There's been a lot of industry talk these past few years over Single Origin Espresso. And it's continued with James Hoffman taking the title with the use of two different SO's at the 2007 WBC in Japan. So is espresso being re-defined, or is this something akin to espresso that is merely extracted in the same fashion?
We can beat the nomenclature to death debating whether Single Origin refers to three El Salvadoran beans, El Salvadoran beans from the same region, or one single El Salvadoran bean, consisting of one cultivar, from one farm. Loosely defined, we could say you have a lot of X beans that come from one country of Origin-- El Salvador. These El Salvadoran beans have not been blended with anything, and you don't blend them with anything after receiving them. In other words, we can generally suppose it's self-evident in the description. Unnecessary rambling I'm sure.
Just because I blend a few beans together, roast them, grind them, stuff them in a portafilter, etc, the resulting brew may be espresso, it may be just horrid espresso, or it may not be espresso at all. I'm not of the camp that believes all espresso needs to have a bit of Robusta in it, but I believe there are certain elements an espresso must have. First, it needs to have complexity. There should either be a layering, a blending or a merging of different flavors. Second, there should be recognizable crema that blankets the tongue, gives body to the drink and from which you can gather a nice aroma before drinking -- if you so desire. Lastly, espresso should have persistence of flavor. There should be a pleasant lingering element that stays with you. And to me, whether this is lingering on the tongue, or lingering on your mind because the shot blew you away is ok in my book. It is these same elements that should exist for a bean to cross the Single Origin espresso threshold.
Single Origin espresso should still be about crafting a good espresso, with dynamic and complex flavors, good body, mouthfeel, crema, and a persistence of flavor. These are the things you should look for when examining beans and pulling shots. Ask youself, what is it missing? If the answer is "nothing" then you may have stumbled upon a great Single Origin espresso.
My two beans.