IBU calculation for blended worts / braggott

community!

I recently found that my calculations of IBUs are not always accurate... Especially when I was making a Braggot. Maybe someone can help me out with the formula or something?

I made a 5 gallon batch of IPA braggot.

I boiled 2.5 gallons of extract with a extract method (3lbs of extract, 12oz stepping grains, Hops at 60, 30, 15 and 1 mins).

At the end I blended it with a 2.5 gallons of mead must making total 5 gallons with OG=1.072. Not bad for an IPA. However, I'm not sure if it will be bitter enough...

So, here's a two batches:

1.   V = 2.5g,  OG = 1.048,  IBU = 158.
2.   V = 2.5g,  OG = 1.101,  IBU = 0.
-------------------------------------------
1+2. V = 5g,    OG = 1.072,  IBU = ?

What would the IBU be?

PS. Fermentation was complete yesterday at 1.014. I will dry-hop it with 3 oz of something citrusy and floral.

Thanks.

Topic extract-brewing partial-boil ibu homebrew

Category Mac

1
answered at

The alpha acids that give the bitterness from hops reach saturation somewhere around 90 IBUs. Since your hops were not exposed to the whole volume of beer (presumably they were filtered out at the of the boil) you aren't getting the full impact from them. It is reasonable to say that the IPA is actually 90 IBUs (saturation is around 90mg/L). Then divide by two for the addition of unhopped mead, leaving 45.

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