Achieving a positive expression of coffee character and flavor during the transition from green beans to roasted beans is crucial in the roasting process. To accomplish this, a roaster must accurately understand the characteristics of the green beans and design an appropriate roasting profile by setting the desired roasting exit point.

Importance of objective sensory judgment:To produce superior results, roasters benefit from a wealth of roasting profile data, including objective sensory judgments. The temperature log graph provides a plethora of interpretable information. However, interpreting this data can be challenging, especially for those new to it, due to either insufficient interpretation or misinterpretation.

Meaningful interpretation of the temperature log graph and its utilization requires comparing positive and negative data from roasting outcomes. It is advisable to conduct multiple trials and statistically compare the results rather than concluding a limited number of data points (1-2 trials). Efforts in this direction help interpreting multiple roasting data sets accurately, increasing the volume of interpreted information. Therefore, the use of the "Firescope" log program is essential for recording, storing, and closely comparing data for effective utilization.

Roasting profile design for Ethiopian natural coffee - Part 1:Let's begin the exploration of roasting profile design for Ethiopian natural coffee. The initial step involves understanding the physical characteristics of green beans. It is essential to determine whether the green beans require the formation of a rapid or a slow airflow during roasting. This can be achieved by roasting two batches—one with fast and another with slow airflow.

Refer to the previous post, ‘Factors Influencing Airflow in the Roasting Process,’ for information on creating fast and slow airflows.

The coffee chosen for roasting is Ethiopia Yirgacheffe, Konga region, Heirloom variety, naturally processed beans. Two batches were roasted with different airflow formations. Figure 1 represents roasting with a relatively fast airflow, while Figure 2 represents roasting with a relatively slow airflow.

In Figure 1, the roasting with a relatively fast airflow (higher heat, higher damper, faster fan speed, lower input temperature) results in an overall light body. Fruit aroma is briefly present but lacks endurance, dissipating quickly. Nutty flavors and a rough texture overshadow the character, with negative defects primarily perceived as papery and straw-like.

On the other hand, Figure 2, representing roasting with a relatively slow airflow (lower heat, lower damper, slower fan speed, higher input temperature), exhibits rich positive aromas of berries, peach, and floral notes. Simultaneously, the body is medium to high.

Selecting the positive type:Choosing the batch with a positive impact on coffee character and flavor among the two roasting profiles, the roaster refines the profile accordingly. In this case, the slower airflow in Figure 2 was deemed positive. To achieve even better results, further batches can be conducted, refining the profile based on the slow airflow approach.

Efforts to record and analyze:By collecting and repeating roasting profile data, especially when the origin and processing methods are the same, one can omit the step of testing two batches with different airflows. Even without conducting this step, it is possible to predict which approach—fast or slow airflow—is likely to yield positive results.

In the previous installment, ‘Roasting Profile Design for Colombian-Washed Coffee - Part 1,’ roasting with a fast airflow was deemed positive. In contrast, for Ethiopian natural coffee, roasting with a slow airflow is considered positive, opposite to Colombian washed coffee.

In the next batch, we will continue with roasting Ethiopian natural coffee using a slow airflow, incorporating sensory judgments and feedback to further refine the profile.