Originally Posted by jbsengineer
Understand. So in your opinion where in the boil would you rely on the amount versus the IBU's? 15 minutes there is some bitterness added so you could use the IBU calculations to mirror the amount of hops. Whereas at 5 minutes there are so little IBU's you probably want to rely more on the amount of hops proportional to the batch size?
No, I'd probably use the same amount of hops at 15 minutes as in the recipe I'm following, regardless of the AAUs.
Think of it this way- flavor and aroma hops are like spices in cooking. If you use, say, a teaspoon of oregano in your spaghetti sauce, using .75 teaspoon will lessen the flavor. It'll still be ok, but not with the same flavor punch as intended. The same is true of hops in those late additions.
I'm not sure how many IBUs a small AAU difference will be in 15 minutes without running it through some software- but it won't be much. The difference between 5.7% AAUs and 6.5% AAUs in a 15 minute addition should be negligible.