Hops and hitting IBU numbers

[thumpersk_a]

Quote:
Originally Posted by CSI View Post
Chimay Grande Réserve (Blue), TRIAL 001

This initial recipe was drafted from BLAM and the Chimay Blue label declaration of ingredients, (water, malted barley, wheat, sugar, hops, yeast). Where ingredients like "caramel malt" were generalized in the literature we based the malt selection on color characteristics and region for roast and quantity *e.g. Belgian Caramunich contributes a distinct ruddy color and does not raise the SRM overly high (as would Special B). The selection of Belgian Candi Syrup and the quantity was also based on BLAM, (adjuncts did not exceed 5% in the Chimay Red). 1lb of D-45 equated to 6.4% of fermentables and brought the color up to a ruddy-brown, (however), after 6 months of fermentation the SRM was approximately 13-14. The recipe below will be lighter than the CGR. If you use 1lb of D-90 the SRM will be much closer to the CGR.

OG: 1.077
FG: 1.008
ABV: 9.00%
SRM: 13+ (from BLAM adj, but the actual Chimay pours closer to 16-17)
IBU: 31.4 (Tinseth)
VOL: 5.25 gal
BHE 75% (assumed)

FERMENTABLES
12.0 lb Belgian Pils
1.00 lb Dingeman's Cara 45
1.00 lb Torrified Wheat
1.00 lb D-45, (or 1.00 lb D-90 for Darker SRM) Candi Syrup, Inc.

HOPS (30.4 ibu)
Saaz 1.50 oz,60 min (Brewery visits indicate Nugget is the bittering hop now)
Hallertau 1.50 oz,20 min

YEAST
WLP 500 (Chimay) – 260 Billion Cells (pitched at high krausen, 22 hrs)

MASH
Sacch 148F 60 minutes
Mash out 170F 20 minutes


90 minute boil. Chill to 64F. O2 for 60 seconds. Ramp primary starting at 64F then raise to 68F over 6 days. Secondary at 60F until FG is reached, then crash at 38-40F until ale clarifies. Prime with Golden Candi Syrup at a rate of 30 grams/gallon (then hold bottles at 72F for 10 days for initial carbonation). Bottle condition at cellar temps for (a minimum) of 12 months.


This is a link to Chimay.com showing a video of the pour, color, and head:
http://www.chimay.com/en/chimay-bleu...DC=287&IDD=130
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Cheers,

AJ[/QUOTE]



I am brewing this recipe and am unfamilliar with hitting ibu numbers. This recipe uses 1.5oz saaz 4.5aa and 1.5oz hallertau 5.25aa for total IBU 31.4

I ordered the hops by name and the saaz is 3.0aa and the hallertau is 3.1aa
In order to hit the IBU numbers i have to use 2.0oz of each.
My question is will using the 2oz of each type of hops to hit 32.03 IBU have the same flavor as using hops with the higher alpha acid rating.
Not sure how alpha acids work. Do more hops of the same species of a lower alpha acid equal the same flavor of same species of higher alpha acid but lower quanity? Maybe im over thinking this and should just use the hops i have and enjoy. Thank you all for any help

 

[Oginme]

You can match the same AA value for each addition if you want to closely mimic the recipe as given. For instance, your Saaz addition is 1.5 ounces at 4.5% AA fir the first addition. Your Saaz are at 3.0% AA. Scale them by simple proportions: The recipe adds 1.5 oz * 4.5% = 6.75 AAU (alpha acid units). 6.75 AAU/3.0 (the AA of the hops you have) gives 2.25 ounces of your Saaz hops for this addition. You can do a similar calculation for the second addition.

In reality, the calculation for IBU is an estimation which has quite an error built in already. If your actual results are within +/- 5 IBU, you will be doing quite well. You may be pretty close with what you have already and straying too far with the amounts in the original recipe will give you a different hop character (though with the last addition being at 20 minutes, it'll probably be small (IMHO).

 

[thumpersk_a]

Ok thank you for your help