AAU Calc. vs Beer Smith AAU Calc. - Home Brew Forums

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Old 06-05-2009, 07:56 PM   #1
C2H6O
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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?

 
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Old 06-05-2009, 08:11 PM   #2
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Quote:
Originally Posted by C2H6O View Post
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.
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Old 06-06-2009, 02:15 AM   #3
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Total batch size is 5 gal. Initial boil is 2 gal for 60 minutes. The OG = 1.045.

 
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Old 06-06-2009, 02:19 AM   #4
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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.

 
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Old 06-06-2009, 03:07 AM   #5
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Quote:
Originally Posted by C2H6O View Post
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.

 
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Old 06-06-2009, 09:55 PM   #6
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All - Thanks for the replies.

 
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