xcrunner78 said:
If I change the steep time it changes the IBU, but the hop is not boiled, so it should not change the IBU. Boiling the hops, breaks the double bond and flips it from a cis to atrans state, or another words, from aroma to bitter. During the whirlpool, the hop is steeped, not boiled, and should not increased the IBU, in fact should not give an IBU at all. Am I incorrect with that thought?
Somewhat incorrect.
Hop alpha acids are not terribly aromatic, but high density and fermentation (glycolysis) can change them into flavonoids. Cis and Trans isomers are the resulting "stable" forms of alpha acids, with a ratio of about 70% cis compounds after the boil. Trans isomers tend to degrade faster, which is most of the reason that even the hoppiest beers show only about 80 +/- IBU after packaging.
Hop oils are the aromatic part, but there is a correlation between an increased amount of hop oils with increased alpha acid levels. However, hop aromatics are NOT measured by the IBU calculation. To my knowledge, there isn't any formula to calculate aromatics. This remains the realm of brewer art, skill and experience.
Part of the magic of highly hopped beers happens when the 100 IBU threshold is hit during the boil and the brewer is now breaking as many isomers as are created with further additions. Only humulone and cohumulone matter to the brewer because lupulone doesn't isomerize easily and remains at negligible levels throughout the boil process. Of the two remaining, aggressive bitterness is determined by cohumulone levels more than humulone, since the former is perceived as coarser. Tom Shellhammer of Oregon State showed bitterness
perception from cohumulone to be as much as 5x that of humulone isomers.
*aside: in the same panel, Shellhammer showed that even unhopped beer has about 3 IBU from grain tannin. The talk was about trying to find a new way to measure bitterness.
If it does increase the IBU by steeping it longer in the whirlpool, then all of the hops in the trub should be measured out similar and should increase the IBU as well during the whirlpool stage (usually for me of 30 min.).
There's a lot going on in that phase. Isomers
are being created as wort is hot, but at higher levels and longer than 90 minutes, many are destroyed, too. The taste panel noted above stopped testing at about 75 IBU because there was no difference in perception over 50 IBU. AFAIK, all of the IBU formulas work best under 50 IBUs and there isn't any meaningful research going on above that threshold. What we know and practice as brewers is merely empirical.
The most important thing is to remember that hop isomers are hydrophobic. That is, they look for every opportunity to get out of beer. Brewers lose IBUs to trub, in all foaming, to yeast cell walls, fermenter surface area, racking, bottle filling and everywhere else that beer touches a new surface.
So, process has a LOT more to do with what ends up in your glass than any calculation. Thus, I wouldn't sweat the IBU levels above 60. Rather, I'd look to timing those hop additions to give the best flavor and aroma impact for the beer I'm making.
