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April 2009

Steve Kirbach, head roaster at Stumptown Coffee, reminds me of a fireman on an old steam locomotive as he tends the valves, temperature gauges, timer and the fire under the spinning drum of the 15-kilo Probat roasting machine in the Stumptown on Southeast Division Street. He talks about guiding the beans’ “travel” on their noisy 13-minute journey from their starting point as blue-green seeds (still alive enough to germinate) to their final stop as dark, aromatic pellets with the flavor and texture profile he’s trying to deliver to Stumptown: orange, toffee and chocolate flavors with balanced sweetness, acidity and body.

I’m thinking about my own experience with these flavors in macchiatos: toffee, yes; chocolate, yes; orange? I’m not sure about that one, and as I begin to wonder about these deficiencies of my palate, Jim Kelso, Stumptown’s head of quality control, brings over a cup of lightly roasted Ethiopian Wondo to sample. It’s light, floral, almost tea-like, with none of the assertive, roasty, macho macchiato-bravado that I’m used to. And it has surprising flavors I’ve never noticed in a macchiato. One of them is a definite grapefruity note – close enough to orange for me to pass the cup to Steve and ask him if he can detect the same thing I do. He sips and nods his head: “definitely citrusy.”

Beans destined for espresso travel farther, and darker, in the roaster that coffee meant for brewing in hot water. Flavor qualities particular to the bean are more evident in lightly roasted destined for brewed coffee. These begin to fade as the roast gets darker, at which point flavors are more connected roasting begin to dominate.

Think of the flavor transition between raw almonds and roasted ones for some idea of these changes in roasting coffee. Aleco Chigounis, Stumptown’s green coffee buyer, reminds me that “coffee is a fruit. It has the same organic compounds that some fruits have, and that flowers have as well.” Professional coffee cuppers use fruity words — plum, apricot, citric, malic (a green-apple flavor) – as well as brown sugar and caramel to describe brewed coffee flavors. For the roastier beans meant for espresso, besides toffee and chocolate, there are spice flavors: clove, allspice, cinnamon.

If your barista is having difficulty adjusting sour or bitter from a batch of beans, the problem could be coming from basic issues in the roast: under-roasting (hence underdevelopment of sugars from the bean’s starches) will produce an unlikable sourness that’s hard for the barista to overcome. Bitterness, an otherwise great asset to a balanced espresso drink, can be overdone in the bean by over-roasting. Too much roasting over-carbonizes the bean’s sugars and produces a number of other harsh bitter compounds in the very complex cascade of chemical reactions that go on inside the bean during the roast. One interesting recent bit of food science has dispelled the old idea that bitterness in coffee comes from caffeine. Caffeine is bitter, but it’s not concentrated enough in coffee to taste.