Photo by Stirling Noyes/Flickr CC
At lunch last weekend I overheard someone at another table say that when she wanted a greater caffeine buzz, she chose a different roast. I can't remember whether she chose darker or lighter roast for the greater buzz, but it doesn't matter; both answers were wrong. The effect of coffee roasting on caffeine content is so negligible as to be immeasurable except under tightly controlled laboratory conditions.
We generally estimate caffeine content to average 1% for coffea Arabica and 2% for Robusta (coffea Canephora) by weight. The real issue is the caffeine content of the cultivar, i.e. the species (Arabica or Robusta) and especially the variety of the coffee within the species. [Curator's note: As Jerry helped teach me for my book, good coffee -- everything Peet's and also Starbucks sells -- is Arabica.]
The word "varietal" is often incorrectly used referring to coffee. "Variety" or "varietal" is an important word to an American wine producer since our tradition is to label wines by varietal, eg. Zinfandel. In France or Italy, the tradition is to label by the appellation where the wine is grown, and most wines are blends. But generally only coffee professionals encounter the variety of coffee; the consumer rarely knows whether she is drinking Catuai (red or yellow), Caturra, Typica, Mundo Novo, SL28, or Kent, to pick six of the more than 3000 named Arabica varieties. [Curator's note: For single origin coffees, what customers see is a name derived from the country of origin like Guatemala Antigua or a specific farm like Guatemala San Sebastian; for blends you'll see a proprietary name, like Peet's Major Dickason's Blend.]