Rolling boil - lid on or off?

[Pegasus]

Hi,
read this on the 'How to Brew' site (link to page). It says the lid should be off when boiling to allow 'unwanted' sulphur compounds to boil off.

Would you agree?

Ta

Paul

[Jim]

Yes. I always boil with the lid off.

[basswulf]

Definitely off. Firstly, there's the safety side - a covered brew is much more prone to boiling over (you can demonstrate this with a small pot of pasta rather than wasting precious wort!). However, the boiling stage serves both to extract flavours from the hops and also to reduce the total volume through evaporation. I imagine the former would still work but your wort would be no thicker than when you started and you might be disappoined with the end result.

Extra tip - run a dehumidifier or keep a window cracked open - 90 minutes of rolling boil puts a lot of water vapour in the air!

Wulf

[Padalac]

Apparently other than sterilising the wort, one of the main reasons you want a rolling boil is to evaporate off DMS from the solution that you do not want in there:

I got this quote from the following article (https://byo.com/grains/item/1650-wort-b ... ew-science) :

Volatalize aromas
Dimethyl sulphide (DMS) is an intensely aromatic compound present in most beers. When it’s present in amounts large enough for it to be tasted and smelled, it can be an important flavor characteristic or defect. At low levels it smells of corn or sweet corn. When it is more intense it can resemble over-stewed vegetables or even garlic. In some European lagers, it is an important part of the flavor profile; a large regional brewer in the United States (Rolling Rock) also features it.

DMS is formed from s-methyl-methionine (SMM), which in turn is produced from amino acids during malting. SMM is converted to DMS by heat and then the DMS is volatilized and whisked away with the steam during wort boiling. Some homebrewers who leave a lid on the kettle find that this compound is re-introduced when the steam condenses on the lid and drips back in. Unless the precursor is all removed, then more DMS can be formed during wort clarification and this DMS will survive to the final beer. This is a problem in commercial breweries using whirlpools. For this reason, homebrewers should attempt to cool their wort as quickly as possible after the boil is complete.

--------------------------------

so yea, if you boil with the lid on you are likely to get a sweetcorn/corn like flavour in the beer, and possibly some stewed vegetable flavours. for most beer styles, this is generally considered an unwanted flavour.

cheers

[boingy]

I boil with the lid on and have a sideways exhaust pipe for steam to escape. DMS boils off at a way lower temperature than water so as long as there is a healthy amount of steam coming out of the pipe the DMS is going with it. I take the lid off a minute or two before flameout and leave it off during cooling. If it's good enough for my local micro it's good enough for me.

[Wezzel]

I boil with it three-quarters on. It retains more heat but still lets the DMS escape.

[Pegasus]

Thanks All,
will turn the extract fan to a higher setting in future

[fisherman]

Lid off

[clarets7]

Has anyone experience of simmering versus a rolling boil? Just read this from 'The Art of Brewing...' by James Herbert:

'I will now give you an exposition of the Burton system ... their boiling of the worts for strong Ales being very little varied from my system; the length of time for boiling strong worts averages from one and a half to two hours simmering; they never boil their worts hard, their object for that being to preserve the aromatic properties in their Ales, which causes to a great extent that soft and agreeable flavour which is most predominant in the Burton Ales;'

It would certainly make the removal of the steam easier, and reduce my rather high evaporation rate.

[Wonkydonkey]

I boil with it three-quarters on. It retains more heat but still lets the DMS escape.

+1 on this, it keeps a bit of the heat in and allows a good boil.
I read one of barnneys post, where he's got a Thermo pot with the lid on, and a truck flexy pipe fitted to the lid ( the type they use to remove exhaust gases from a garage while being serviced )

But what ever way it's done, a boil over is apita, and your more likely to have a boil over with the lid on.

[Aleman]

With my large system (150L Boiler) I have no alternative but to boil with the lid on, as apart for a small (~15%) hinged area at the front of the boiler the rest of the 'lid' is welded to the kettle. As others have said as long as steam can escape (I have a 2" vent on the big kit) then it's going to take DMS and other volatiles with it The lid will get so hot that any DMS in any condensate that does form will be gassed of anyway to escape in the steam. The lids open for the last 10 minutes of the boil as well

My small kit I rest the Thermopot lid on the boiler but raised an inch or two at the front.

My Large kit is gas powered, and the thermopot kit electric, but both are controllable (The electric one has a Phase Angle Controller reducing the power to the element) so boil overs are not an issue

[robbarwell]

Lid on for me but it has a chimney..Lid off for the last few mins to get the chiller in.

[JimJiminy]

Really interested by the answers in this thread. A couple have suggested that, so long as the steam can escape, the DMS will too.

It seems that, any reasonable system is going to have SOME way for the steam to escape (otherwise you are brewing in a pressure cooker). So does that mean that worries about DMS are overblown? Anyone here actually had this off-flavour in their own beer from using a lid (rather than just reading about the risk)?

My current lid has a small maybe 2cm hole (designed to take an airlock grommet). Steam definitely escapes from it. Will this be big enough to avoid DMS accumulation?

I'd much prefer to brew lid on. My flat does not enjoy multiple litres of water being vaporised inside it, especially during the winter. And I can get a rolling boil with far fewer watts going in, with lid on. But I'm not sure I want to risk brewing a batch of cabbage-beer to find out.

[Jim]

Really interested by the answers in this thread. A couple have suggested that, so long as the steam can escape, the DMS will too.

It seems that, any reasonable system is going to have SOME way for the steam to escape (otherwise you are brewing in a pressure cooker). So does that mean that worries about DMS are overblown? Anyone here actually had this off-flavour in their own beer from using a lid (rather than just reading about the risk)?

My current lid has a small maybe 2cm hole (designed to take an airlock grommet). Steam definitely escapes from it. Will this be big enough to avoid DMS accumulation?

I'd much prefer to brew lid on. My flat does not enjoy multiple litres of water being vaporised inside it, especially during the winter. And I can get a rolling boil with far fewer watts going in, with lid on. But I'm not sure I want to risk brewing a batch of cabbage-beer to find out.

Your system for removing the steam needs to make sure that condensation doesn't drip back into the boiler (carrying back the DMS with it). I would say (based on my early experiences of boiling wort with the lid on for exactly the reasons you mentioned) that a small hole in the lid is NOT enough to allow the DMS to boil off.

[Kev888]

Hi, read this on the 'How to Brew' site (link to page). It says the lid should be off when boiling to allow 'unwanted' sulphur compounds to boil off.
Would you agree?

Not necessarily, I feel that it depends on the particular setup. In my case I boil with the lid 'mostly' on (or closed but with a chimney/vent), as it saves energy whilst permitting a much more convincing rolling boil than with the lid fully off. However if your boiler is over-powered and can't be throttled back then you may need the lid off to avoid boil-overs, though it will use/waste more energy.

Personally I suspected that the lid needing to be fully on for reasons of DMS 'may' have originated through well-meaning but mistaken logic (overlooking the temperature of the steam-heated lid and the volatility of DMS). At least, I've not seen any first-hand evidence that it actually happens in practice, quite the opposite in fact- I've 'never' had any problems with it, and almost all commercial breweries I've seen have boilers with just some sort of relatively small chimney or vent.

EDIT: though it must be said I'm no great scientific authority and it looks like Jim and some others may have had conflicting experiences, which is interesting (and which I'm not disbelieving). I wonder if one can go too far - perhaps if the heat needs to be 'so' low to avoid boil overs with a small vent, or if pressure builds up or something, then possibly the DMS conversion starts to suffer?

Cheers
Kev