I brew a lot of hoppy beers. Most my beers call for 8-14 oz of hops per 5 gallons of beer. Given that the flavor of these beers is dominated by hops, the particular blend of hops used is paramount. I think it's generally agreed upon that—while single-hop IPAs are interesting and can be quite tasty—almost all the best IPAs contain a blend of hop varieties. But what is the best strategy for selecting varieties to pair, and what proportions should one use?
Looking at the hops used in some of the most acclaimed IPAs, some patterns do emerge. IPAs created more than 10 years ago generally use a blend of so-called 'C' hops: Cascade, Centennial, Chinook, and Columbus (Nugget gets an honorable mention here). IPAs from the past 10 years have many new varieties of hops to work with. In these IPAs, Simcoe and Amarillo are frequently paired: as in Alpine's Duet, Ballast Point's Sculpin, Ithaca's Flower Power, Russian River's Pliny the Elder and Pliny the Younger, and Surly's Furious.
With more hop varieties being released every year, hop blending has become increasingly complicated. Given this complexity, I decided to begin my experimentation with just a few hop varieties. But even then I ran into difficulty.
To be specific, I had a recipe for a heavily-hopped amber that I was quite fond of. It contained Nugget and Cascade as flavoring hops, and Simcoe and Amarillo as dry hops. I brewed a lot of this beer, quickly ran through my hop reserves, and had to order another pound of Amarillo. When I brewed the same recipe with the new Amarillo, the beer was starkly different. The beautiful passionfruit aroma had taken on a harsh tinge of garlic. This aroma was evident in the smell of the raw Amarillo hops themselves.
High quality hops are not a commodity. I have found a significant degree of variation in the aromatic characteristics of the hops I have received. Which meant that my quest for an ideal blend of hops was doomed from the start. This realization discouraged me for quite a while, but I have found hope in a new approach to hop blending.
Instead of designing recipes based on the characteristics that particular hop varieties are supposed to have, I brew based on what the current batch of hops I'm using actually smell like. Is this batch of Columbus particularly aromatic? If so, I may use it as a dry hop. If not, I'll use it as a bittering hop. I pay particular attention to the level of sulfuric compounds. At moderate levels, these compounds can provide a pleasant fruity pungency (grapefruit, blackberry, passionfruit), but at higher levels they conjure garlic and cat piss. In general, newer hop varieties (especially Amarillo, Mosaic, Simcoe, Summit, and Citra) contain higher levels of sulfur, but there is a great deal of variation even within a single variety. One of my main objectives in blending is to achieve the right level of sulfuric aromatics.
All this talk of aromatic compounds is, I'm sure, an oversimplification. My main point is that, given the level of variation in hop aroma within each hop variety, brewers should pay more attention to what their hops actually smell like, and less attention to what hops a particular recipe calls for.