What does a 90min boil do?

What does a 90min boil do that a 60min doesn't? I see some recipes that look to be almost identical in the grain bill but one calls for a 90min boil and one calls for a 60min boil. Both end up with 5.5 gals of wort.

Personally I do 60 minute boils, but my understanding for a 90 minute boil is to boil off more wort, you will get higher IBU's from 90 minutes of boiling hops, and if you are using a lot of Pilsner malt, the 90 minute boil helps drive off DMS and precursors.

There may be more that it does, I'm just not sure.

here's a good thread dealing with this same question:

https://www.homebrewtalk.com/f14/90min-vs-60min-boil-87058/

Reduces water volume...

Or if I get too busy and loose track of time.

As for Ending with 5.5gal at the end or a 60 and a 90min boil thats just all in your Evap loss. Adjusting your Water will allow this to happen...

One of the biggest reasons people do 90 minute boils besides those already mentioned, is to blow off DMS precursors, which if not boiled off can give beer a distinctive, and unpleasant cooked corn aroma and flavor.

This is really important if there is a large amount of Pilsner malt in the grainbill.

In terms of hops utilization, when we do 90 minute boil generally we boil for 30 minutes, THEN start our hop/countdown for the 60 minute boil and additions. I usually set my timer for 30 minutes, when it goes off I drop in my 60 minute addition, then reset my timer to 60 and start the clock.

This gives you some info on DMS http://www.picobrewery.com/askarchive/dms.htm

My next batch/recipe actually calls for a 70 minute boil. Why, you might ask? Why the F*&^ not? Who are you calling a psycho!!!???!!!

Boiling longer also adds some more carmalization of the wort, if that's what you're going for with your recipe

mrtrav said:

Boiling longer also adds some more carmalization of the wort, if that's what you're going for with your recipe

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That's not really an issue for All Grain batches...in fact most of the lightest styles of beers require 90 minute boils... again, most of those that require large amounts of pilsner malt. And most of them tend to be extremely light (in color or body) lager recipes, including dortmunders amd even belgian saisons. And those are really golden yellow in color, so you don't get a lot of caramalization.

You can also caramelize some sugars and darken the wort a little with a longer, vigorous boil times.

Beernik said:

You can also caramelize some sugars and darken the wort a little with a longer, vigorous boil times.

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When brewing extract batches this is true.