Adapting late hop additions to AA%

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LovesIPA

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Let's say I have a recipe that calls for:

A bittering charge of Columbus
1 oz of Cascade at 15 mins
1 oz of Cascade at 5 mins
2 oz of Cascade at 1 min

I brewed this beer about 6 months ago with Cascade that was 5.5% AA. Since then I went through a pound of Cascade and bought another pound but this one is 7.1% AA.

So the question is, what is the proper way to account for the difference in alpha acids when adding flavor/aroma additions? Do you scale the late additions up or down to match the IBU contributions? Or do you stick with the dry weight of the hops?
 
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I wouldn't worry about the real late additions, but your IBU's are going to be a bit higher due to the 15 minute contribution using 7.1% versus 5.5%.

Many people will use AAU rather than IBU calculations to compensate (easier math)

AAU = AA% x weight(oz)

So, your one oz of 5.5% will contribute 5.5 AAU. Meaning you'll only need .77oz of the 7.1% for the same 5.5 AAU.

But I rarely bother with this unless I'm really trying to replicate a previous beer or if the bitterkng addition AA% are vastly different.
 

chickypad

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I only ever mess with the bittering addition to match the IBU's of the recipe and leave other additions as written or as previously brewed. I don't know if it's the "proper" way, but it makes sense to me to keep the character of the beer the same.
 
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