Alpha acids and IBU limits

[kaconga]

So I know that alpha acids isomerize into IBUs when boiled. I also know that there is a practical limit of ~100 IBUs in any given quantity of wort/beer. But I am curious as to what happens to the alpha acids that don't isomerize. If I were to put a theoretical 150 IBUs worth of hops in at 60 min then in reality I would only pull around 100 IBUs, so what happens to the remaining acids?

 

[kaconga]

Anyone?

 

[Denny]

So I know that alpha acids isomerize into IBUs when boiled. I also know that there is a practical limit of ~100 IBUs in any given quantity of wort/beer. But I am curious as to what happens to the alpha acids that don't isomerize. If I were to put a theoretical 150 IBUs worth of hops in at 60 min then in reality I would only pull around 100 IBUs, so what happens to the remaining acids?

I believe 100 IBU is the taste threshold, not the limit for measurable IBU.

 

[Yooper]

I believe 100 IBU is the taste threshold, not the limit for measurable IBU.

I do think that about 100 IBUs is the limit of isomerization as well.

I'm not sure what happens exactly when the wort's saturation is reached, but I do know that when I make a Pliny The Elder clone, I have an "oil slick" on top of my wort, and I have to assume that it is hops oils.

 

[kaconga]

Well at least I know I am in good company on this subject. I started thinking about this because I saw a 4 oz bittering charge in a recipe and it would have been approximately 200 IBUs. However I know that 100 was about the practical limit and I wondered if there was any gain in those extra acids being in the wort.