dirtybear7

Recipes 

I'm using two different applications for recipe creation, Hopville.com and Beer Tools (only one that works native on Macs). I get to wildly different IBU amounts from each. Which is correct?

I'm making Northern Brewers Belgium Strong Golden Ale extract recipe with some changes to hop amounts and boil time (because of Hopville.com calculator). Here is what I did:

2 gl boil and added the rest in the carboy to equal 5 gl
3 oz 3.9% Saaz 90 min
1 oz 3.2% Saaz 1 min
The O.G. was around 1.078

Hopville.com IBU 27.1
Beer Tools IBU 44.3

Which is correct? Are they using different formulas?

Recluse

Recipes 

My GUESS is that Beer Tools isn't correcting for the utilization factor decreasing considerably due to the high gravity of the boil. The Tasty Brew Bitterness Calculator:

http://www.tastybrew.com/calculators/bitterness.html

which uses the Tinseth equations. (Note that you get DIFFERENT IBU's from the TastyBrew Bitterness calc than the IBU calc in the TastyBrew complete Recipe calculator) gives even less, 11.9 IBU

I built a spreadsheet with the TInseth equation and it tracks very well with the TastyBrew bitterness calc. Of course, there is much difference of opinion as to WHICH calculation (Tinseth, Rager, etc..) is really 'correct'. You kind of have to stick with one so at least you get to know what the number MEANS in your own brews whether or not it is experimentally verifiable.

The gravity of your boil is very high leading to low hop utilization. On the other hand, a 90 min boil with 3 oz of Hops, even at the relatively low AA will really bring out the bittering!

jkarp

Recipes 

Wort gravity has no direct influence on hop utilization. All the IBU formulas are gross over-simplifications of what actually happens in the kettle, but Tinseth is arguably better.

Recluse is definitely right however when he said "You kind of have to stick with one so at least you get to know what the number MEANS in your own brews whether or not it is experimentally verifiable." Pick a formula and don't worry about the actual number.

dirtybear7

Recipes 

Thanks for the help all! I noticed hopville.com allows you to choose between Tinseth, Rager, Hopville, Garetz, Average (hopefully average of all the other calculations). Is Tinseth the most popular? Did I severely over hop for the style?

Recluse

Recipes 

I don't think you over-hopped, but only a taste of the finished product can tell for sure! The pure Tinseth calc would say you might have UNDERHOPPED, but as always, YMMV and all that matters is how it actually tastes.

Here is some reading/listening material if you want to be totally confused...er.. that is INFORMED

http://www.realbeer.com/hops/FAQ.html
http://www.realbeer.com/hops/research.html
http://www.basicbrewing.com/radio/mp3/bbr01-05-06.mp3

Sometimes too much theory is less useful than a little practice..but I kind of geek out over this stuff.