why 90-min boil if no pilsner malt?

Drive hot break to completion.

 

Get the most alpha acids out of bittering hop additions for budget minded brewers and/or get more evaporation for brewers struggling to hit 8% over the course of a 60 minute boil...

 

I've read about longer boils to try to caramelise some of the sugars in the wort, but i'm not entirely convinced this is based on science...

 

All the above + Waste 50% more propane/insert fossil fuel of choice

(cause that's the way we've always done it)...lower volume...hit your OG???

 

squeak out a few more gravity points?

 

London Porter brewers had very long boils, sometimes as long as 3 or 4 hours.

 

Several reasons for a 90 minute boil:
1) to enhance color characteristics
2) to increase gravity points
3) to increase bitterness and or decrease flavor and aroma from hops
4) to increase melanoidin Flavors
5) slight Caramelization of sugars
6) used to mimic increasing efficiency in bigger beers (more sparge water/longer boil to hit target)
7) to drive off DMS precursors
8) to increase malliard reaction and flavors from said reaction

That's about all so can thin of but I am sure there are a few more things happening in a 90 min boil that aren't in a 60 minute boil.

Slainte!

 

One negative of an extended boil (3-4 hours) is that proteins are denatured which will impact the beer foam (poor head retention).

Cheers!

 

For me, it's a buck of grain or a buck of propane. Time is Money!

 

Why?

 

Time is money*, and I'd rather not burn more fuel than necessary. I agree that the supposed benefits of a longer boil are not readily apparent (does not apply to pilsner malt). They may be scientifically quantifiable, but if such quantifications between a 60 and 90 minute boil have been made, I am not aware of it (mainly because I haven't searched for such results). I would speculate wildly that any such quantifiable differences between otherwise identical beers done 60 and 90 minutes would require some sort of analyzer with sensitivity much higher than human smell or taste or sight could detect.

*Well I should probably clarify that. Time is money if you have a job. If you're a perpetual student like me, time is just something to facilitate procrastination when you should be studying. Money has little to do with it.

 

Hmmm.... Might need to do a small batch experiment in the future. Same base wort, one batch boiled for 60 mins, one boiled for 180 mins, then both topped up to the same OG & see what (if any) differences in the finished product.

 

Colour, wort concentration.

 

This is the only answer for this thread. Fantastic summary of the reasons why longer boils are beneficial.

 

Pretty good list, but one small correction... It's not actually the DMS precursor (SMM) that's driven off by the boil. It's the DMS that mashing and heating the wort has converted from SMM to DMS that is driven off by the boil.

 

Well, I will be "that guy". Vikeman was correct on the DMS vs SSM.

Enhanced color comes form the formation of Melanoidins. Melanoidins are the end products of Maillard reactions. Number 1, 4 and 8 are all related. Some also say that Melanoidins have little/no flavor, and the Maillard products are what have the flavors - I don't know if that is all understood or not.

Number 5 is another that I wonder about. You might get some caramelization at hot spots in a direct fired kettle, but from what I have seen that will only be at a temp that would caramelize fructose. With nucleate boiling you could get a little more going on. Pro brewers that use steam fired jackets or calandrias will not have any or only small caramelization as the steam is not hot enough to cause much if any caramelization.

 

Here is an excellent article about boiling (and boil length) written by Bill Pierce: http://byo.com/recipes-tag/item/249-boiling-advanced-brewing

Cheers!

 

Here's a link to the Nov-Dec issue of the Michigan Beer Guide which has an article about the optimum length of the boil - http://www.michiganbeerguide.com/?currentIssue (if the link does not go directly to the article, it's on page 30). The author writes a brewing article in every issue of this magazine, usually from the scientific perspective, and I think that he is a scientist by trade for his regular job, but I don't know any further what his credentials are. However, his writings are always very good and make sense to me, primarily because they are written in layman's language.

In the article, he does not arrive at a final answer for the optimum length of the boil, but he does a great job discussing each of the factors that need to be considered when deciding on the boil length. It's a short read and very informative.