Posted by Matthew on 9/29/2023 to Coffee Education
Coffee aficionados know that there is no such thing as the perfect cup of coffee. You can get close, but actual perfection is elusive. It also depends on what you’re after: the perfect cup of coffee on a cold and gloomy afternoon might not be what you would brew for a workday morning. Yes, coffee should suit your mood, whether it’s light and bright or earthy and dark. The starting point to the almost-perfect cup, however, is always the same: roasting your beans of choice.
What’s the secret behind the rich and complex flavours that grace our mugs? Well, here’s a crash course on the art of coffee roasting, including the steps involved in transforming green coffee beans into the aromatic elixir we all adore.
Our journey begins with the selection of the finest green coffee beans from a single source, or blended to change the flavour profile. ‘Green’ beans may be green, off-white or tan. Some beans lend themselves to a lighter roast, some a darker one.
Most blended coffees that you buy in the grocery store contain a blend of Robusta and Arabica beans because robusta beans are—you guessed it—more robust, less nuanced, and lend themselves to dark roasting. C2CC only uses Arabica beans because…well, they’re tastier.
Choose your roaster
There are several basic kinds of roaster available. Every roastmaster has their preference of machine, which may change depending on the kind of roasting they’re doing:
- Drum Roasters constitute the original coffee roasting machine. Beans are loaded and heated while they tumble. Traditional drum roasters use open flame to roast, which takes more skill to get right, while more modern versions heat the beans indirectly.
- Centrifugal Roasters are a newer development that employs centrifugal force to evenly distribute and hold the beans in place as the drum rotates. Indirect heat is applied from the outside.
- Fluid Bed Roasters blow hot air through a perforated floor on which the beans dance, ensuring a uniform roast.
The Diedrich IR-12 Drum Roaster
At Coast to Coast Coffee, we have worked with a wide variety of roasters. Our roastmaster, Matthew, founded C2CC on the strength of a personal favourite: the Diedrich IR-12 drum roaster. It has a maximum capacity of 12 kg, so all our green coffee is roasted in small batches. Small batch size, coupled with infrared gas burners that allow us to roast with conductive, convective and radiant heat gives us tight control over the roasting process and the ability to finely-tune the roast profiles of each of the coffees we offer.
Firing & drying
Coffee roasting machines need to achieve precise temperatures. Preheating ensures a stable environment for the beans, allowing for uniform roasting. Once the initial temperature has been achieved, the roaster is charged with relatively flavourless green beans. As the temperature inside the roaster begins to rise, moisture within the beans starts to evaporate. This is a critical step, as it sets the foundation for subsequent flavour development.
Next up is the browning phase, where the beans undergo a series of chemical reactions. Sugars within the beans caramelize, leading to the formation of aromatic compounds. This phase is often marked by a subtle change in the beans' color, shifting from green to a light brown.
One of the defining moments in coffee roasting is the "first crack." It's an audible signal that the beans are undergoing significant changes. The beans expand and crack, releasing pent-up gases. At this point, they've transformed from green and bland to flavourful and aromatic.
Roastmasters, skilled alchemists that they are, closely monitor the beans' progress during the roast development phase. The duration of this phase can dramatically impact the coffee's final flavour. A shorter roast will preserve the bean’s natural characteristics, while a longer roast will produce bolder, smokier notes. For those who prefer darker roasts, there's an optional second crack phase. This phase intensifies the roast, resulting in a robust, full-bodied flavour profile. However, it's essential to strike the right balance to avoid over-roasting, which can lead to bitterness.
Cooling & quenching, resting & degassing
Once the desired roast level is achieved, the beans are rapidly cooled to halt the roasting process. This prevents the beans from continuing to cook and ensures that the flavours are locked in at their peak. During this phase, beans release carbon dioxide created during the roasting process, which needs to dissipate so as not to affect the coffee's flavour.
Science meets art
Roasting is where science meets art. Each step in the process requires precision and expertise, with roasters carefully orchestrating the transformation of green beans into a symphony of flavours. The next time you grab a cuppa, take a moment to appreciate the journey those beans have taken, from selection to roasting, to your cup, delivering that almost-perfect brew.