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Learning About Medium Point Roasting of Colombian Washed Coffee

By
Sungbin Cho
February 1, 2024
7
min read
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This article follows the previous two parts, "Designing a Light Roast Profile - Colombian Washed (1)" and "Designing a Light Roast Profile - Colombian Washed (2)" In this post, we focus on the medium roasting point, defined as the range between the end temperature of the first crack and just before the start temperature of the second crack.

Medium roasting requires a gradual decrease in airflow as the drop temperature increases, compared to the light roasting profile. This means the heat should be lower, and the charge temperature should be higher. The exhaust speed should also decrease proportionally to the reduced heat. Overall roasting time should also be gradually shortened. Failing to do so and simply increasing the drop temperature with a light roasting profile may result in a baked defect.

Medium roasting, having a higher drop temperature than light roasting, might not make flavor development overly difficult. However, issues such as excessive acidity, roastiness, dryness, or a short finish can occur, indicating a baked defect. Baked defects are often more noticeable than underdeveloped ones in roasting.

Next, we present examples and modification methods for medium roasting coffee profiles. Here's the coffee information used in this part of the series:

  • Coffee: Colombia Antioquia Cerro Bravo Washed
  • Region: Cerro Bravo, Antioquia
  • Varietal: Castillo, Colombia
  • Growing Altitude: 1,450 m - 1,800 m
  • Process: Washed

Profile 1 - Colombian Washed Roasting with a Baked Defect

  • Roasting Machine: Giesen W1A (2020)
  • Charge: 1000 g
  • Drop: 835 g
  • Weight Loss: 16.5%
  • Roasting Drop Point: About 13°C (55.4°F) rise in temperature after the start of the first crack

The roasting in Profile 4 results in baking. The character is sufficiently recognized during cup tasting, but the acidity is high, and the roasty aroma is overly pronounced. Therefore, the cup is unbalanced at all temperatures. The acidity should be slightly reduced, and the roastiness should be decreased to the expected level at the targeted drop temperature. The flavors, apart from the defect, are mainly citric and malic acidity with orange and red apple aromas, brown sugar character, and syrupy.

Compared to light roasting, the intensity of the heat during roasting is higher for medium roasting. Lowering the heat and forming a slower airflow can positively resolve baking. If adjusting Profile 4 to the same drop temperature, set the heat slightly lower (about 10%p~20%p). If aiming to increase the drop temperature by about 2°C-3°C (3.6°F-5.4°F), set the heat lower (about 20%p) and increase the charge temperature (about 10°C/18°F). If aiming to decrease the drop temperature by about 2°C-3°C (3.6°F-5.4°F), set the heat slightly lower (about 10%p) and decrease the charge temperature (about 10°C-20°C/18°F-36°F).

Profile 5 - Resolving the Baked Issue with Profile 4

  • Roasting Machine: Giesen W1A (2020)
  • Charge: 1000 g
  • Drop: 838 g
  • Weight Loss: 16.2%
  • Roasting Drop Point: About 15°C (59°F) rise in temperature after the start of the first crack

The roasting in Profile 5 is well executed. Following the second baking resolution method of Profile 4, the drop temperature was targeted to be about 2°C (3.6°F) higher, with heat set 20%p lower and charge temperature increased by 10°C (18°F). The cup is balanced at all temperatures with clear character, medium intensity acidity, and the rich toastiness expected at the higher drop temperature.

Profile 6 - Colombian Washed Roasting with a Baked Defect

  • Roasting Machine: Easyster 1.8 (2021)
  • Charge: 1000 g
  • Drop: 852 g
  • Weight Loss: 14.8%
  • Roasting Drop Point: About 13°C (55.4°F) rise in temperature after the start of the first crack

The roasting in Profile 6 results in baking, similar to Profile 4 but with an additional rubber-like aroma. The heat was set a bit high, and the charge temperature was slightly lower compared to the drop temperature. Reducing the heat and increasing the charge temperature to form a slower airflow can positively resolve baking. If adjusting Profile 6 to the same drop temperature, set the heat slightly lower (about 10%p15%p) and increase the charge temperature (about 10°C/18°F). If aiming to increase the drop temperature by about 2°C-3°C (3.6°F-5.4°F), set the heat lower (about 20%p) and increase the charge temperature (about 20°C-30°C/36°F-54°F). If aiming to decrease the drop temperature by about 2°C-3°C (3.6°F-5.4°F), set the heat slightly lower (about 5%p10%p).

Profile 7 - Resolving the Baked Issue with Profile 6

  • Roasting Machine: Easyster 1.8 (2021)
  • Charge: 1000 g
  • Drop: 855 g
  • Weight Loss: 14.5%
  • Drop Point: About 10°C (50°F) rise in temperature after the start of the first crack

The roasting in Profile 7 is well executed. Following the third baking resolution method of Profile 6, the drop temperature was targeted to decrease by about 2°C-3°C (3.6°F-5.4°F), with heat set at 0.06kPa (about 5%p) lower. The cup is balanced at all temperatures with clear character, medium intensity acidity, and appropriate toastiness.

Generally, medium roasting benefits from slower airflow than light roasting and faster than dark roasting. If a slight baked defect is observed, as in Profiles 4 and 6, the heat setting is often a bit high. Therefore, in cases of baking, reducing the heat and increasing the charge temperature often resolves the issue. If underdeveloped, the heat setting is usually low, and airflow is formed slowly. Increasing the heat and lowering the charge temperature often resolves this.

This article explored the roasting of Colombian Washed coffee. Settings for batch size, heat intensity, exhaust speed, and drum speed during roasting are all important. Essentially, understanding the airflow formed by the balance of heat intensity and exhaust speed is crucial for effectively raising the temperature of the green beans and achieving the desired flavor profile. Understanding airflow formation naturally leads to determining the appropriate charge temperature.

Especially for Colombian Washed green beans, which require fast airflow, the degree of airflow formation varies depending on the drop temperature, making it initially challenging to create detailed profiles. Keeping detailed records of profile progression and sensory evaluations to build data will help in designing and adjusting profiles.

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Sungbin Cho
CMG Coffee Bar Head Roaster, Wecoffee Education Manager
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