Very cool podcast Denny and Drew. I am absolutely in no way surprised. Calculated IBUs only help when used as a benchmark for a specific brewer trying to duplicate or adjust bitterness on his or her same equipment/recipe/ingredients.
Frankly, a brewer, especially homebrew, would do just as well just using grams of X hop for X time at X temp as their measuring stick. The use of IBU just implies a more precise and predictable outcome when that precision and predictability doesn’t exist. Certainly not when different types of hops are substituted and only %A are considered.
Neither had we! But his explanation makes sense…when he was developing his formula pellets were so bad that people didn’t really use them. Of course, because pellets break down so quickly protein coating isn’t an issue for them as it is with whole hops. I’m in contact with Glenn and we’re talking about experiments to test the protein effect.
Sp glad you enjoyed it, Jim! It was cool to be able to have Glenn on the show. I think his point is well taken…learn what you like and call that YOUR IBU scale!
Frankly, I prefer low, medium low, medium, medium high, high as descriptors of bitterness rather than a number. Of course you need to use the same descriptors of hops flavor and hop aroma.
My biggest take away is that the shape of the curves predicted by Tinseth are correct. The actual predicted IBU may not be correct.
To me that means Tinseth is still very useful. In your brewery, overtime, you learn to correlate what Tinseth predicts with the bitterness you experience and then you can use Tinseth to guide recipe design with respect to bitterness.
Where things get difficult is trying to understand bitterness from brewery to brewery since Tinseth may predict the same number for two breweries but actual bitterness, according to the Igor results, can vary significantly.
I’m over here using the real ibu formula like… Huh!!!..
W= B ∗ V
1000 ∗ A ∗ U
Where W is the total weight of the hops to be used in grams, B is the desired
bitterness in IBUs, V is the final volume of post boil wort in the kettle in liters,
A is the alpha acid content of the hops (4.7% AA means that A = 0.047), and
U is the assumed hop utilization.
For example targeting 16 IBUs and assuming a utilization of 28% (i.e.
set U = 0.28 and B = 16). Utilization will vary from system to system; if your
beer ends up too bitter, try raising the utilization to 30%, and if it ends up
not bitter enough try lowering it to 25%. For example, assuming your post boil
volume is 21 liters, your hops contain 4% alpha acids, and your utilization is
28%, you would use a total of 30 grams of hops.
Because Glenn only used whole hops, there is some debate about whether boil gravity or protein coating causes the reduced utilization. I’ve spoken with him and our lab person to try to devise some experiments to try to get a handle on that. He also stressed that kettle geometry was a large factor.
