IBU Calculation

[Calum]

I am writing my own brew spreadsheet but I am stuck with the IBU calculation on hops added at the end.

I know the calculation for the hops added at the start of the boil is:

IBU=( (%AA x Amount in grams x 2) / Brew Length in litres)

However, how much bitterness does the addition of the aroma hops add (is there a percentage extraction based on the time in the boil)?.

Does anyone know off hand or know of a site where it is demostrated?

[bitter_dave]

Ray Daniels gives a basic utilisation table (p. 80), although he assumes a higher utilisation at 90 mins (27%) than the equation you give (20%). Anyway, this is the utilisation chart for whole hops (in mins):

Dry hop 0%
0-9 mins 5%
10 - 19 12%
20 - 29 15%
30 - 44 19%
45 - 59 22%
60 - 74 24%
75 + 27%

This is approximate, but you might find it useful

[Calum]

Thanks chaps for the swift response.

Ray Daniels gives a basic utilisation table (p. 80), although he assumes a higher utilisation at 90 mins (27%) than the equation you give (20%). Anyway, this is the utilisation chart for whole hops (in mins):

Dry hop 0%
0-9 mins 5%
10 - 19 12%
20 - 29 15%
30 - 44 19%
45 - 59 22%
60 - 74 24%
75 + 27%

I used the calculation from Graham Wheelers book but I will adjust the calculation with the details above and see where it leads me.

I'm brewing tomorrow so will hopefully have a new spreadsheet to plug all the details in.

[Jim]

Here's some good info from the Brupacks site. They give the formula for calculation bitterness plus some general info on using hops. Recommended reading!

[mr bond]

great calculator on this site

http://www.grumpys.com.au/calculators.php3