« on: March 23, 2016, 02:57:00 PM »
How many actually calculate their actual current AA but looking up the drop off rate and figuring out the current AA by time and storage temp? Probably almost 0% of us.
I did this a few times and then gave up because (a) the various online calculators give wildly different figures, and (b) the creators of the recipes I was using presumably didn't bother making the adjustment at their end, so it was pointless me doing it.
I do wonder how accurate IBU levels could possibly be if alpha acids decline in storage as fast as people say. Getting the right bitterness consistently might actually be impossible for homebrewers. Hopefully someone will tell me otherwise.
For years I have assumed losses for alpha acids based on a swag, not using calculators but attempting to allow for a little common sense based on my own experience. In real life experience, it seems to me that perception of bitterness is not nearly as bad as any calculators put out. If for example I have hops that started at 6.0% alpha acid, and I stored them in my refrigerator for 12 months, and a calculator says there should be a loss of 50% of the original so that it would go down to 3.0% alpha acid remaining, I know from experience that if I assume the 3.0% that a calculator provides, my beer will turn out WAY too bitter. If I instead swag that "meh... maybe it goes down to 5.0% after a year", I have gotten more accurate results, but even in those cases, more often then not, the beer still turns out a little too bitter. So, either alpha acid is way more stable then people tell us, or else the beta acid takes over at some point and offsets part of the alpha loss. For some reason I thought I read someplace that as beta acids age, they develop compounds that are MORE bitter instead of less bitter like alpha acids do. So there might in fact be some sort of balancing act going on. I can't recall where I picked that up, I'm sure it will be Googled by somebody else. But anyway, my point........
It's probably impossible to actually use any calculators to try to determine loss of perceived bitterness of hops due to age. Way too many variables. You can swag it if you like, but my experience says that the perceived bitterness probably only changes by a maximum of about 0.5% alpha acid equivalent per 12 months, somewhere in that ballpark anyway. It's not as bad as anyone without experience will tell you, I do know that.