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Designing Profiles Based on Roast Levels - Dark Roast

By
Sungbin Cho
January 7, 2024
6
min read
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In continuation of the previous article on "Roasting Profile Changes Based on Exhaust Temperature," this post delves into the details of dark roasting profiles emitted after the 'start of the second crack' as the exhaust temperature rises.

  • Roasting Profile Changes Based on Exhaust Temperature (feat. Guatemala Washed Coffee)
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In the previous article, the importance of adjusting the profile as the exhaust temperature rises was emphasized. However, simply extending or shortening the profile without adjusting settings such as heat supply, exhaust, and input temperature can lead to negative outcomes.

To avoid results like 'baked' defects, it is crucial to consider the airflow during roasting, especially concerning the exhaust temperature. Gradual adjustments to the airflow, proportionate to the rise in exhaust temperature, are recommended. In addition, raising the input temperature and shortening the roasting time contribute to a more balanced process.

This article focuses on scenarios where the exhaust temperature rises further, leading to emission after the 'start of the second crack.' The approach aligns with the previous profile adjustments but emphasizes even slower airflow settings to design an effective roasting profile.

When designing dark roasting profiles, one must be cautious of 'baked' defects, especially 'burnt' defects. Targeting higher exhaust temperatures with minimal moisture content may result in 'baked' defects, including 'burnt' and 'scorched' characteristics. To prevent these defects and achieve a dark roast successfully, favor 'low heat' with appropriate exhaust and high input temperature settings to create a 'slow airflow.'

Example Profiles:

Profile 1:

  • Roasting Machine: Easyster 1.8 (2021)
  • Batch Size: 1,000 g
  • Exhaust Amount: 840 g
  • Weight Loss Rate: 16.0%
  • Roasting Point: Emission after an approximately 21-degree temperature rise post the start of the first crack (1-degree rise after the beginning of the second crack).

India Gangagiri coffee beans were used for Profile 1, aiming for a 'light to medium' roast. The unique slow airflow in this profile results in high body, sweetness, cleanliness, and a blend of acidity and character.

Profile 2:

  • Roasting Machine: Easyster 1.8 (2021)
  • Batch Size: 1,000 g
  • Exhaust Amount: 826 g
  • Weight Loss Rate: 17.4%
  • Roasting Point: Emission after an approximately 25-degree temperature rise post the start of the first crack (3-degree rise after the beginning of the second crack).

Colombia Natural 50% + Colombia Washed 50% Blend coffee beans were used for Profile 2. The airflow was slowed down further, achieving a slightly higher exhaust temperature, resulting in an intensified dark roast with a minimal risk of defects.

Profile 3:

  • Roasting Machine: Easyster 1.8 (2021)
  • Batch Size: 1,250 g
  • Exhaust Amount: 1,025 g
  • Weight Loss Rate: 18.0%
  • Roasting Point: Emission after an approximately 27-degree temperature rise post the start of the first crack (7-degree rise after the start of the second crack).

Colombia Washed 50% + Colombia E.A. Decaf 50% Blend coffee beans were used for Profile 3. With an increased batch size, higher heat supply, exhaust, and input temperature, this profile showcases a versatile dark roast with a careful approach to prevent defects.

In conclusion, adjusting roasting profiles based on exhaust temperature, especially for dark roasts, demands careful consideration of airflow and temperature settings. The examples provided offer insights into achieving consistent and high-quality dark roasts.

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Sungbin Cho
CMG Coffee Bar Head Roaster, Wecoffee Education Manager
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