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Colombia is a country that produces many specialty coffees, and most of its coffee is still produced using the washed process. In this post, I will explain how to design a roasting profile for Colombian washed processed coffee. Here, you can apply this design method when roasting Colombia's major varietal coffees, such as Caturra, Castillo, Colombia, Tabi, etc.
When roasting a coffee for the first time, we should determine the speed of airflow required during roasting to fully bring out the coffee's flavors. The simplest way to find this out is to do two roasts. One with a fast airflow and one with a slow airflow, and we can easily find the answer.
To summarize briefly for your time, when we want to make a fast airflow inside our roasting machine, we can achieve this by opening the roasting machine's damper more, increasing the exhaust fan speed, and setting the gas higher. At this point, since we don't want the roasting time to be too short, I will lower the charge temperature to under 190°C to roast the coffee.
If we want to create a slow airflow in the roasting machine, we do the opposite setting. In that case, I will open the damper very little or lower the fan speed and set the gas low. If you're unsure about this explanation, please read my previous post, "The Importance of Airflow in Coffee Roasting"
Let's return to the experiment we are discussing in this post. I roasted washed coffee of the Caturra and Colombia varieties from the Cauca region of Colombia. As mentioned earlier, I roasted two batches with different airflow speeds.
I used the Giesen W1A for roasting here, and the roasting profiling software I used is Firescope. When using a Giesen roasting machine with Firescope, all the values that can be received from the roasting machine are neatly organized, just like you're looking at a chart. It's fully integrated with the controller and can be operated directly from a PC.
First, let me explain about Profile 1. In Profile 1, I intended to create a fast airflow within the roasting machine. Therefore, I set the gas of my Giesen roaster to about 50%, the Airflow pressure to 120Pa, and the drum speed to 60RPM. It's important to note that setting the gas this high and also setting a high charge temperature could significantly shorten the roasting time, so if you're targeting a light to medium roast level, it would be wise to lower the charge temperature.
For Profile 2, I set everything oppositely. Here, I set the gas of my Giesen roaster to about 30%, the Airflow pressure to 80Pa, and the drum speed to 58RPM. You can see the timing when I ramped down the gas by touching or hovering over the chart above.
When I tasted the coffee from Profile 1, I could feel the primary acidity of citric and malic acids with a medium intensity of sweetness, along with a fruit character and a relatively long aftertaste.
On the other hand, when I tasted the coffee from Profile 2, I felt an acetic acidity which I considered to be negative. The intensity of sourness and sweetness was low, and there was no fruit character. Instead, I felt woody and dry textures, leading me to think that the roasting was not successful.
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 (Profile 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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