I've pointed it out before too, but hop storage/age, etc. all affect actual AAUs, and what is listed on the package is probably not correct by the time you actually get your hands on the hops and use them, unless you know that they stayed in the freezer from manufacture, to distribution, to your own freezer. Hopunion and other places list storage / degradation over time #'s for each hop. They are different for each kind of hop, some stay more stable then others. But you have to know hop storage conditions from beginning to end and the actual age of the hops to really even use them to accurately figure things out.ScrewyBrewer wrote:For a price there are IBU testing companies out there who will analyze your beer sample and send you a full report. It would be fun project for a club or group of brewers to split the cost, cast a vote for the number of IBUs and see who comes closer. Having worked with a number of hop utilization formulas over the years myself my favorite saying when estimating IBUs is from John Palmer.
"Utilization numbers are really an approximation. Each brew is unique; the variables for individual conditions, i.e. vigor of the boil, wort chemistry, or for losses during fermentation, are just too hard to get a handle on from the meager amount of published data available. Then why do we bother, you ask? Because if we are all working from the same model and using roughly the same numbers, then we will all be in the same ballpark and can compare our beers without too much error. Plus, when the actual IBUs are measured in the lab, these models are shown to be pretty close." ~John Palmer (How To Brew)
Luckily most people can't even detect anything less then a 7 or so IBU difference, so often it doesn't matter in the end.
A lab can, but does it ultimately really matter if your mouth can't?
"Ballpark" as said above in the quote is really the best way to describe what we do.
