Why is the boil "1 hour"?

[olie]

This is 1 of 2 n00b questions about boiling beer, the other one being about boiling-up some hops alpha-acid "extract" separately from the wort [LINK].

This question is about the wort-boil, though. Specifically, what's so magical about "1 hr"? Why can't we boil our beer for, say, 15 minutes?

NOTE: I know about the boil-time to get hops acids, but why not use 4x as strong hops for 15 minutes (again, "for example") ?

Is there something special that happens to the wort, chemically, that takes some longer amount of time and "1 hr" just seemed to about cover it in almost all circumstances? To kill bacteria, you don't even have to bring the water all the way to boiling! (I mean, unless you're using river-water, or some such. But, if you start with clean drinking water, not-quite-boiling is pretty close to sterile!)

So what's the deal, there? Why 1 hr?

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Also, on the flip side, is there any harm in boiling, let's say, for 4 hrs? Does something break down and become "no good"? Or is it just a matter of "that's too long, and unnecessary"?

Also-also: I'm happy to do some experimental batches myself, I'm just asking to see if anyone has already blazed this trail and wants to save me some time (and possibly ruined beer). I don't need to reinvent every wheel...!


Thanks!

 

[GnenieGone]

The 1hr boil is more about sulfide. The mash/grains have sulfur compounds which are boiled off. The longer the boil the cleaner the beer. I've done 15min boils with mostly dme and haven't noticed an issue. They're entire threads and papers about sulfur in beer but your taste buds are the final straw.

As far as 4hr boils no, no issues but one woyld only do such a long boil for very high alcohol beers. 2hr is the most I've done because of completely missing my OG...no issues.

 

[shoengine]

Isomerization of alpha acids, as you alluded to in your post. Even with four times as many hops (not that anyone would ever do that) you won't drive off the flavors of the hops after 15 minutes which would limit your ability to utilize bittering and flavor hops.

There is also the so-called maillard reactions that occur during the boil.

Additionally, there is a lot of common knowledge and tradition in brewing that is utilized for no other reason that it is just "done". You'll find a lot of discussions aboiut those sorts of things on this forum.

 

[olie]

I'll go read-up on maillard reactions but, yeah, the main point of this thread (and the linked one about "hops extract") is to help me sort out which things are "just done" because "great-grandpa did it that way" (or similar) and which are done for "actual reasons".

Just tryin' to learn!

(I recently learned that the German beer-purity-law had to add yeast as an allowed ingredient because, not so long ago (18xx, I think), they didn't realize that was part of the recipe. That and the "cut both ends off the ham"-type things [LINK] are what I'm trying to sort out.)

 

[deadwolfbones]

If you want to know about things that are "just done" vs. actually effective, head over to www.brulosophy.com. Endless reading there.

 

[Seanto]

I believe you can't effectively "bitter" the beer in such a short time frame. Hops become more bitter the longer you boil them. With just a 15 min boil, i would imagine that you will get alot of hop flavor and aromatics, but not raw bitterness. But you can do variable times with your boil. Some folks do a 45 min boil...some over 60. Just depends on what you want in the end product.

 

[helibrewer]

Several things happen during the boil and they occur at different rates. We denature and coagulate proteins (break material), we sanitize, we reduce the volume to achieve our desired starting gravity, we isomerize alpha acids, we drive off undesired volatile compounds such as DMS (which has a half life of about 20 minutes, so a one hour boil drives off about 75% of it). All of these reactions take different amounts of time to be effective.

One hour manages to get the desired results without using excess energy (longer boil) with diminishing returns. High pilsner malt grists are generally boiled for 90 minutes due to the higher amount of SMM from lighter kilning, SMM is the DMS precursor.

There seems to be some evidence that very long boils can impart changes to the wort due to the high thermal load, the most obvious of which is darkening.

 

[whiskeyjack]

A reason not mentioned here is its been the thing to do for the last 30+ years for homebrewers. I admit there are tons of benifits to a 60 minute boil, but it doesn't have to be set in stone. There have been one constant to homebrewing, and that is change. One thing that's been big last 5 years or so is experimenting as already mentioned with brulosophy. Lagers at ale temps, grain to glass in 14 days vs 1-2-3 method, biab/no chill etc, hazy ipa. I've been doing 30 minute boils lately. One con I find is you don't get as concentrated of a wort, but adding a little extra grain covers it. You either spend more on fuel and time or grains to makeup.