Roasting Course with Coffee Lab

From September 2nd to September 9th, 2019, I took an intensive roasting course at Isabela Raposeiras’ Coffee Lab: a fusion between a coffee shop, roastery, and school. Coffee Lab is located in the neighborhood of Vila Madalena in São Paulo, Brazil.

The “cupping” process to evaluate our sample roast.

Marking my return to Brazil to study coffee, I got started rather quickly with an amazing opportunity to study roasting with a world-renowned specialty coffee shop. Roasting – in the context of coffee – is the process of turning the green coffee beans received from farms into the darker, brown beans that you are familiar with, the ones that are ready to be turned into a drinkable cup! This process is extremely technical and requires a lot of tests and consistency in order to develop a solid profile for a specific bean.

The six days were split up into three separate levels of two days. The school taught the material using a mixture of practical (actual roasting), theory, and cupping. The following information was covered:

Junior – Introduction to Quality Roasting

  • Basic operation of drum-styled roasters
  • Basic roasting theory (thermochemical reactions, phases, and sensory results)
  • Identifying roasting problems

Senior – Profile Development

  • Understanding of variables involved in profile development and associated sensory results
  • Development of profiles in relation to raw material availability and market context

Master – Coffee Blend Development

  • Sensory structure of a quality coffee blend
  • Roasting parameters for espresso and other methods
  • Buying raw coffee beans and identifying defects and problems

Disclaimer: This article is simply a reflection of my experiences in the course and also serves as a way to document my understanding of lessons learned. I am not claiming anything as fact or the way things should be done. The methods taught were ones used specifically by Coffee Lab, so it is very probably that other roasters use other methods. Additionally, the course was in Portuguese, so it’s likely I misunderstood some things here and there. This course was taught using a Diedrich roaster with a 5kg load.

Takeaway #1 – Taste, taste, taste!

No roast matters if you don’t taste the results in the cup to see what changed. Is there more body? Do you taste more acidity? Did the bitterness drop? Is it pretty flat? Lacking sweetness? You always have to test your roast’s results if you want to find the best profile for the coffee you are working with.

Isabela is a strong believer that in order to work in the coffee industry, you must taste coffee every day to become a good taster, capable of identifying different variables in a cup of joe. Is there a proper way to taste coffee? Why yes, yes there is, and I am going to discuss it before even getting into the process of roasting.

Cupping is a universally followed procedure developed with standardized protocols from the Specialty Coffee Association. First, the coffee is ground in equal amounts into five cups. Each person smells the coffee for its fragrance in this phase. Hot water is then added to the brim of the cup, and again each person smells the coffee and takes note of the aromas. After a certain amount of time, the crust of the coffee is then broken with a spoon three times (take note of aromas here as well), and the foam on top is scooped out to leave a cleaner cup for tasting… a process known as skimming.

As the temperature goes down, each person takes a spoon and starts tasting the coffee. One tests the cup for flavor notes, aftertaste/finish, body (or mouthfeel), acidity, sweetness, and uniformity/balance of the overall cup. One is supposed to slurp the coffee quickly – and usually loudly – into the mouth (there is a reason, but it’s lengthy and will be covered in another article).

The fragrance phase of the cupping process.

It’s important to taste the coffee at different temperatures. As it gets colder, our palates will be able to distinguish among more variables. When coffee is piping hot, that’s pretty much the only thing our senses recognize. It’s easier to hide defects and negative qualities with hotter temperatures. While tasting coffee cold can be a rather sad process, I learned a valuable comparison at Coffee Lab: tasting coffee cold is like seeing a person naked. You witness everything. If it’s an amazing coffee cold, then take that coffee (or person) home! It’s bound to be good!

Don’t forget to employ the method of triangulation. When comparing among different coffee samples, start with one cup, move to another one with a different level of acidity/sweetness/whatever, then return to the original cup. This will solidify your perception of the differences and make it easier to identify these variables in the future.

With all this being said, remember to roast samples, taste them via the cupping method, then roast again only changing one variable at a time. Taste the effects, and let the cycle repeat until you are satisfied with a profile.

Takeaway #2 – How a roaster works, simplified.

Before this course, all I knew was that green coffee beans went into this machine, stuff happened, and then they came out and were brown. Over six days, I learned to intricacies of what happens and how these things happen, which I will summarize below.

First, we turned the roaster on and let it warm up for 30 minutes. The temperature was fairly high, rising for a while until it started to slowly decrease. In this course, we waited until the temperature dropped to 170 degrees Celsius before dropping in the beans to start the roast. While the temperature was dropping, we measured 1kg of green coffee and set it in a bucket. At 171 degrees, we poured the bucket of green coffee beans into the loading bin at the top of the machine. Within a few seconds, the temperature dropped to 170 degrees, and we pulled a lever to drop the coffee into the rotating metal drum.

Coffee Lab’s roasts usually last from 9 to 15 minutes. During this span, we attempted to hit various benchmarks of temperature and time. We adjusted the size of the flame by letting in more or less gas, thus altering the temperature. Within the first couple of minutes, the temperature was still dropping until it reached a base temperature where it turned around and started to rise again. If we noticed the roast was going “too slowly”, we would turn up the gas and increase the flame. The contrary was also true.

Every minute, we recorded the time, temperature, and level of gas being used. Some roasters do this every 30 seconds, but Coffee Lab believes this results in all of your time being used to take notes instead of reacting to the roast and adjusting accordingly.

Once the target final temperature was reached (somewhere usually between 210 and 216 degrees), we opened the gate and let the coffee beans pour out onto the tray where they were rotated and cooled down.

A variable that we also had control over was the airflow. There were three settings: tray, medium, and drum. The standard setting of our roasts started with the airflow set to the tray, as to not blow hot air at the beans during the initial part of the roast and develop them too quickly. Once the “first crack” occurred (which sounds like popcorn), we switched the airflow to “middle”, with some hot air blowing into the drum and the rest blowing out into the tray. This helps clear out the smoke to make sure the flavor of the bean isn’t negatively affected. It also aids in preventing fires… a definite bonus! After releasing the beans into the tray, we adjusted the airflow to “drum” to suck the hot air away from the coffee beans in the tray and into the drum. Finally, we collected them into plastic bags and vacuum sealed them for storage!

Moments before being vacuum sealed.

That’s a very quick and basic run-through of how a roaster works on a basic level. Lots of different things going on at the same time require a high level of focus and quick reaction times. My professor compared roasting to driving… you must react to many different things going on at random moments. It’s good to have a general plan (like where you are going and when you want to arrive), but you must adjust accordingly and respond to other variables all the time.

So… what do changing all these variables actually affect?

Takeaway #3 – Every minor change affects the cup.

Whether you only roasted for 15 additional seconds or to half a degree higher temperature, every variation in a roast changes the final cup. Consistency is key. Once you have a developed profile for a specific coffee, you must stick to all the settings and keep each roast identical! This means the same roast time, initial temperature, final temperature, airflow settings, flame levels, amount of coffee, etc.

Seven roast samples of the same coffee to test different profiles.

The two main types of heat involved in our roasts were conduction and convection. Conduction heat refers to the heat transferred through contact of the coffee beans with the roasting drum. This is very important for developing sweetness and body in a profile. Convection heat refers to the heat obtained by heating the air. This is the most important heat of the process, resulting in at least 70% of the roasting. Coffee Lab generally starts with conduction heat in order to not dehydrate the beans too quickly. Since the sweetness of coffee is held in the sugars in the water of the beans, the longer this is developed, the more perceived sweetness a coffee will have in the cup (generally). Convection heat develops the beans faster than conduction, while only using conduction heat allows this development process to move at a slower rate.

Here are some tips to understand general effects from variations in the roast on the final cup.

  • Longer time: lower acidity
  • Shorter time: higher acidity
  • More conduction / less convection heat: more sweetness
  • More convection / less conduction heat: less sweetness
  • Too fast of a roast time
    • High acidity
    • Astringency (dryness) with notes of hay, jute, or peanut
  • Too slow of a roast time
    • Flavor and aroma can be dull
    • Lack of nuances, sweetness, and complexity
  • Very high final temperature: high level of carbonization, bitter and burnt taste
  • Very low final temperature: underdeveloped or raw qualities
  • To increase complexity (think acidity)…
    • Higher initial temperature
    • Lower final temperature
    • Shorter time
    • More convection heating (more air)
  • Airflow too high (lots of convection heat)
    • Dehydration of bean
    • Low sweetness
  • Airflow too low (lots of conduction heat)
    • Aftertaste of ash or smoke
    • Astringency (dryness)

As you can see, turning a green coffee bean into the perfect roasted bean is an extremely delicate process. Lots of trials and cuppings are required to develop a perfect, well-balanced profile for each coffee received. During this course, I learned that it wasn’t surprising for Coffee Lab to have 15 or more tests to develop a desired roast profile for a new batch of coffee. Crazy!

All in all, this was a very eye-opening and hands-on experience into the world of coffee roasting. I’m extremely thankful for such an amazing program and professors at Coffee Lab! My skills as a taster definitely improved, I know my way around a roaster, and I can successfully develop blends for espresso, among many other things. Cheers!

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