Question on hop additions

[Blancaster]

Hope someone can explain to me how this calculation works
I was listening to a podcast of a Jamils Can You Brew It show
The recipe was based on a 100 Hectoliter system.
My question is on the first edition of hops

The head brewer stated for the for the 90 min addition:

2 lbs Horizon @ 12%AA
2 lbs Summit @ 17.5%AA
I understand that, both of those hops average on the specified AA%
Im confused on the next addition. They are using a hop extract.

2 - 1 lb cans Nugget Extract @ 45%AA
Then they said that would be equivalent to 20lbs @4.5%AA or 10lbs @9%AA
How does that work? how do they convert the 45%AA of a hop extract into 10lbs @ 9%AA?

Thanks for any help given!!

Brandon

[SkyBrew]

I have never brewed with hop oil extract so I have no firsthand experience but here is what I found out about the "hopshot"

Source:
http://www.yakimavalleyhops.com/product ... ot10ml.htm


"The HopShot syringe contains 10 milliliters of extract. One milliliter yields around 10 IBUs in 5 gallons of 1.050 wort when boiled for 60 minutes."

So 1 milliliter yields 10 ibus in a 5 gallon batch.

Volume of extract (mL) = AAU (g) x Density of hop extract (g/mL)

hope that helps

[Blancaster]

I should have typed one line a little different
Then they said that would be equivalent to 20lbs @4.5%AA or 10lbs @9%AA In hop pellet form.

[john mills]

They're just using an IBU calculation. IBU is IBU regardless of the weight of hops used to arrive at that amount of hops used or IBU.
Extracts remove the vegetative component of the bittering. That plant material soaks up wort, decreasing yield of beer after boil. Excessive amounts of plant material add grassy flavors.
You can substitute hops for extract, just like extract for hops.