Author Topic: IBU Discrepnancy  (Read 5273 times)

Bprind01

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IBU Discrepnancy
« on: September 20, 2009, 04:31:37 PM »

Beersmith's IBU default setting is supposedly Tinseth. However, if I open the Hop Bitterness icon on the left hand side of the screen and calculate the same hop bill under Tinseth setting, I get a completely different IBU calculation for my recipe. For instance, my recipe IBU's come out as 56.5 but if I open the hop bitterness page and input the same hop bill, I get 75.5 IBU's. Which one should I trust as both should be Tinseth calculations?

Offline MaltLicker

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Re: IBU Discrepnancy
« Reply #1 on: September 20, 2009, 04:56:06 PM »
Top three numbers the same too?  Especially batch size and boil volume?  I've under-IBU'd by using too much water and ending up with more wort than BeerSmith planned for.

Offline bonjour

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Re: IBU Discrepnancy
« Reply #2 on: September 21, 2009, 06:24:41 AM »
IBU Discrepnancies are the norm if you use different formulas (the above posters are not having this issue).

The important thing is that you use the same formula consistantly and adjust your hops to what your tastebuds say.  Any of the formulas will put you in the ball park, to make award winning beers you must adjust to taste.  Everyone's system and methods, while similar, are different,  and these differences will impact bitterness, flavor and aroma of hops.  FYI all Jamil's recipies use the Rager formula both in the book and online (http://beerdujour.com/JamilsRecipes.htm).

Fred

Offline MaltLicker

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Re: IBU Discrepnancy
« Reply #3 on: September 21, 2009, 06:48:56 AM »
I tested it and got diff results as well.  Rager on both, no FWH.  Glacier 5.9%AA, 0.25 oz drops.

Batch size 5.25 gals
Boil Volume 7.32 gals
OG 1.048

            recipe               tool
60           5.7                 5.7
45           5.1                 5.6
30           2.9                 3.2


I then boosted all drops to 1.0 oz, and the 45 and 30 min drops varied again.  In the tool, the 60 and 45 IBUs were identical, so I suspect the tool is not working right.  And when I switched to Tinseth, all three IBUs varied between recipe and tool. 


« Last Edit: September 21, 2009, 07:02:27 AM by MaltLicker »

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Re: IBU Discrepnancy
« Reply #4 on: September 21, 2009, 07:44:08 PM »
The differences usually come from the equipment settings.  The hop tool makes some assumptions about what I might call "average" equipment settings and attempts to use zero losses for water losses, an average value for mash tun specific heat, mash tun volume, etc to back out the gravity of the boil and other factors.  In contrast the recipe version of the IBU calculation uses the actual equipment settings from your equipment profile which are generally more realistic and also more accurate.

  As a result the hop tool is less accurate than the recipe IBU calculator, but I felt it would be painful to have a person enter all of the possible equipment settings into the hop tool to get a more accurate calculation.  It seemed to be reasonable to make some assumptions and provide a close, but less than perfect answer to keep the tool relatively simple.  However, the recipe IBU calculator is more accurate.

Cheers,
Brad
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Offline baj475

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Re: IBU Discrepnancy
« Reply #5 on: September 21, 2009, 08:36:58 PM »
Seems like there would be a simple solution in adding an option to hop tool to use average values or the user's specific equipment.

 

modification