Skimming through "Hops" by Stan H. He mentions that 50% of alpha acids are lost in the brew house and 20% is lost in fermentation and packaging. Is anyone out there planning recipes to these numbers? ie - to make a 30 IBU beer - add 100 IBUs? As an example, it is noted how a batch of HopHenge had 243 calculated IBUs, 117 measured in the fermenter, and 87 measured after packaging. I haven't seen many talk about this. What are your experiences? And - related - anyone know of any such percentages for essential oil loss, ie flavor and aroma?
Solubility limit, pH, yeast strain all factor into this. More flocculant yeasts are said to remove more of the Iso-AA. Maybe that is one reason Chico is so popular in AIPA. This says a little about it. http://appellationbeer.com/blog/how-many-ibu-about-one-hundred/
Personally, I haven't really been calculating for any of these factors. If I were to attempt to suddenly do so, I am afraid I'd be way off on the high side. I thought my beers were coming out in the generally expected range, but perhaps my numbers don't reflect reality. However, if my numbers are WAY off, then my pallet my be WAY WAY off. But then there's the ol' adage "if it ain't broke, don't fix it." [/unhelpful post]
Our palates have been calibrated to the IBU calculations we've been using for years. If the calculation says 50, then I've got a pretty good idea what to expect. If adjusting for AA loss gives me, say, 20, I don't care. It tastes like what I expect 50 to taste like. And if I adjust the hop schedule to account for the AA loss (and actually give me 50), it's going to be too bitter.
I noticed that my beers were not as bitter as they should have been for my hoppier beers so I have factored in that my beers are going to be around 85% of calculated IBUs. I set my IBU calculations on my spread sheet to calculate and multiply by .85. I use this as my IBUs, still a little low.
I was confused by the bitterness when I started brewing. A 50 IBU homebrew seemed to taste less bitter than a similar commercial beer that was advertised as 50 IBU (I was using clone recipes as a guide). I later realized that my problem was that I tended to bump the gravity a bit from the recipe, resulting in a lower perceived bitterness. A 50 IBU 1.060 beer seem less bitter than the same beer at 1.050. Once I figured that out, life was good (though, it was pretty good before that, too). But the bottom line remains intact - I use the IBU calculation as an indicator, not as an absolute measure of IBUs. I don't care that it's not accurate, only that it's consistent.
In my opinion, Mike hit on the real issue which is perceived bitterness. There is an interesting online article entitled “How Do We Measure The Bitterness of Beer” (see link below). In that article the author stated: “There's actually much more to the IBU story, especially when it comes to human perception of bitterness. But that's a discussion beyond lab-measured IBUs and their use at places like Victory. I'll get into the human perception of bitterness and its complexities when paired with beer in the forthcoming column.” I have anxiously been awaiting the author’s follow up article. Does anybody have any good scientific papers on perceived bitterness of beer? Cheers! http://www.popsci.com/science/article/2013-04/beersci-ibus-explained
Here's my other example. I've plugged in the Pliny recipe VC has published. The calculated IBUs from this recipe is 175.5 IBUs. The actual IBUs in the article is 90-95 IBUs, or about 50% of the calculated value. I've personally never built a recipe accounting for this. Maybe it really applies more for a double IPA. And you guys are right - if it tastes good, then why mess around. But - it makes me think if my calculated 90 IBU IPA isn't quite as bitter as I'm expecting, this is the reason why - and maybe I should be planning on adding 150 IBUs to get the bitterness I'm looking for...? With regards to perception - I think this would become clear if you attempted to clone a commercial IPA that advertises the measured IBUs - and designed the recipe to match the advertised IBUs on a calculation basis. The two should be noticably different in terms of "perceived bitterness". As an example - the Pliny clone would include 1.25 oz of Columbus at 90 mins instead of 3.5 oz as is indicated. I can't imagine these beers, side-by-side, would taste the same. Anyone out there ever try anything like this?
