I’ve noticed that a lot of veteran brewers employ a 90 minute boil. Aside from driving off DMS and increasing wort carmelization are there any other benefits?
-J.K.L.
Longer boils tend to darken the wort and there are maillard reactions taking place producing more melanoidins that enhance the maltiness of the wort. Not to mention increased hop isomerization or enhanced hop bitterness. The longer boil also concentrates these flavors that are created during the boil. Driving off DMS is probably one of the biggest reasons to boil longer but these other attributes also come into play as well.
If I’m using pils malt, I’ll go 90 minutes to drive off the DMS. I also use a 75 minute boil with non-pils grain bills as well, just so that I have 15 minutes to get the hot break before I add any hops, reducing the risk of boil-over.
Technically speaking, you can’t get caramelization in the boil. And melanoidins are colors, not flavors, so they won’t enhance the maltiness of the wort.
Agreed they are are brown, high molecular weight heterogeneous polymers.
They are an integral part of the maillard reaction which enhances maltiness. When sugars and amino acids combine (through the Maillard reaction) at high temperatures there’s nonenzymatic browning similar to caramelization. In the process, hundreds of different flavor compounds are created.
Agreed on all counts…I was in pedantic mode!
;D
OK,
so what happens to the sugars (solids) when the water they are being carried by suddenly disappears into a cloud of water vapor?
Traditionally caramelization occurs when water is removed and the resulting sugars heat up, as in making candy.
Yes, you need to remove enough water for the temperature to get hot enough for the sugars to caramelize. We never reach that point with wort. For example, maltose doesn’t caramelize until over 350F. Glucose around 320F. Wort - 212F. Your wort might hit 215F though Fred. 
I found this cool boiling point calculator. Enter the brix, it tells you the bp.
Is “pedantic hippy” an oxymoron? Hmmm, need to ponder that over a beer.
Once upon a midnight dreary
While he pondered weak and weary
Over many a pint of quaint and hoppy brew
While he nodded, nearly napping, suddenly there came a tapping
As if some gentle hippy came tipsy to correct his point of view
Tis some pedantic hippy
Only this and nothing new.
Yeah, that’s what I meant to say but I didn’t want to confuse anyone. 
-J.K.L.
Good idea…I’ll join ya!
You RAWK!!
Ninety minutes produces about the maximum isomerization potential for alpha acids in wort according to work by Malawicki and Shellhammer. Beyond that time, the isomerized alpha acids are broken down to a slight degree and the bittering actually decreases. In terms of energy efficiency of converting alpha acids to iso-alpha acids, a boil time in the 60 minute range is better than 90 minutes.
+1
If pils is 50% or more of my base malt, I’ll boil for 90 minutes to alleviate DMS concerns. Otherwise, I boil for 70 minutes (10-minute hot-break period).
Do you not get carmelization at the bottom of the pot? I would think the bottom would get much warmer than boiling, but not sure how much more…
Maybe. :) The pressure won’t be sufficient to cause the temperature rise, and it’s the sugar that has to be hot enough, not the kettle. I don’t the physics well enough to know for sure.
What would happen to fermentability if it did carmelize? I was recently trying to brew a very small batch to do some mash experiments, and while I used a very low boil, I nevertheless reduced the wort to sludge. It didn’t look or smell burned, but the gravity was off the scale of both my hydrometer and refractometer. Perhaps I actually made extract. :P So I diluted it back to a reasonable gravity and pitched. But no fermentation. If I thoroughly carmelized the wort, would that remove the fermentables?
Fermentability goes down as the sugars caramelize. I really can’t say for sure what you did though.