IBU Help

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daveooph131

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What is the difference between AAU and IBU. I am familiar with calculating AAU, but am unsure as to what I really need to know about IBU. Thanks.
 

Sigthor

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IBU is the international bittering units. It is just a way to signify how bitter the end product is. It is determined by the AAU's of the hops used, their boiling times, and the efficiency of extracting the alpha acids. From what I understand you can calculate about what they are, but it takes lab work to get the exact IBU's.

I know there is a formula for calculating an estimation, but i'm not sure what it is.
 

SumnerH

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IBU is the international bittering units. It is just a way to signify how bitter the end product is. It is determined by the AAU's of the hops used, their boiling times, and the efficiency of extracting the alpha acids. From what I understand you can calculate about what they are, but it takes lab work to get the exact IBU's.

I know there is a formula for calculating an estimation, but i'm not sure what it is.
There are many formulas. None are accurate in all cases, but several (e.g. Tinseth, Rager, Mosher) are pretty close in a lot of cases. Wheat/rye beers and beers with simple sugars added are cases where they get less accurate, as are really wacky hopping schedules (if you're doing a 60-90 minute boil and your additions are at 60/45/30/15/5 minutes or some subset of that, they're likely pretty accurate).

But they're limited in how accurate they can be; the same recipe brewed by several people will show actual IBU variations of more than 20%.

If you're just trying to calculate IBUs in one of your recipes, use a piece of brew software (The Beer Recipator - Home is an online tool that's free and easy to use--click "spreadsheet" and enter your recipe. https://www.homebrewtalk.com/f84/software-available-42935/ has links to other available software, both commercial and free).

If you want more info on how the formulas work and the issues involved, see my thread over here:

https://www.homebrewtalk.com/f128/estimating-bitterness-algorithms-state-art-109681/
 

BigEd

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What is the difference between AAU and IBU. I am familiar with calculating AAU, but am unsure as to what I really need to know about IBU. Thanks.
AAU are simply the AA% of a hop multiplied by the quantity in ounces. So two ounces of 5%AA hops = 10 AAU. IBU is the amount of bitterness in a beer, a factor of the quantity and strength of the hops and how much of the potential AAU has actually dissolved in the wort during boiling. IBUs are a much more accurate way to predict and describe hop bitterness in a beer. The easiest thing to do is run your recipe through a brewing software program. Promash, Beersmith and BeerTools are all pretty well known. There are also a bunch of calculators available on various club and brewing websites. :mug:
 
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