Finally, and to me, most confusingly, those Steiner researchers described the humulinone bitterness as smoother. “ The bitterness profile of the humulinone beer, however, appeared smoother, and there was less lingering on the tongue than with the iso-alpha acid beer. This smooth bitterness makes sense given humulinones are more polar than iso-alpha acids and should therefore not stick or linger on the tongue as long as iso-alpha acids.”

Wait, smoother? Either they don't taste smoother to me, or there's another cause. Well, there are other causes. Again, when we're dealing with such extravagant amounts of hopping, even tiny contributors may play a noticeable role. Which ones? "Polyphenols as well to some degree," Shellhammer noted. Polyphenols are a bit like tannins, and by Tom's description, these seem more likely to be the cause of the objectionable bitterness I taste. "Like when you make tea at home, you can get bitterness from that. When they're really small they can taste a bit more astringent."

Another possibility is beta acids, another constituent of hop oil. They seem important--though to my knowledge unexplored. Just as oxidized alpha acids become humulinones, oxidized beta acids become transformed as well--into hulupones. Again, our friend Tom Shellhammer elaborates at Beer and Brewing Magazine.

However, hulupones are bitter and can contribute substantially to the final flavor of beer. Anecdotal claims suggest that hulupones have an unpleasant bitterness quality. Hulupones are relatively stable once formed and can survive all stages of the brewing process. They can be formed via the oxidative degradation of hops during storage. As hops oxidize, the bitterness that comes from iso-alpha acids diminishes because their precursors, alpha acids, are lost as a result of oxidation, but this is somewhat offset by the presence of bitterness from the hulupones.

There are a couple other things I'll throw into the mix. First, all of this illustrates that chemical interactions are moving variables around, so we need to be wary of fixed points. What else is moving the dials? We know for sure that yeast creates "biotransformation" of hop flavors; what else is it doing? Another question I keep coming back to has to do with human hardware. We know we don't all get the same flavors from hops; you may get lemon or dill from Sorachi Ace, white wine or human sweat from Nelson Sauvin. When someone tastes humulinone bitterness and gets a "smoother" quality, is that a universal experience, or will each person get different levels of smoothness?

In our exchange, Stan added glycosides as another factor that might affect bitterness. Of course, hop variety, dry-hop method, and any number of other untested variables may well be at play. And these are the known-knowns. What else may be happening that we haven't discovered yet?

What we're left with, at this moment, is a fascinating stack of questions to which answers will be very slow in coming. The one answer we can definitively provide is this: that old myth that dry-hopping doesn't add bitterness is not strictly true. In high enough volumes, dry hopping is a significant source of bitterness. (Forget those "zero IBU IPAs.") What the precise sources of that bitterness are and how breweries can control it remain very open questions. Going back to that glass of Great Notion Juice Jr. I was drinking, I have a few possible suspects that might account for the harsh bitterness I tasted (including user hardware), but no convictions. And it will almost certainly be awhile. I am, however, looking forward to the field work.