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Designing a Light Roast Profile - Colombian Washed (1)

Sungbin Cho
July 24, 2023
min read
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In order to achieve successful coffee roasting, we need to bring out positive coffee characteristics and flavors. To do this, the roaster must understand the characteristics of the coffee beans and design a roasting profile that aligns with the intended roasting discharge temperature.

Roasters need to accumulate the results of roasting progress and sensory evaluations to determine whether the roasting was successful or not. This collected statistical asset becomes valuable for roasters. With statistical roasting data, It becomes more easier when you design the best profile for new crop coffees.

Therefore, it is essential to develop habits of collecting and analyzing roasting data and recording sensory data. In this regard, using the roasting profile monitoring, data collection, and management solution software “Firescope” can be of great assistance in achieving successful roasting outcomes.

To begin designing the roasting profile for washed processed green coffee beans of Colombian varieties such as Caturra, Castillo, Colombia, and Tabi, here is an explanation:

The key approach to understanding the main characteristics of the green beans during roasting is to conduct roasting using two different methods: fast airflow and slow airflow. The goal is to determine when the flavors and characteristics of the coffee beans are best expressed.

In a previous post titled "Factors in Roasting Process that Influence Air Flow," we explained the methods of roasting by forming fast and slow airflow.

For this roasting experiment, we used washed processed coffee beans from the Caturra and Colombia varieties grown in the Cauca region of Colombia. We conducted two separate roasting batches, each with a different airflow speed, to observe and understand how the flavors are affected.

Chart of Colombian washed coffee roasted with fast airflow
<Figure 1> Chart of Colombian washed coffee roasted with fast airflow
chart of Colombian washed coffee roasted with slow airflow
<Figure 2> Chart of Colombian washed coffee roasted with slow airflow

In the roasting with relatively fast airflow (<Figure 1>) compared to slow airflow (<Figure 2>), using higher heat, faster fan speed, and lower input temperature, the coffee exhibits a moderate intensity of citric and malic acidity, along with a pleasant sweetness and fruity character in the aftertaste.

On the other hand, in the roasting with relatively slow airflow (<Figure 2>) compared to fast airflow (<Figure 1>), using lower heat, slower fan speed, and higher input temperature, the coffee shows lower intensity of sourness and sweetness, and the fruity character becomes less prominent. Instead, negative attributes like woody and dry notes are more pronounced.

Thus, by selecting the roasting profile that positively expresses the desired coffee character and flavors, and then adjusting the specific variables, the overall quality of the final product can be improved. In this particular Colombian washed coffee sample batch, the roasting with fast airflow (<Figure 1>) showed positive results. However, it's not the best profile, so adjustments will be made in the next roasting batch. During the next roasting, variables such as input temperature, initial heat, and discharge temperature will be adjusted based on the nuances perceived during cupping.

Interpreting metrics like BT, ET, and RoR graphs, as well as considering post-roasting indicators such as weight loss, color, moisture content, density changes between green and roasted beans, and sensory evaluations, will help in adjusting factors like heat, exhaust, input temperature, drum speed, batch size, and more. Further details about profile design will be covered in future posts. Accumulating data throughout this process can be immensely helpful when roasting new batches of green coffee.

In conclusion, based on the data we have tested, washed processed coffee beans of major Colombian varieties such as Caturra, Castillo, Colombia, and Tabi (with some exceptions like Geisha and Bourbon) require roasting with relatively fast airflow. Apart from dark roasts initiated after the second crack, attempting to maintain a generally faster airflow throughout the roasting process would be beneficial.

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Sungbin Cho
CMG Coffee Bar Head Roaster, Wecoffee Education Manager
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