Whats up with a 90 minute boil?

[Milhouse]

I am brewing an all grain recipe for an oatmeal stout this weekend. The recipe calls for a 90 minute boil as opposed to a 60 minute boil. There will be a 90, 15, and 1 minute hop addition. What is the purpose for extending a boil to 90 minutes? What does this accomplish?

 

[sirsloop]

You can sparge with an additional ~.5 gallons and get a better efficiency...

 

[PvtSkippy]

Also useful in driving off DMS.

 

[BuffaloSabresBrewer]

Boil off more water to increase hop bitterness concentration and also extract more bitterness.

 

[Revvy]

There's been a couple of good threads in the last week that explain it....

If you do a search for them I'm sure you'll find it.

 

[Milhouse]

Thanks everyone for answering.

 

[gruversm]

Yes, I would agree if you're using Pilsner malt, you're driving off DMS with the 90 minute boil.