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Into the Eye of the Roastmaster

Into the Eye of the Roastmaster

What’s going on in that roaster? A lot more than you might think.

If you’ve ever tasted a green coffee bean, you know there’s no trace of those chocolate and fruit flavors that we have come to adore in specialty coffee. Those flavors are developed throughout the roasting process as the roastmaster manually adjusts heat and air flow.

So I’ve sat down with one of our roastmasters, Douglas Wray, to find out what makes a great roast!

While you might be thinking your roastmaster is just sitting there waiting for a roast to complete, he/she is actually monitoring the roast very carefully and making adjustments, “[relying] on sounds, colors, and smells, because of changes in the properties from raw coffee to cooked coffee.” Roastmasters are assisted by computers that are making calculations and rendering graphs based on real-time readings from probes within the roasting drum. “Achieving a particular rhythm of the roast is the essential goal” Douglas tells me.

Before the roaster is turned on the roastmaster is already weighing his options. As Douglas points out that, “at the very outset is the question of how-much-coffee is added to how-hot-of-a-machine? This will have a huge impact on how much power you are working with in the roast.”

The first stage of roasting is the drying stage. Coffee beans, however hard and chalky seeming, still contain some water; generally somewhere around 8-12% humidity. This stage can take anywhere from 4-8 minutes in a drum roaster, depending on the density, size and humidity of the bean. During this stage the roaster is just warm enough to dry out the beans without scorching them. This stage is endothermic (i.e. the beans are collecting energy.)

During this stage the beans are still releasing the last bits of water as vapor.

"A few minutes later (about half way through roasting), the coffee dries and a quick color change indicates the onset of the Maillard reaction.  The smells emitted by the beans changes dramatically as sugar development begins,” Douglas eagerly tells me.

The Maillard reaction is responsible for the visible browning that takes place. Sugars and amino acids react with one another to form polymeric compounds which act as brown pigments (melanoidins) giving the bean its final color. The roast generally will slow down during this stage on its own and with the guidance of the roastmaster. During this stage heat and airflow are adjusted to encourage flavor development. Signaling the end of the browning stage is when, what roastmasters refer to as First Crack takes place.


“The roaster must be careful not to rush through first crack and also must be careful not to lose control and power.” How a roaster controls a roast through First Crack is paramount to achieving the intended flavor profile. 

The coffee starts to pop and you can hear it happening. Douglas equates this to popping popcorn, saying, “it is a tiny explosion of gasses rushing out of the beans that spreads to each bean one by one.”

This signals the beginning of the development stage. This is where all that energy that’s been slowly bottling up in each bean is released.This stage is short, usually 15-25% of the entire roast time depending on the intended roast degree and flavor profile.

Matching a coffee to the right roast style is paramount to producing a coffee’s ultimate flavor. There are two main components of a roasting style: Roast Degree and Total Roasting time.

Roast Degree

The importance of reaching a target end temperature of a roast is something most folks understand. This is where the differing roast degrees come from ie. light, medium, dark.  At the end of a roast, coffee is over 400°F and the final temperature has an immense effect on the flavor profile of the final cup. Slight variances in final temperature produce vastly different beverages. "A difference of just 5°F is akin to a 5 Mile walk down the road," DOuglas elucidates emphatically.

Typically light roasted coffee is more acidic, and dark roasted coffee is more bitter. Fruity notes are also more common in light roasts, and roasty and burnt flavors are more common in dark roasted coffee. Light roasted coffee is more fruity due to high amounts of an organic compound, 5-hydroxymethylfurfural. When roasting goes further, this compound breaks down to less fruity compounds. The amount of sulfuric compounds increases, which produces roasty and burnt flavors.

Total Roast Time

Even though roast degree has the biggest role on coffee’s flavour profile, total roast time and time of each stage are also important factors. If you roast fast, you will get more desired aroma compounds. Coffee’s total flavour (fruity, berry-like, chocolatey, nutty altogether) is stronger. Also the amount of aroma compounds, which are created in the beginning of development stage, is higher with fast roasting.

Fast roasting enhances all the flavours of the coffee. If we do not want some flavours in the coffee, we need to adjust the roast profile. For example, acidity is normally desired flavour but in espresso blends people often prefer a less acidic profile. When roasting slower organic acids have more time to break down, the coffee becomes less acidic. This is where slow roasting has its place.

So, how does the roastmaster go about deciding on the roast style for a particular coffee?

As Douglas tells me, there’s many factors at play and when I asked him this very question, here’s what he had to say:

“This is the most fun question we approach. Roasting a coffee must consider the varietal of arabica, the altitude and growing conditions, the processing style that removed the cherry fruit, and the age and moisture content.  These, and a myriad other factors, will determine the potentials that the coffee contains.  Equally important is the question of "what are we trying to accomplish with this coffee?”  For example, where is this coffee going on the menu?  Is it a single origin coffee or is it destined for blending?  Does our menu need something more fruity or more chocolaty?  What are our customers seeking?  Some coffees are very versatile and are compatible with a number of different roast styles, while others have a thin window of greatness.”

So why go through all this effort? Why artisanal roast in the first place? Well, it’s more than just seeking out the best flavor—I’ll let Douglas take it from here:

“Sustainably produced coffee has a healing effect on the environment it grows in. Specialty coffee prefers to grow in the tropics in a rain forested canopy and other shade trees, with fauna providing the pest control and flora providing nutrients to its soil.  Basically, it prefers biodiversity. Artisanal roasting is the responsibility of unlocking the amazing potential that farmers have provided in their coffees. Meticulous attention to the roasting process is necessary to honor the efforts that come before and after the roaster.  Together, as a community, we make great coffee.  Artisinal roasting is one of many pieces of the coffee process that are necessary to allow the world’s best coffees to shine.

At Coffee Labs Roasters we understand that a commitment to sustainability is not just an ethical choice, it is necessary for producing beautiful coffees. Both the economic and agricultural processes of coffee production make delicious beverages when they are responsibly driven. The crop prefers it.  Coffee farm workers need it. We connect directly with our coffee producers to ensure we are bringing the best possible coffee to Tarrytown. Thereafter, we are coffee people because we are food people: we know how to cook and we make every effort to understand the desires of our customers. Our roasters produce award winning coffees and our professional baristas are skilled at competition level.  We do this because we love it.”

‘Nuff said.

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