliminate that.:rockin:
hannibalmdq
Well-Known Member
I think I'm going to buy the stuff for this test today.
100% pils malt. I'll use WLP029 for a clean fermentation to let any potential DMS come through. Any thoughts on hops? I have the following on hand
Magnum
Willamette
Cascade
Chinook
Columbus
Centennial
Hallertau
Nelson (an open packet that's a little old)
100% pils malt. I'll use WLP029 for a clean fermentation to let any potential DMS come through. Any thoughts on hops? I have the following on hand
Magnum
Willamette
Cascade
Chinook
Columbus
Centennial
Hallertau
Nelson (an open packet that's a little old)
wobdee
Junior Member
Interesting test. I think I'd brew a Helles type beer, something that's not too hoppy that could hide any off flavors. Maybe bitter with a little Magnum and a small late addition of Hallertau for balance.
hannibalmdq
Well-Known Member
So I picked up 4.25 lbs of Pilsner malt.
Thinking through the process a little more, I think my normal split batch process is okay, except that with the lid on, my boil off rate for the "DMS" batch is going to be significantly lower leading to a lower original gravity compared to the "normal" batch.
Does anyone have any thoughts on how to address this? Since the batch sizes will be small, the differences in original gravity could be quite large if I don't address it at all.
Maybe I could try to dilute the "normal" batch pre-boil so that I hit a post-boil gravity closer to what the "DMS" batch will be.
Thinking through the process a little more, I think my normal split batch process is okay, except that with the lid on, my boil off rate for the "DMS" batch is going to be significantly lower leading to a lower original gravity compared to the "normal" batch.
Does anyone have any thoughts on how to address this? Since the batch sizes will be small, the differences in original gravity could be quite large if I don't address it at all.
Maybe I could try to dilute the "normal" batch pre-boil so that I hit a post-boil gravity closer to what the "DMS" batch will be.
Here's the cover that UC Davis uses on their induction system:
When you report back after the test, can you include the boil temp and the vigor of the boil.
EJay
Well-Known Member
Boil temp will be the same, won't it (assuming same altitude and pressure).
Kind of....about 212f but, as you said, altitude/pressure/humidity causes the temp at boil to be higher or lower. I assume you'll reach boiling point sooner (possibly at slighly lower temp) with lid on vs. lid off.
This is from the BeerSmith article, and is a factor I didn't know:
"Rapidly cooling your wort after boiling is also important. The SMM to DMS conversion continues at temperatures well below boiling, so DMS is produced even while the wort is cooling after the boil. However, unlike the mash, DMS produced while cooling cannot be boiled off. This conversion continues even if the hot wort is vented. For every hour you have hot wort sitting around, you will produce approximately a 30% increase in DMS."
I wonder if force oxygenation with bottled o2 would drive off some of the cooling DMS with the bubbles from the o2 stone?
hannibalmdq
Well-Known Member
There are a whole host of brewers in Australia who take issue with the slow chilling causes DMS flavors.
I agree and I have used the no chill method before. However, I'm fuzzy on my understanding. According to the article re: DMS half life, a 90 minute boil will drive off 79% of the DMS. However as it cools, DMS is still converting at the at of 30% per hour. Is that 30% of the available 31% that was not driven off by the boil (i.e. 100 possible DMS - 79% driven off by boil leave 31% potential DMS remaining). If so, the no chill following a 90 minute boil would produce a maximum of 31% of the possible amount of DMS. I don't know if it works that way. ALSO, sorry to be headed a little
, I am very interested in the experiment discussed below.hannibalmdq
Well-Known Member
Well, brew day is complete.
100% Pilsner Malt, mashed for about 2 hours at 151, drained 3.3 gallons of 1.036 wort.
1.25 gallons went in a kettle to be the DMS batch. I added 3.5 oz of Extra Light DME to try to mimic the gravity increase from the boiloff that isn't going to happen. It started at 1.044 and finished at 1.046. A 30 IBU charge of Magnum was added at 60 minutes. It's cooling covered on the counter.
2.05 gallons went another kettle to be the normal batch. After a 90 minute boil, a 30 IBU charge of Magnum at 60 minustes, and a 15 minute cool to 80 degrees in an ice bath, it finished at 1.050. It's sitting in a 1 gallon carboy chilling further in the fridge.
1.046 to 1.050. I'm gonna call it close enough. I'll put the DMS batch in another 1 gallon carboy tonight (provided its cool enough then) and pop them both in the fermentation chamber and set the regulator for 58.
In the morning, I'll pitch equal amounts of fresh WLP028 (Edinburgh Ale) slurry from a batch I bottled last night using MR Malty to guide my pitch amounts. I'll ferment at 60 and see where this goes.
100% Pilsner Malt, mashed for about 2 hours at 151, drained 3.3 gallons of 1.036 wort.
1.25 gallons went in a kettle to be the DMS batch. I added 3.5 oz of Extra Light DME to try to mimic the gravity increase from the boiloff that isn't going to happen. It started at 1.044 and finished at 1.046. A 30 IBU charge of Magnum was added at 60 minutes. It's cooling covered on the counter.
2.05 gallons went another kettle to be the normal batch. After a 90 minute boil, a 30 IBU charge of Magnum at 60 minustes, and a 15 minute cool to 80 degrees in an ice bath, it finished at 1.050. It's sitting in a 1 gallon carboy chilling further in the fridge.
1.046 to 1.050. I'm gonna call it close enough. I'll put the DMS batch in another 1 gallon carboy tonight (provided its cool enough then) and pop them both in the fermentation chamber and set the regulator for 58.
In the morning, I'll pitch equal amounts of fresh WLP028 (Edinburgh Ale) slurry from a batch I bottled last night using MR Malty to guide my pitch amounts. I'll ferment at 60 and see where this goes.
hannibalmdq
Well-Known Member
So the ferment went pretty quick which I expected. OG was modest and the yeast was pitched from a fresh cake using Mr Malty as a guide. I erred on the side of caution with my pitch rates . The DMS batch is sitting at 1.011 (76 % attenuation from 1.046). The control batch is sitting at 1.013 (74% attenuation from 1.050). I'm letting them come up to ambient (70ish) and they'll sit for another week at least. WLP028 is a slow floc so maybe they'll shave off another couple points off as the beer clears.
I couldn't really pick out any difference in appearance or aroma but my nose isn't particularly great and any DMS might take a while to show up given how it's produced.
I couldn't really pick out any difference in appearance or aroma but my nose isn't particularly great and any DMS might take a while to show up given how it's produced.
hannibalmdq
Well-Known Member
The beer cleared up over the last 8 days so I went ahead an packaged it. Pardon the poor photo. It's actually quite a bit cleared that the grainy pic shows. The DMS batch is marginally darker. Not as dark as the photo. but it's noticeable. I figure it's the dry malt extract I added.
The gravity didn't change since my last post. The DMS batch finished at 1.011 (76 % attenuation from 1.046). The control batch is finished at 1.013 (74% attenuation from 1.050).
The both smell like sweet pilsner malt with no real notable hop aroma (which isn't surprising). The control tastes alright, kinda bland, but hey, that was the point. The DMS is certainly different. It's still crisp and sweet but there is a slight vegetably thing going on. I think I may have made DMS! I'm really hoping that it becomes more prominent after it carbs up.
The gravity didn't change since my last post. The DMS batch finished at 1.011 (76 % attenuation from 1.046). The control batch is finished at 1.013 (74% attenuation from 1.050).
The both smell like sweet pilsner malt with no real notable hop aroma (which isn't surprising). The control tastes alright, kinda bland, but hey, that was the point. The DMS is certainly different. It's still crisp and sweet but there is a slight vegetably thing going on. I think I may have made DMS! I'm really hoping that it becomes more prominent after it carbs up.
Great experiment. Report back on your findings.
processhead
Well-Known Member
Brewed today and covered the kettle through part of the boil.
It had me thinking about the effects, so I will be following this thread and noting the results in my batch vs others.
It had me thinking about the effects, so I will be following this thread and noting the results in my batch vs others.
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