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IBU's

merleti

Apprentice
Joined
Feb 22, 2014
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I'm noticing the IBU's on my Beer Smith to be different than expected. I loaded a recipe from online and the IBU's said it would be 11.9. Beer Smith has it at 18.4. Am I missing something?
 
There are three major systems used to estimate IBU's:
Tinseth
Garetz
and Rager

If the online version uses a different system than you used in BeerSmith, then it won't be the same.  Look at the lower right of your design tab and see if any of them are close to 11.9 IBU's.  If one of them is, it's likely that the author used that system for estimating IBU's.

Another possibility is that your Alpha Acid % is differen that what the online designer used for calculating IBU's.

It's also possible that both are occurring.
 
Garetz has it at 8.4 and Rager has it at 16.2.
I'm using the same manufacture of hops.
 
I adjusted it to the manufactures specs and I get Garetz 8.6 and Rager 16.8
 
merleti said:
Garetz has it at 8.4 and Rager has it at 16.2.
I'm using the same manufacture of hops.

Hop Alpha Acids are not all the same.  They change from season to season and from farm to farm.  You have to know what the online recipe designer used for Alpha Acid calculations and what you actually were able to purchase.  I've got Cascade hops in my inventory right now that are of different %'s Alpha Acids.
 
Another factor is batch volume. The online recipe might be 5.5 gallons onto the fermenter, while yours may be 5. This is why it's important to start with the writer's equipment profile, then scale the recipe to yours.
 
Thanks for all your help. I didn't even think of it being a different season of hops. Guess I got caught up chasing numbers. Thank you again.
 
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