Introduction to Coffee Roasting Class at Commune

How does coffee go from green to brown? We learn the basics.

by Lendl Klein

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The Coffee Crawl Series team was lucky to be invited to one of the coffee roasting classes at Commune. It was held last February 9, 2019 at Commune Cafe and Bar in Polaris corner Durban Sts. Poblacion, Makati.

There are around 12 participants, raging from coffee brewers up to entrepreneurs and farm owners who all have the same goal: to understand how the whole roasting process works and how to do it.

The master roaster, Lyndon Realubit (IG: @lyndonreal), taught the class the basics of roasting and what to look out for in doing so.

So, what is roasting?

Roasting is the systematic application of heat at different times to create aroma development.

But it is more than just applying heat – it is an art and science combined. “You have to know what you are doing. You have to experiment, know your beans, the types of heat, your roasting machine, the air flow,” as Lyndon stated.

There are lots of factors to consider in the roasting process. First, the green beans need to achieve a certain moisture content level, around 9% to 13%. Lyndon recommends that the ideal moisture level is around 10% to 12%.

“The drier the bean, the easier it gets roasted. Too dry and it will roast very fast. Too moist and it will be hard to roast.”


Stages of Roasting

Drying Phase

This stage is where the leftover moisture in the green beans are removed. Drying is important because this is the first part where the beans absorb the heat from the roasting machine; at this point the water in the beans dry out, and some acids are removed.

Maillard Reaction

Sugar, carbohydrates, amino acids, react with heat. This is where the browning of the beans begin. The interaction of sugars and acids due to high temperature of the roasting creates different complex aromatic compounds – a very pleasant experience when smelled!


This is where the first crack (literally beans making a cracking sound) and flavor development happens. The roaster can make tweaks in order to achieve a certain profile of the coffee at this point.

Cooling Phase

After roasting, the beans are transferred into a cooling tray and is cooled for 3-4 minutes. This is important as coffees still roast even if already outside the machine, and it needs to be cooled fast enough as heat retained in the beans will destroy the flavor created from the roast.

Actual Roasting Activity

After the primer discussion about roasting, it was now the participants’ turn to roast using the Probat roasting machine of Commune

Participants were divided into two groups, and each were asked to monitor the duration of the roasting, the times, and the specific temperatures that come with it.

The participants were excited when they heard the faint first crack as the coffee is being roasted, and Lyndon explained what is happening in that roasting phase.

Air Flow and Heat Transfer

Air flow through is just as important as the heat from the roasting machine. 

“Roasting is mostly about force convection… normally, good drum roasters have 75% convection and 25% conduction.”

The heat transfer through air flow (convection) and the heat produced by the roasting machine itself contributes to the outcome of the coffee. The softer the bean density, the lower the air flow should be.

To Sum it Up

There are a lot of factors involving coffee roasting: the air flow in the roasting, the heat retention in the drum, the freshness of the green bean, its density, and the moisture content. But the most important is the raw material itself – the unroasted coffee. No matter how great the roasting machine or how experienced the roaster is, if the coffee is low in quality the outcome will only be as good as it gets.

Interested in learning more about coffee roasting? Commune offers roasting classes quarterly! You may check out their website for more information
about their events.

Pie chart image from Barista Camp 2015 | Maxwell Colonna-Dashwood – Water chemistry


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Introduction to Coffee Roasting Class at Commune