changing boil size effect on IBU's

[hotpants]

Hey,
So Im doing a recipe that calls for a 3.5 gallon boil, but I can only do a 3 gallon boil tops. If I lower the boil down how much will this affect the character of the beer? Should I consider just scaling the batch down?

Recipe:

BELL'S OBERON ( 5 gallons, 3.5 gallon boil )

- 3 LB, 4 OZ Briess Bavarian Wheat DME
- 2 LB, 8 OZ Briess golden light DME
- 10 OZ Munich
- 6 OZ Crystal 60L
- 3/4 OZ Hallertauer pellets (60 min.)
- 1 OZ Hallertauer pellets (30 min.)
- 1/2 OZ Saaz pellets (15 min.)
- 1/2 OZ Saaz pellets (5 min.)
- Culture yeast from Oberon bottles or use WLP320 (American Hefeweizen)
- dry hop 7-14 days with 1 OZ Cascade leaf hops


Cheers

 

[rodwha]

It would lower your IBUs. Easiest would be to scale down.
Free beer calculator at hopville.com

 

[hotpants]

It would lower your IBUs. Easiest would be to scale down.
Free beer calculator at hopville.com

Lower my IBUs by adding less hops during the boil?

 

[TarVolon]

It will lower your IBUs by giving you less utilization efficiency (or whatever you call that), if I understand correctly. If you add some of the extract at flameout, you might counterbalance it.

 

[DarthMalt]

You would need to increase the amount of hops you add if you decreased boil volume, not decrease IBU's. You'll want your IBU's to remain the same throughout the entire process, since the malt/bitterness balance of the beer is based on the # of IBU's in the recipe.

Since you are deceasing your boil volume, your utilization will also decrease. This means you need to add more hops. You can plug the recipe into Beersmith if you have it and figure this out. If not, there are some free recipe calculators available online.

Or, you can just scale the entire recipe.

A late extract addition may also help, as mentioned above. In that case, you probably wouldn't need to change the hops much at all.




EDIT: I'm at my work computer, otherwise I'd be able to help you a bit more with this ie. exact amounts/differences. However, a half gallon difference in boil volume won't change much in the way of IBU's.

 

[DonutMuncher]

If the recipe calls for 3.5 gallons and you're going to scale down to 3, I probably wouldn't mess with scaling the hops much.. I don't think your utilization change will be that drastic.

But TarValon is correct, instead of boiling all of the extract required by the recipe, you could save some of it, and add it at flame-out when you stop the boil.

The hop utilization gets out of whack if you have too much malt in a smaller amount of water (i.e. a high-gravity boil).