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-   -   AAU Calc. vs Beer Smith AAU Calc. (http://www.homebrewtalk.com/f39/aau-calc-vs-beer-smith-aau-calc-122577/)

C2H6O 06-05-2009 07:56 PM

AAU Calc. vs Beer Smith AAU Calc.
 
According to Palmer's book you can calculate the AAU's by multiplying the % and weight. So my Galena hops are 10.1% and the recipe calls for 6 AAU's. I plan to add .6 oz. When I plugged these values into beer smith it came out at 1.2 AAU. Can someone explain to me the discrepancy?

Yooper 06-05-2009 08:11 PM

Quote:

Originally Posted by C2H6O (Post 1365524)
According to Palmer's book you can calculate the AAU's by multiplying the % and weight. So my Galena hops are 10.1% and the recipe calls for 6 AAU's. I plan to add .6 oz. When I plugged these values into beer smith it came out at 1.2 AAU. Can someone explain to me the discrepancy?

Different boil times/gravities. What do you have set for the boil volume and time? A 60 minute boil would give you much more IBUs than a 5 minute boil, for example, and a higher SG wort will give you less utilization.

C2H6O 06-06-2009 02:15 AM

Total batch size is 5 gal. Initial boil is 2 gal for 60 minutes. The OG = 1.045.

feedbag 06-06-2009 02:19 AM

I think you have your AAU's confused with your hop utilization, or what it contributes to your IBU's (this is what I believe BeerSmith is showing you). Check out How to Brew again, Chapter 5 section 4 here: How to Brew - By John Palmer - Hop Measurement. This might clear it up for you.

HairyDogBrewing 06-06-2009 03:07 AM

Quote:

Originally Posted by C2H6O (Post 1365524)
According to Palmer's book you can calculate the AAU's by multiplying the % and weight. So my Galena hops are 10.1% and the recipe calls for 6 AAU's. I plan to add .6 oz. When I plugged these values into beer smith it came out at 1.2 AAU. Can someone explain to me the discrepancy?

Your formula is for HBU's - Home Brew Units.
It was in Joy of Homebrewing, too.

It's a way to compare the relative bitterness of recipes,
but it ignores a lot of variables such as boil gravity and boil time.
Tinseth, Daniels, and Rager formulas are much more complex, and yet each is still only an approximation of actual IBUs.

C2H6O 06-06-2009 09:55 PM

All - Thanks for the replies.


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