Hop bitterness and cooling

Hey all,

My current setup is not complete but still functional. One of the things it's lacking is a great cooling system. I still brew with it and get good beer... just takes awhile to cool. Hopefully I'll have this remedied soon, but it's not like that one imperfection is going to get me to stop brewing...

Bitterness from hop additions, of course, depends on boil time... isomerization and all that, I get it. Now the 60+ minute hops are pretty much fully utilized and won't be affected by minor changes. But in late-hopped beers, you'll see recipes with additions at 15, 10, 5, 1, 0 (flameout). Obviously there is a noticeable distinction here, otherwise there wouldn't be so many hop additions.

So my question is, does the bitterness really stop getting extracted the moment you turn off the flame? Or do the hops continue to slowly provide more bitterness the longer the wort still is hot? For some reason I don't see it being something that turns "on" at 210 degrees but doesn't happen at all at 205 or something.

I guess the short version of what i'm asking here is, if I boiled a 10 gallon batch, cooled 5 gallons quickly and 5 gallons slowly, fermented them separately under like conditions, would I expect the slower-cooled one to have more IBUs than the other?

Hey Dougan:
I'm sure the real pros will come in with the more exact answers, but I can tell you hops definitely do not stop bittering at flame out. As you suspect they continue to release bitterness as the wort cools. The lower the temp gets the slower they bitter.
If one of your 5 Gallon batches remained hot longer than the other, yes it stands to reason it would have more IBU's than the other, assuming the hops remain in the wort as it cools.
To help combat this you might try adding your hops as whole leaf in a sock, and removing the socks at the same time from the entire batch. This should keep the hop signature fairly similiar in both halfs of the batch.
Still a good idea to get that second batch under 100 as soon as you can though.

from my understanding of hops, no the bitterness does not stop being extracted the minute you stop boiling. The hotter the temperature the more bitterness from the hops is extracted. At lower temperatures (ie. first wort hop) you extract different amounts of compounds. Some people put boiling water into a french press with hops to make a sort-of extract. If you were to make that same "extract" with 180 degree water you will still be extracting flavor however the IBU's should be less...