The research I was referring to was related to big breweries, Miller I believe did most of the research, who had abandoned any whole or pellet hops for extracts and "advanced" products exclusively. They found that products providing alpha and oils only were lacking something critical, particularly in "kettle hop" flavor and aroma, which DeClerck had already identified as an important characteristic. (For that matter Wahl and Henius report on lupulin preparations and hop extracts being used at the turn of the 20th century, and note that these should only replace a portion of the total hop bill or flavor and aroma will suffer.) Glycosides were one element identified, but I'd expect there are lots of compounds in the vegetable matter that contribute to "hoppiness," and not just in the kettle. And the research showed that yeast plays a significant part. Craft and home brewers are using some form of "whole" hops in some part of their process, so this is less problematic. But I think we should remember, when excitedly seeking new products to "increase aroma without adding vegetable matter," or get better bitterness that the veggie stuff is in fact part of the equation in flavor, aroma and even bitterness. As homebrewers, we've historically been focused on two things, % alpha (and CoH and beta maybe) and oil content. But we've probably all learned from experience that oil content, for example, doesn't necessarily equate to value in dry hopping. Try a "noble" or old-school English variety, for instance. Beer's complicated, there's more going on than we first expect, I guess is the bottom line. And if my starting point was that I think pellets overdo some things, that doesn't mean they aren't needed in proper proportion.
