Author Topic: IBU calculation confusion  (Read 5682 times)

papatom

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IBU calculation confusion
« on: August 22, 2008, 12:34:24 PM »
I have two very similar recipes which show very different IBU calculations.  How can recipe two with basically the same AA level hop and a longer boil time have less IBUs?

Recipe 1
Recipe Specifications
--------------------------
Batch Size: 5.00 gal     
Boil Size: 2.50 gal
Estimated OG: 1.052 SG
Estimated Color: 7.0 SRM
Estimated IBU: 16.1 IBU
Brewhouse Efficiency: - %
Boil Time: 40 Minutes

Ingredients:
------------
Amount        Item                                      Type         % or IBU     
6.00 lb       Wheat Dry Extract (8.0 SRM)               Dry Extract  100.00 %     
1.00 oz       Hallertauer Mittelfrueh [4.40 %]  (40 min)Hops         8.1 IBU       
1.00 oz       Saaz [2.00 %]  (2 min) (Aroma Hop-Steep)  Hops          -           
0.50 oz       Orange Peel, Sweet (Boil 5.0 min)         Misc                       
1 Pkgs        Belgian Witbier (Wyeast Labs #3944)       Yeast-Wheat               

********************************************************************
Recipe 2
Recipe Specifications
--------------------------
Batch Size: 5.00 gal     
Boil Size: 2.50 gal
Estimated OG: 1.050 SG
Estimated Color: 4.9 SRM
Estimated IBU: 10.0 IBU
Brewhouse Efficiency: - %
Boil Time: 60 Minutes

Ingredients:
------------
Amount        Item                                      Type         % or IBU     
0.50 lb       DME Wheat Bavarian (Briess) (8.0 SRM)     Dry Extract  7.69 %       
6.00 lb       LME Wheat Bavarian (Briess) (4.0 SRM)     Extract      92.31 %       
1.00 oz       Liberty [4.50 %]  (60 min)                Hops         10.0 IBU     
1.00 oz       Saaz [2.50 %]  (2 min) (Aroma Hop-Steep)  Hops          -           
1 Pkgs        Belgian Witbier (Wyeast Labs #3944)       Yeast-Wheat               

 

Offline bonjour

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Re: IBU calculation confusion
« Reply #1 on: August 22, 2008, 02:08:22 PM »
That's easy (especially if you have been there)

Identical recipes can show different IBU's if different formulas (BeerSmith has several available in the Options) are used.  Many brewers use Rager which I do not think is the BeerSmith default.

Fred

papatom

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Re: IBU calculation confusion
« Reply #2 on: August 22, 2008, 03:22:54 PM »
I am just using the default IBU calculator which is why this is confusing to me.  I check the boil size (same) and the OG (very close) I am not sure what else could alter the IBUs that much.

punkinatux

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Re: IBU calculation confusion
« Reply #3 on: August 22, 2008, 05:25:43 PM »
There appears to be an extra 8 ibus of bitterness in your first recipe from somewhere and i'm not sure where they are coming from.

What i mean is in your first recipe your hops are producing a total of 8 ibus for your hallertauer and 0 for your saaz where as your total IBUs comes out to  16.1, about 8 extra ibu's (perhaps something weird that is defaulted with your dry extract?) the last recipe only has 10 IBUs for the hallertauer, and the total is 10.

I'm not sure whats going on.

Offline wahoo

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Re: IBU calculation confusion
« Reply #4 on: August 25, 2008, 07:09:42 PM »
This is disturbing.  I have also seen IBU inconsistencies in the software and I fear I may have created overhopped batches as a result of not verifying Beersmith's calculations.  I notice it is worst with partial boils and/or late extract additions.

Offline wahoo

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Re: IBU calculation confusion
« Reply #5 on: August 25, 2008, 07:11:41 PM »
See below.  IBU=30.7  Sum of hop addition IBUs=28.2
 ??? ??? ???
 :-\
Very Special Original Bitter
Special/Best/Premium Bitter

 
Type: Partial Mash
 Date: 6/28/2008
Batch Size: 5.13 gal
Boil Size: 3.50 gal Asst Brewer: 
Boil Time: 60 min  Equipment: Stove Top with 5 gallon Cooler 
Taste Rating(out of 50): 35.0  Brewhouse Efficiency: 69.00
 
Ingredients
 
Amount Item Type % or IBU
1.00 lb Extra Light Dry Extract (3.0 SRM) Dry Extract 11.94 %
6.00 lb Pale Malt, Maris Otter (3.0 SRM) Grain 71.64 %
0.50 lb Caramel Malt - 60L (Briess) (60.0 SRM) Grain 5.97 %
0.25 lb Aromatic Malt (Briess) (20.0 SRM) Grain 2.99 %
0.25 lb Biscuit Malt (23.0 SRM) Grain 2.99 %
0.25 lb Crystal Malt, Dark, British (135.0 SRM) Grain 2.99 %
0.13 lb Chocolate Malt (450.0 SRM) Grain 1.49 %
1.70 oz Goldings, East Kent [5.20 %] (60 min) Hops 23.0 IBU
0.60 oz Williamette [5.50 %] (20 min) Hops 5.2 IBU
1.00 oz Goldings, East Kent [5.00 %] (0 min) (Aroma Hop-Steep) Hops - 
1 Pkgs Thames Valley Ale (Wyeast Labs #1275) Yeast-Ale 

 
 
Beer Profile
 
Est Original Gravity: 1.045 SG
 Measured Original Gravity: 1.045 SG
Est Final Gravity: 1.011 SG Measured Final Gravity: 1.011 SG
Estimated Alcohol by Vol: 4.43 %  Actual Alcohol by Vol: 4.43 %
Bitterness: 30.7 IBU Calories: 198 cal/pint
Est Color: 15.2 SRM Color: Color 
 

Offline UselessBrewing

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Re: IBU calculation confusion
« Reply #6 on: August 26, 2008, 09:25:40 AM »
The answer is actually quite simple.

In recipe 1 you picked the generic Wheat Dry Extract (8.0 SRM). In recipe 2 you picked a specific supplier (Briess).
Generic extract has "Equivalent Hops in Extract" added in the extract and the Briess extract does not. BeerSmith is merely taking that into account and reporting it in the total IBU. If you know that you are going to use a specific supplier's (Like Briess) extract you should add that to the recipe in order to get the correct IBU.

Hope this clears up some of the confusion!

Cheers

Preston
The woodpecker pecks, Not to annoy, But to survive!

 

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