Partial Boil IBUs

[ayoungrad]

There have been prior posts on this subject and there are many discussions elsewhere on the subject.

However, I'd still like to hear people's opinions as there seem to be so many ideas out there:

Is 100 IBU a maximum of bitterness concentration or a maximum of human ability to detect bitterness?

If 100 IBU is a maximum of bitterness concentration then is it possible to achieve greater than 50 IBU from a half volume partial boil?

Also on the subject of hops... If you ferment without eliminating the break, will this increase IBU over the course of fermentation? Or will there be little to no effect because the hops have largely settled out?

Thanks in advance.

 

[McGarnigle]

I'm pretty sure that 100 is roughly the max detectable. It's not a limit to concentration.

Second question: You're really not going to get IBUs at that point as you need a boil to do that.

 

[pericles]

(1) The Brewing Network explored that question, and decided that 100IBUs (approximately) is the limit of the amount of alpha-acids you can dissolve into solution. I don't really have an opinion, but that's their claim.

(2) I understand your question, and it's clever. I'm certain that the answer is yes, since I have made partial boil IPAs with much higher than 50IBUs in the past. That - for me - casts doubt on the claim made by TBN!

(3) Leaving break material in the fermenter is essentially like dry-hopping, except your using spent hops. It might add some aroma, but not much.

 

[ayoungrad]

Thanks for the replies. I've also made partial boils that seem to have more than would be predicted by the 100 IBU max. I guess that's why I'm wondering about the break (which I sometimes dump into the fermenter and sometimes don't). My thought was that maybe acid conversion takes place during the boil but because the concentration of acids to too high during the boil, a portion precipitates out and subsequently redissolves with topping off.

Of course, none of this idea was based on anything except that I feel I have made batches with greater than the (100 IBU) x (Boil Volume/Final Fermentation Volume) theoretical maximum.