Double IPA Hop Utilization Question

hankevans42 · 01-15-2008, 01:23 AM

I plan on brewing the Northern Brewer Double IPA extract kit in the following week or two and I had some questions. Here's the inventory...

0.75 lbs Dingemans Caramel Pils
0.25 lbs Briess Caramel 120

3 lbs Pilsen Malt Syrup (60 minutes)
9 lbs Pilsen Malt Syrup (15 minutes)

1 oz Yakima Magnum @ 13.6% (60 min)
1 oz Centennial @ 9.5% (30 min)
1 oz Cascade @ 6.9% (10 min)
2 oz Glacier @ 6.1% (0 min)
1 oz Cascade @ 6.9% (dry hops)

I would like to do a full boil, and with the huge late extract addition I have no idea how much malt extract I should boil for 60 minutes to achieve the target bitterness (and I have no idea what the target bitterness is supposed to be). I tried using the bitterness calculation at howtobrew.com and came up with these rough numbers (I didn't factor in the specialty grain):

12 lbs for 60 min was app. 59 IBU
6 lbs for 60 min was app 86 IBU
3 lbs for 60 min was app 105 IBU

I was thinking it was supposed to be somewhere around 90 IBU's, so around 4 or 5 lbs for 60 minutes? Any advice from those with IIPA's under the belt would be greatly appreciated. Thanks!

GregKelley · 01-15-2008, 02:56 AM

BYO did an experiment showing that hop utilization is not affected by having malt in your boiling water. That being said, the site you are using is probably calculating IBUs as a function of how much total malt you have at the end in relation to how much hops you put in at what time and what the alpha % of those hops are.

So, if you are going to add all of the malt, whether it is at 60min, 15min or all at the end, you have to put that total amount in for your calculation.

The reason it suggests putting most of the syrup in at the end is to prevent carmellization and with it the darker color and different tastes.

Donasay · 01-15-2008, 03:17 AM

beertools.com has a bunch of different hop utilization calculators, the formulas all give out very different numbers, so pick one you like and stick with it for the sake of consistency across all your beers.

hankevans42 · 01-15-2008, 12:13 PM

According to the "How to Brew" website (Section 1 chapter 5.5), the boil gravity is a factor in hop utilization. Isn't this why I've seen multiple threads about reducing bittering hops 25% when doing a full boil as opposed to partial boil?

EDIT: I just used the beertools recipe calculator and it came up with 81.4 IBU's.

**Yooper** · 01-15-2008, 12:18 PM

Absolutely. If you do add the extract late, the bittering will definitely go up. That's because you get higher hops utilization in lower gravity wort. I'm not sure how much of a difference it makes in a full boil, though, since the gravity is already lower than it would be in a partial boil. Do you have Beersmith? That software has a box to check for late extract additions that would reallly help with the calculations.

**TexLaw** · 01-15-2008, 01:25 PM

If you are doing a full wort boil, don't mess around with the late extract addition.

TL

hankevans42 · 01-15-2008, 03:11 PM

Okay Tex, I just wanted to make sure that I had the right amount of hops for a full boil, being that Northern Brewer designed this kit for a partial boil and late extract addition. Looks like it won't be an issue...