Same recipe different IBU's?

[Johns brew haha]

I have built a recipe where everything was the same but in the new recipe my IBU's were totally different. One recipe I have 1.5 Hallertau Blanc pellets at boil for 30 min which gave me a 19.49 IBU reading. then on other recipe I did same thing but on that one it shows me 16.32 IBU's, with the exact same recipe, how can this be?

I can share to public if that will help, right now they are private.

John

 

[Nosybear]

Would help if you were to share.... There are three factors that determine IBUs, one is time, one is sugar concentration and the other is the %AA in the hops. Up to a certain point, more time boiling means more IBUs, higher sugar concentration means lower IBUs and higher %AA means higher IBUs. Without sharing, no way to know which of the factors changed. My hypothesis is the second recipe had a higher original gravity than the first, reducing hop utilization, resulting in a lower IBU value.

 

[Johns brew haha]

https://www.brewersfriend.com/homebrew/recipe/view/585451/belgian-strong-ale-003
https://www.brewersfriend.com/homebrew/recipe/view/572925/belgian-strong-ale-002

 

[Nosybear]

Check the amounts of hops you put in. In one recipe you put 1.5 ounces of hallertau blanc, in the second 1.0 ounces. That's the fourth variable, the amount of hops you add.... It's the 15 minute additions that are different, by the way.

 

[Johns brew haha]

correct, as recipe has boil hops at 1.5 oz in each and the boil hops has a different IBU.

 

[Johns brew haha]

thats what I am talking about. My 1.5 oz hops with 15 minute boil time or even 30 min boil time they are different on same recipe, so why are they different , I am not seing it?

 

[Hawkbox]

Uh... you have 2oz in one recipe and 1.5oz in the other recipe for the 30 minute boil.

 

[J A]

Maybe you edited these recipes but none of the hop amounts are the same. Not sure what your question or objective is at this point.

 

[Johns brew haha]

ok I placed both recipes back to the same settings. Now take a look at the Boil Hops IBU, on recipe 002 it's higher than on recipe 003, why is that I can not tell.

 

[J A]

On 002 you have a "no chill" extended boil time set to 15 minutes - it's in the "more" section on the lower right of that section.That's what's giving you different hop utilization. When you reset that to zero, it makes both recipes the same.

 

[Johns brew haha]

that was it, thanks so much.