Does the time extract is added affect IBUs?

[booherbg]

Hi. Simple question. I've read that higher gravity makes isomerization of hops less efficient. I also notice in my hopville calculator that the IBUs can change substantially if I have, say, 60% extract vs 0% extract.

If I added extract at 60min, there would be no harm because it would be present the whole boil.

But if I add at 5min, all the hops have been isomerizing at a much lower gravity and hence the IBUs will be calculated as if there is no extract at all.

I'm confused now. Does anyone else take this into consideration?



If I can get 80IBU for the same hops as my 50 IBU recipe only by adding extract at the end of the boil, isn't that pretty important? Most recipes simply mention you can add the extract any time - the later the better often times.

 

[Skyforger]

Yes, your IBU's will change. You need to take that into consideration. If you add extract near the end, you could just calculate the IBU's as if there were no extract for the entire boil and get pretty close. Otherwise, you could calculate the time the hops spend with and without extract separately, then add them. Unless you're adding the extract halfway through the boil, though, I would see no reason to do that; IBU's aren't the most deterministic of measurements anyways.

The difference won't be huge, except with really bitter beers. Maybe that's why many don't worry about it. A difference of, say, 3 IBU's is not too practically relevant. 10 might be.

 

[captwalt]

I actually did this once with two identical batches. late addition of some of the extract definately increased the bitterness. I'm not sure how to calculate it though, but it was definately bitterer.

 

[booherbg]

that makes sense and confirms my suspisions. so it's possible that my 90IBU is actually much higher than that. hah. oops!

 

[hoppymonkey]

that makes sense and confirms my suspisions. so it's possible that my 90IBU is actually much higher than that. hah. oops!

It does matter as everyone stated above, but there is a ceiling of bitterness at about 100IBU so it won't make much difference in this particular beer if it was supposed to be 90IBU.

 

[booherbg]

It does matter as everyone stated above, but there is a ceiling of bitterness at about 100IBU so it won't make much difference in this particular beer if it was supposed to be 90IBU.

i've heard that too. so what happens to the extra hops that you add? Do they just not isomerize and add to flavor? Or if you add more water later, is there somehow that the isomerization can still occur due to the "hop stuff" thats in the water? I imagine that's not the case since you probably need the heat of the boil. Just wondering.

is there a way to quantitatively measure bitterness?

 

[Bobby_M]

That was once conventional wisdom but...

https://www.homebrewtalk.com/f13/partial-boils-latest-basic-brewing-radio-podcast-166353/

 

[hoppymonkey]

i've heard that too. so what happens to the extra hops that you add? Do they just not isomerize and add to flavor? Or if you add more water later, is there somehow that the isomerization can still occur due to the "hop stuff" thats in the water? I imagine that's not the case since you probably need the heat of the boil. Just wondering.

is there a way to quantitatively measure bitterness?

There is a huge thread on here about it for a more detailed description of the brew science. If you add more hops, you can still get a flavor change, but not get additional IBUs. Isomerization only occurs while boiling and can only reach a certain per liter threshhold before maxing out and rate begins to decline arround 70IBUs.

 

[booherbg]

That was once conventional wisdom but...

https://www.homebrewtalk.com/f13/partial-boils-latest-basic-brewing-radio-podcast-166353/

i'll have to check that out, thank you.