IBU not coming out right in recipe, please advise

I just put together this recipe at brewers wherehouse, according to the article i got the recipe from this should be 75 IBU's, but brewers wherehouse is only coming out with 33 IBU's. This is the old rasputin clone in the best of brew 250 recipes issue, if anyone sees what im doing wrong please fill me in, thanks!

http://www.brewmasterswarehouse.com/recipe/f84783cb/wilsons-brew-department-old-rasputin-clone

is the aa the same or close?

What IBU calculation formula are you using? What formula is the article using?

Shooter said:

What IBU calculation formula are you using? What formula is the article using?

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That unfortunetly i have no idea,(dont quite have a grasp on the hops yet) all i did was enter the correct amount of each hop from the recipe into the website, and its coming up differently,

Hmm, well, you do also need to pay attention to the alpha acid of the hop, as mentioned above. They aren't the same from year to year. So, you will have to adjust. This is more important for the longer boil/bittering additions.

I just popped open your recipe on BrewBuilder...are you sure your hop additions are correct? You have low AA for 60min boil, and higher AA for flavor and aroma additions.

Naked_Eskimo said:

I just popped open your recipe on BrewBuilder...are you sure your hop additions are correct? You have low AA for 60min boil, and higher AA for flavor and aroma additions.

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Here is exactly what the recipe says

21.5 AAU cluster Hops
(60 mins)
(3.1 oz/87g of 7% alpha acid)

8.0 AAU Northern Brewer Hops
(2 mins)
(.88 oz/25 g of 9% alpha acid)

8.9 AAU Centennial Hops
(2 mins)
(.74 oz/21g of 12% alpha acid)

Says should finish at 75 IBU's

First item, your alpha acids in the recipe do not match the alpha on the hops you are purchasing. For example, the recipe says 3.1oz/87g of 7% cluster. The cluster you are purchasing is only a 5% alpha hop. You need to up your amount. This is particularly important for the 60 minute addition, as it's going to make the largest contribution to final IBU. The other hops you are purchasing are also different alpha levels than what is listed in the recipe.

EDIT: It appears BMW is using Tinseth to calculate the IBU number, at least according to an old post on this.

try this
4.3 oz cluster
0.81 oz nb
1.3 oz centennial
I think I did the math right?
your recipe calls for 21.5 aau from the cluster
the bmw cluster are 5% aa
aau/aa=oz's
21.5/5=4.3

dzlater said:

try this
4.3 oz cluster
0.81 oz nb
1.3 oz centennial
I think I did the math right?
your recipe calls for 21.5 aau from the cluster
the bmw cluster are 5% aa
aau/aa=oz's
21.5/5=4.3

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Thank you, i applied those changes and it is better, but now listed as 46.5 IBU's, so still short?

Well, it's hard to know how they were calculating the IBU levels in the article, but both BMW and BrewPal software give an IBU level WAY lower than 75 for this recipe.

Shooter said:

Well, it's hard to know how they were calculating the IBU levels in the article, but both BMW and BrewPal software give an IBU level WAY lower than 75 for this recipe.

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When i looked up old rasputin on north coast's website, it claims to be 75 IBU's as well

Wilsons said:

When i looked up old rasputin on north coast's website, it claims to be 75 IBU's as well

Click to expand...

Argh, I was going to input this into Brew Alchemy last night and forgot!!!

I haven't tried punching this into my software but is everyone taking into account the late extract addition? lower gravity wort will give you better hop utilization.