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120 min boil

condog

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Other than hop utilization, what is the purpose of extended boil times listed in some recipes?
 
1.  Concentrate the wort to reach a desired post-boil gravity. 
2.  Reduce Di-Methyl Sulfide (DMS).

I made a Scottish 80/- last Sunday.  I tried fly sparging instead of batch sparging, just to see how it would go.  my extraction wasn't great, and I finally finished with a batch sparge to get some of the unextracted sugars out of the grain.  I got all the sugars I needed, but I ended up with an extra 1.5 gallons of wort in the kettle.  I boiled for about 2.5 hours in order to get down to my desired post boil gravity. 

For a discussion of DMS see brad's article:

http://beersmith.com/blog/2012/04/10/dimethyl-sulfides-dms-in-home-brewed-beer/

 
Some lighter beers use malts that are higher in S-Methyl methionine (SMM) which is the precursor to Dimethyl Sulfide (DMS). Boiling for 90 minutes or so is said to eliminate a majority of these compounds. DMS is considered a fault in most beer styles hence the desire to "boil-off" as much as you can.

This is not always necessary which lends to why you will see boil times in excess of 60 minutes usually only when those paler malts are used.

There are other reasons to boil longer - hitting gravity targets, for one - but the above is likely the most common reason.
 
There's also that whole kettle caramelization thing... mmm. caramels.
 
It is all an evil plan from Dr. Doofenshmirtz and the Tri-Valley Propane suppliers.


If not, it's what they said.
 
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