Seems like such a newbie question, and I’ve done it both ways without ever really noticing a difference. But, recently I read there’s a risk of DMS by boiling with the lid on the kettle. I can’t imagine that this is really true, but what is the proper kettle lid etiquette? Open, covered, or partly covered, or none of the above and stop reading stuff?
It all depends of what you’re after. Partially or fully covering for a good amount of the boil helps to limit the heat input required to get to and maintain the boil and thereby reduces any extra thermal stress on the wort.
Uncovering for the last portion of the boil is enough to volatize and expel any DMS. A nice middle ground is to modify your lid with a “hatch” door of sorts, either on a swivel or hinge whereby you can open it to add hops and to allow for volatile compounds to escape.
I’m with Big Monk - partial lid with low stress boil for my pale beers, uncovering for the last 10 minutes of the boil. Also leaving the lid off for quick chilling, because it was claimed that covering during chilling allows for reformation of DMS.
Pils malt is the biggest producer of DMS, among the base malts, so that is when I have the heightened concern with covering the boil kettle.
During the early and mid stages of the boil, your kettle can be totally covered and you can turn down the heat to the point that the wort is only modestly circulating. However, you do need to uncover the kettle at least partially in the late stage of the boil to vent DMS. You must turn up the heat when you uncover since more heat is lost through evaporation. In addition, it is important that the wort has good circulation in the kettle to give the DMS the opportunity to escape at the wort surface.
Of course, if you are used to boiling off a gallon or two during a boil for a 5-gal batch, you’ll need to refigure your starting kettle volume to account for the smaller evaporation loss. We homebrewers boil FAR too hard and long. That actually damages the wort and creates beer that stales earlier. Getting your total evaporation loss to around 8% is a good goal. Pro’s target that evaporation percentage or less.
Evaporation rate is something I’ve been aware of and trying (with limited success) to improve. But what duration of boil do you think is desirable? I go 60 minutes, but I’ve seen some people advocating extremely short boils. (Protein coagulation aside, in most homebrew systems a certain length of time is needed for hop extraction, even when using FWH, it seems. Conflicting goals, or more out-of-the-box thinking required.)
EDIT Or does time matter if vigor of boil is reduced? Are we just talking total thermal stress, as the area under the time/temp curve if it were graphed? Or should time still be reduced?
I note that Kunze in his textbook now states that virtually all German breweries now limit their boil to 60 min. 90min boils are rare and are damaging.
When you are at an elevation of less than 1000 ft, you can generally count on almost all SMM to be converted to DMS in about a half hour. That leaves almost a half hour to expel that DMS with a modestly rolling boil. The first 30 minutes of the boil can be considered the SMM to DMS conversion stage and can be conducted with the kettle fully covered and at barely a boil.
If you have little or no pils malt in your grist, there is not much SMM in your wort. You might be able to shorten up the boil then. Short boils are possible if your grist was composed of slightly darker base malt (say 4L or higher), but remember that 60 min is a good compromise since that’s where hop isomerization rate flattens out. But if reducing heat stress and color pickup in your wort is important, then it is possible to reduce boil times a bit in some cases.
Thanks, Martin! Tomorrow’s 100% Pils. I’ll try sticking with 60, but covered and gently boiling the first 30 and a little gentler than usual thereafter. That just might get me down near 8% (from current 11%) without having to rethink anything else. (My elevation is 1004 ft – close enough!) [Awaiting delivery of my own Kunze, should have bitten the bullet on the price long ago.]
Heh…
You should have reached out to me, I get special pricing on Kunze, Narziss, Fix, etc.
Ph also matters a pH of 5.4 splits dms twice as fast.
Well, I’ll keep you in mind! I ordered from Siebel, more expensive than the publisher, but w/o international shipping. (Where I got the bargain priced DeClerck, which starts to seem as dated as Thausing!)
Bru’n Water predicts pH 5.40, but actual was a bit lower last time with this profile. This time I’ll be super careful with my acid addition and see if that fixes it.
Good to know, Bryan. Thanks for that tidbit. I pull the lid at 16’ for BTB and leave it off, then 14’ Whirlfloc (and immersion chiller into the boil with a little more heat added) and 10’ yeast nutrient addition; typically a 0’ hop add and right to recirc chilling. I try to achieve a stress-reduced boil while still boiling at the late stage vigorously enough to drive off the potential for DMS issues.
Pils worts should be mashed at 5.4 pH and boiled at 5.4 for most of the duration. If the brewer wants the boiled wort to be at a lower pH, it is OK to add the additional lactic acid at the end of the boil. As Bryan mentioned, SMM conversion to DMS proceeds at a higher rate when the pH is elevated a bit.
What is the reason for reducing pH later in the boil?
My pH seems to lock in and hold steady right through the mash and boil (only drops by ~0.1 in the boil) and I just leave it alone. Others acidify in the kettle. Why? (I have a feeling this is in DeClerck but I can’t remember.) I see a normal pH drop in fermentation.
Better cold break, lessens lag time, etc.
Haven’t had difficulty in those areas. But thanks for the quick response, I’ll take it into consideration if I do see a need to address chilled wort issues.
I have first editions of “A Textbook of Brewing”. They may be dated in some places but you’ll be amazed how much is still relevant after 70+ years. Amazing books.
Yes indeed, relevant and helpful enough that I’ve leaned on it and resisted shelling out for the Kunze until now. But thanks to you guys on the forum it’s become obvious I need to fill out my bookshelf!
(BTW you’ve probably noted that there are still useful nuggets in Thausing after 100+ years. Shows how enormous a chunk of brewing science was done in the 19th c., with technology being the bulk of later advances!)
Brew’s in the settling tank, time to report. 60 min boil. 1st 40, lid just barely cracked open to prevent boil-over, heat ~70% of usual full-bore, wort very gently circulating. Last 20 lid off, heat on full.
Evaporation rate: 8% on the nose!
Moreover, the malt flavor of the wort is noticeably more rich and biscuity than usual.
A study maybe 20 years ago found that as long as you had 15% open space, you were good.
Good as to what?
DMS