Non-stick pan? Stovetop? You probably have everything you need to start experimenting with green (coffee) beans.
Admittedly, I get hung up on semantics, but I think toasting works better than roasting to describe coffee's transformation from green, farm-raised innocent to bronzed, sophisticated bean of the world we know and love. Roasting basically means to cook in an oven, while toasting expressly means to brown—like how coffee beans turn brown under increased temperature—whether in an oven, with proximity to fire, or through some other kind of radiant heating.
Indeed, caffe tostato is the Italian term for roasted coffee. Okay, it's out of my system. The toasted campaign ends here.
All the necessary equipment for effective coffee roasting resides in even the most Spartan of kitchens. Non-stick pan? Stovetop? Get ready to roast.
Today's topic is home roasting, with an "R"—a kind of precursor companion to the home blending discussion last time. Like blending, exploring roasting can inspire you to take your coffee craftsmanship further, and create deeper understanding of coffee's fundamentals. "Try this at home," with benefits.
[Corby's note: And with caveats! In my Joy of Coffee, I was and remain leery of home roasting, for reasons I'll put in a note below. But Giorgio's notes are explicit, helpful, and might even convince me to change my mind.]
At first glance, the idea and process of roasting coffee seems simple: apply a certain amount of heat to raw beans for a set amount of time. That's how, over an open fire, westward-pushing pioneers got their coffee ready to brew throughout the 19th century, as did many coffee-consuming American households into the early 20th century. Home roasting as a necessity effectively ended with the advent of high-volume roasters like Hills Brothers and Boyds in the early 1900s. The enterprising Arbuckle Brothers of Pittsburgh had patented a coffee roasting process as early as 1865.
As with so many processes, control and precision get in the way of ease in roasting coffee beans. Maintaining proper heat for the right amount of time is only step one. Cooling--the more nuanced, critical final phase—is where things can get tricky. Remember that food continues to cook when removed from heat. Just-roasted coffee beans are no different.
From a purely functional standpoint, roasting times can range from only a few minutes to many more. As intuition suggests, higher temperatures mean shorter roast times. For me, both ends of the spectrum produce subpar results: avoid slow and low, just as you would fast and hot.
Fast roasting, also called high-yield, rapidly cooks the outside of the bean, leaving the core almost raw. No matter how high the heat, the short roasting time cannot develop the beans' full range of aromatic components and evaporate the naturally occurring moisture. Residual moisture accelerates the staling process, prematurely exposing coffee's less pleasant aromas and flavors. What's more, fast roasting leaves too much chlorogenic acid in the bean, carrying unpleasant, astringent sour notes into the cup.
Slow roasting at relatively low temperatures fully develops a bean's aromatic components, but then literally (cruelly!) takes many of them away during the prolonged application of heat. You'll detect pleasant toasted bread notes, but also a bracing bitterness and, generally speaking, flat flavors. The result is the same, no matter the type or quality of unroasted coffee you start with.
When it comes to roasting coffee, the middle road is the road best traveled. Professional roasters generally prefer a process involving a rotary drum, in which a gas burner creates radiant heat surrounding the coffee. Time and temperature pairings will vary by roasting company, but a benchmark combination of, say, 12 minutes of roast time and a final temperature of 420 degrees F should allow for full aromatic development and nearly complete water evaporation. A few seconds or degrees in either direction can make a huge difference, because the transformation occurring within the beans increases in force and speed toward the end of the process.
Budding home roasters will be hard pressed to get the consistent results produced by sophisticated, industrial (and expensive) drum-based systems, but there's good news. All the necessary equipment for effective coffee roasting resides in even the most Spartan of kitchens. Non-stick pan? Stovetop? Get ready to roast.
Set the pan on a medium flame and add just enough unroasted beans to cover the bottom. Cover fully with a lid—ideally a clear one, so you can see color changes without removing the cover and lowering temperature at a crucial moment. Vigilance is critical: don't just set it and forget it. To ensure even roasting, keep the coffee moving by gently, continuously shaking the pan.