Newbie Q re: early/late malt extract additions

[Big_Belgian]

I'm brewing an amber tomorrow and just looking at a two different extract recipes (N.B.'s kit v Palmer's book) I noticed that (almost) the only difference between the two recipes is that one puts all the LME in at the beginning of the boil and the other has me adding half at the beginning and the other half with 15 min left.

I'm curious as to the reason one might add malt extract at the beginning, middle or end of a boil? I think I understand the reasons hops are added at different times, but not so much with the malt extract.

Also, what is the effect or reason to have a 90 minute boil (or, as one of my friends recently did, a 45 min boil)? What could one do in 90 minutes that would change the profile of the beer?

thanks!

BB

 

[JLem]

adding the extract late helps with hops utilization. adding all the extract up front results in a very concentrated solution, especially if you are doing a partial boil. the more concentrated the boil, the less hop utilization you get. Some people also add extract late to prevent the beer from getting too dark - the idea is that the sugars in the extract darken as they're heated - I'm not 100% convinced that this is a real issue, but, it may be an added benefit.

A longer boil can do a few things - if hops are added at 90min, you will get more bitterness since the longer you boil the hops the more bitterness you get; also, a longer boil drives off more DMS, which is especially important if you are using any pilsner malt; lastly, a longer boil will concetnrate the wort more, so you can end up with a higher gravity (of course, if you are topping off with water after the boil, this last point doesn't really matter)

 

[TTB-J]

Late extract additions are advisable if you are looking for a certain coloring in your beer. Often, when all of your extract is added at the beginning, you risk caramelizing it and creating a darker color than you expected. But adding extract at the beginning reduces the pH of your water, which, if it is too high during the boil, can result in astringent flavors coming from your hops. Thus, you want at least some of your sugars in the boil from the beginning. I do partial mashes, so I don't add any of my extract until knockout.

As for the reasoning of a 90 min boil, that is most likely for the purpose of increasing alpha acid isomerization in your hops. As you likely read in Palmer's book, boiling the hops isomerizes their alpha acids which creates bitterness to offset the malty sweetness from your extract. If you charted it on a graph, you'd see that the level of isomerization shoots up between 1 - 45 minutes and then begins to slowly level off. At 90 minutes, you've reached just about maximum isomerization, as the line is almost flat - and if you go much longer you risk actually reversing the process by degrading the alpha acids in your wort. So one could do a 45 minute boil and still get a decent amount of bitterness from their hops, which would be great if you were going for a sweeter style in the first place. 60 minutes is just the sweet spot, as it represents a very good rate of isomerization, but you would have to boil likely for another 30 minutes to get a noticeable improvement in the isomerization rate.

 

[Hang Glider]

+1. Coloring, hop utilization

60 minute additions of extract almost always end up with a darker beer than you'll expect, even with extra light DME