90 minute boils

Hey Folks: I have started doing 90 minute boils because I have been using Pilsner malt in a few recipes. I know Pilsner needs a 90 min. boil but do any other malts require this? Vienna? Munich?
I also know(think) that a 90 min. boil makes for a cleaner beer. It can also darken beer. Any other attributes for or against a 90 boil. Personally I like the 60 min because it makes for a shorter brew day. My brew days have grown in time recently due to double decoc brewing and 90 minute boils. Not complaining, just wondering. Thanks

Good question, I'm in the need to know too. I've had a few belgian strong ales that had 90 min boils as well, but not seen that on many recipes. What is the reason for vs against? I'm not as worried about the extra half hour, and if it can't hurt, I'd rather just do the 90 min boil instead.... comments, suggestions?

They just addressed this on the last episode of Brew Strong and according to the show's hosts the reason you do a 90 minute boil for pilsners is to drive off DMS (dimethyl sulfide) which can be prevalent in lighter malts. DMS is an an aroma similar to corn that forms at high temperatures, but can be driven off by a long rolling boil. Covering the boil would defeat this as the steam would precipitate on the pot lid and drip back into the boil. The rule of thumb that they expressed on the show was that generally the lighter the malt you have the longer the boil you should do.

They also mentioned that DMS is also formed while the beer is cooling after the boil which is one of the reason you should cool your wort down quickly after the boil.

I boil all of my pale beers for 90 minutes for improved wort clarity. No chill haze here. :cross:

A 90 minute boil means you need a slighter large sparge volume which equates to higher efficiency using either batch or fly sparging. This efficiency comes at the price of extra propane or electricity (for those lucky enough to have electric heating elements) so TANSTAAFL.

Listen to the Brew Strong episode on DMS. It pretty much covers why you need to boil for 90 min with pilsner malt. Just ignore the first 15 minutes where Jamil talks about ****ing sheep.

take the below with a grain of salt. it's something i heard, not something i believe.

my lhbs owner insists that 90 minute boils aren't necessary with ANY modern malts. he says that dms is only a problem with undermodified malt and that these days pretty much anything you buy in a hbs is well modified.

he's the only one i've heard say this though, has anybody else heard similar? i often do 90 minute boils just for efficiency's sake, and rarely use pilsner malt anyway, but i'm curious.

EDIT: sorry if this is covered in the brew strong podcast, i can't listen to it here at work. i'll try to give it a listen tonight.

The biggest reason for a 90 min boil is DMS. DMS (dimethyl sulfide) is volatile and perceived at a very low level in beer. Malts contain precursors to DMS. These precursors get broken down by heat into DMS. Since you have to boil wort, you are forced to make DMS.

The reason pilsner malt is subject to longer boil is that it is very lightly kilned. Even US 2 row is kilned enough that more of the precursor is driven out. English pale ale malt is kilned even more. Munich and Vienna so much so that DMS is virtually not a problem.

DMS has a half life of approximately 30 min at 212*F. That means that after 30 min of boiling, half of the DMS will be driven off. Boil for 30 more min and half of the remaining DMS is driven off...and so on. Most studies show that after 100 minutes, all DMS is eliminated. Since SOME DMS is desirable in beer, we usually stop at 90 min.

Chilling wort is also important to stop DMS production. The precursors are broken down into DMS starting at around 140*F. When you start to cool the wort, DMS is still being produced until it reaches this threshold. Since the wort is no longer boiling, no DMS is driven off. Therefore, it is important to cool lighter beer with a lot of pilsner malt as fast as possible.

As for the modified malt, I've never heard that. A protein rest is pretty useless if you aren't using unmalted grain. No matter how modified the grain is, it will still contain DMS precursors. The lighter the malt (ie pilsner), the more it has.

A longer boil may precipitate more proteins which while increasing clarity might also reduce head retention. I've been doing some German lagers and Belgian ales so I've been using Pils malt as a base almost exclusively lately. I have been doing 100 min. boils. But all these beers take so long to be ready that I haven't tasted any of them.

Over the past year, I completely lapsed on the 90 minute pilsner boil rule with a few beers and brewed with my standard 60 minute boil (starting after the break so it's a wee bit longer than 60 in reality). No one that had sampled the beers commented on DMS and I could not detect any DMS in these batches.

Looking at most of the info online, I saw three commonly cited factors for DMS off-flavors: SMM content of the malt, boil intensity/length and post-boil chilling practice. I do a fairly hard boil and chill my batches quickly after flame-out...that combined with the level of SMM in my pils malt must have been enough to keep these batches in the clear w/ just a 60 minute boil. Personally, I'll prb stick with a longer boil on delicate pils beers but I'm not so certain of the absolute necessity in all cases.

Edcculus said:

Listen to the Brew Strong episode on DMS. It pretty much covers why you need to boil for 90 min with pilsner malt. Just ignore the first 15 minutes where Jamil talks about ****ing sheep.

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I really thought you were joking about 15 minutes talking about sheep ****ing. Oh no, you were serious.

Edcculus said:

DMS has a half life of approximately 30 min at 212*F. That means that after 30 min of boiling, half of the DMS will be driven off. Boil for 30 more min and half of the remaining DMS is driven off...and so on. Most studies show that after 100 minutes, all DMS is eliminated. Since SOME DMS is desirable in beer, we usually stop at 90 min.

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If half is gone after 30min and the other half after 60 min, wouldn't all the dma be gone? I actually boil all my beers 70 to 75 minutes, I wait approx 10 minutes after hot break before the first hop addition.

If half is gone after 30min and the other half after 60 min, wouldn't all the dma be gone?

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No, 3/4 would be gone and 1/4 would be remaining.

Boil for 30 more min and half of the remaining DMS is driven off...and so on.

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brewt00l said:

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I do a fairly hard boil and chill my batches quickly after flame-out...that combined with the level of SMM in my pils malt must have been enough to keep these batches in the clear w/ just a 60 minute boil. Personally, I'll prb stick with a longer boil on delicate pils beers but I'm not so certain of the absolute necessity in all cases.

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Jamil actually says he does 60 minute boils now for that reason. He boils hard and uses the whirlpool chiller. Since he can chill below 140 in 1 minute, he doesn't need a 90 min boil.

I've done 90 minute boils on my past 3 brews, and all of them have resulted in clear beers (before, I had a lot of issues with chill haze.) YMMV!

Edcculus said:

Jamil actually says he does 60 minute boils now for that reason. He boils hard and uses the whirlpool chiller. Since he can chill below 140 in 1 minute, he doesn't need a 90 min boil.

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Interesting..I'm gonna have to hit that podcast up when I get home tonight.