Part II: The Basics of Coffee Roasting

Roasting, like we said, is cooking the coffee beans from green to brown. So sling on your apron and march into our cyber-kitchen, as we whip up a mighty-fine batch of coffee learnin’.  

In Part One of the Basics of Coffee Roasting, we urged readers to steer clear of the dark side (and the light side), offering a roasty alternative: profile roasting.

The idea of profile roasting is that each coffee is different, requiring specific roasting parameters to coax out the desired flavors.

In today’s Part Two, we’ll drop in on our chef--er, Roaster and Green Buyer--Winston Harrison, and talk in detail about what’s cooking back there in our kitchen. Or roasting room. You get it.

Two reminders before we start: 1) We are about to talk about SCIENCE, so take 100 deep breaths or call your pastor or take a walk before starting; 2) As always, coffee is a fruit.

Coffee roasting happens in three stages, Drying, Yellowing/Browning and Caramelization/Acid Development.

In Stage One, the still-green coffee beans are added to the pre-heated roasting drum. In its earlier life, this green coffee lie submerged in fermentation tanks--so, although the coffee is dried before shipping, the inside of the bean is still dense with water.

Once the coffee is dried, science truly happens. At this point, the heat of the roaster begins to cook, or enhance, the coffee’s natural sugars (like sucrose). This is the crux of this first stage: developing sugars (sucrose being the main one).

As the coffee continues to warm, the water inside the bean turns to gas (as you’ll remember from tenth-grade chemistry).

This leads us to Stage Two.

At this point, all that water that saturated the coffee has turned to so much gas. And all that gas has to go somewhere. In this stage, the coffee turns yellow, then brown. It grows significantly in size, with the rumbling gases inside building pressure on the coffee’s cell walls.

Finally, in Stage Three this water-turned-vapor explodes out of the bean--what’s called “first crack.” If you were within earshot, you might think we were running a small-batch Orville Redenbacher operation--”first crack” sounds a lot like popcorn in the microwave.

IDEA: Microwave coffee roasting! Wait, nevermind--forget we said that. Back to Stage Two.

After first crack, the coffee’s inherent sugars and acids hit the dance floor. It’s a delicate dance between the two, and, without an attentive roaster, could end up like a sweaty-palmed junior high slow dance. We’re shooting for something along the lines of Footloose.

When the dance begins, those coffee-sugars that were being enhanced earlier have now begun to caramelize. Too, the acid that was native to the coffee since its fruity beginnings has now begun to develop. The dance, at this point, is being performed by the roaster, Winston (so much dancing): he must strike the perfect balance between sugar and acidity.     

Caramelize the sugars too much and caramel will be the last note you taste--the coffee will taste burnt. Don’t rein in the acidity and the coffee will be sour and acrid. This is the worst case, sweaty-palmed dance scenario we were talking about. We don’t want sweaty palms anywhere near our coffee.

Winston only finds the right balance by exhaustively charting the roasting process and manipulating each section of the roast to enhance the best qualities of the each coffee. The right balance--the beautiful interplay of acids and sugars--will dance on your tongue, the bright cleanliness of acidity twirling in the arms of a round, sugary sweetness.

That’s the goal: a perfectly-executed balance between sugar and acid. A Dancing With the Stars-winning balance (or, if you’re not into that, perhaps a roasting competition-winning balance?). When that balance is nailed, the roast is finished.

Attentive readers will note that we never entered a Fourth Stage of the roasting process. That’s because the Fourth Stage is not good. The Fourth Stage is called “second crack,” when there’s a carbon dioxide explosion in the coffee. If the roast lasts to this stage, the sugars have been caramelized to a crisp. This would be the equivalent of you, sweaty and heaving, staying on the dance floor at your cousin’s wedding long past when the band packed up and went home.

Don’t stay on the dance floor that long, and don’t let your coffee do that either.