Why do all grain recipes use fewer hops?

[gio]

I have the book "beer captured" and it has extract recipes with all grain versions for all recipes in the book. The AG versions all use fewer hops (about 20-25% less) even when they are boiled for the same amount of time as the extract version. Why is this? Does it have to do with the additional water used for the AG recipes? Why would more water mean you need fewer hops?

 

[frazier]

You get better hop extraction from a lower-gravity boil. In AG recipes, your boil starts out significantly larger, therefore lower gravity, than an extract recipe.

 

[Maxkling]

With 3 gallon boil extract recipes you use roughly 25% more hop because your only boiling the bittering hops in 3 gallons of water. All grain your doing full boils thus not needing to make up for the top off water.

Same if you were to go with full boil extract.
https://www.homebrewtalk.com/f37/full-boil-extract-steep-what-adjustments-do-i-make-47770/

 

[HexKrak]

From How To Brew by John Palmer

It is the gravity of the boil (1.080) that is used in figuring the Utilization. As you will see in the next section, hop utilization decreases with increasing wort gravity. The higher concentration of sugars makes it more difficult for the isomerized alpha acids to dissolve. I use the initial boil gravity in my utilization calculation; others have suggested that the average boil gravity should be used. (The average being a function of how much volume will be boiled away during the boiling time.) This gets rather complicated with multiple additions, so I just use the initial boil gravity to be conservative. The difference is small—overestimating the total bitterness by 1-3 IBUs.

 

[SumnerH]

From How To Brew by John Palmer

Palmer's since retracted that and apologized for spreading misinformation (see BBR's interview with him "What is an IBU, Really?" for one source).

Hop utilization is largely independent of boil gravity.

BBR conducted actual measurements of the IBUs in 3 beers, one with a boil gravity of 1.127, one with late extract addition for a boil grav of 1.077, and one with a full boil at 1.068.

The same hopping schedule was used for all 3, and hop utilization is identical for all 3; the March 4, 2010 - BYO-BBR Experiment III:
http://www.basicbrewing.com/index.php?page=radio

(it also confirms that late addition can help make a lighter beer, though the effect is small).

There are some legitimate effects from isoalphas adsorbing to break material that are correlated to the boil gravity and can affect hop utilization, but they appear to be relatively minor with extract brews (as the above numbers show) which makes sense given the much smaller amount of break material in extract vs. all grain.

https://www.homebrewtalk.com/f128/estimating-bitterness-algorithms-state-art-109681/ has more discussion.

 

[HexKrak]

Well dang, ya learn something new every day (especially around here). It's pretty crazy to see all the beer calculus that the various experts are using, and pretty much all of them report back higher numbers than was accurate. Initially I thought it had something to do with the solubility levels of the acids, but then I read How to brew, and now I'm just all mixed up.