Adding extract late in the boil vs hop utilization

[thatshowyougetants]

I've read many people on these forums claim that you can (and should) add your extract late in the boil. Claimed advantages are that the resulting beer will be lighter in color and have less of that mysterious 'extract twang'.

I'm reading John Palmer's How To Brew and according to the section on Hop Utilization there is a clear and non-trivial relationship between boil gravity and hop utilization (and therefore IBUs of the finished beer).

For example for a 60-minute bittering hop boil the utilization with a gravity of 1.03 is 0.276 while with a 1.05 gravity it's 0.231. If you extrapolate to a gravity of 1 (boiling the water without extract) the utilization would be approximately 0.34. This could make a difference of about 16 IBUs in the final beer (using Palmer's example of a 9.6 AAU 60 minute boil).

If I'm interpreting this incorrectly please feel free to correct me. But it seems that nobody should be advocating adding extract late in the boil without warning that IBUs will be significantly affected.

 

[DenverUSMC]

https://www.homebrewtalk.com/f37/late-addition-hop-utilization-188394/

Interesting thread that addresses hop utilization, including Palmer mentioning that he was incorrect in his book; he discusses the topic at about the 37 min mark:

March 20th 2008 recording
http://www.basicbrewing.com/index.php?page=basic-brewing-radio-2008

 

[Pelican521]

I'm just a noob with a handful of batches under my belt but after researching this topic quite a bit and reading a Q&E on Midwest brewing's website I found if doing a late extract addition you should reduce your bitter hops by about 20%.

I did this on my last two batches, a brown ale and an oatmeal stout that I did late additions.

 

[thatshowyougetants]

https://www.homebrewtalk.com/f37/late-addition-hop-utilization-188394/

Interesting thread that addresses hop utilization, including Palmer mentioning that he was incorrect in his book; he discusses the topic at about the 37 min mark:

March 20th 2008 recording
http://www.basicbrewing.com/index.php?page=basic-brewing-radio-2008

Thanks, I listened to the recording. Palmer doesn't say the effect on IBUs isn't there, merely that the mechanism is different than he described, and the magnitude of the effect may be lower than described in his book.