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This post is a continuation of the roasting Ethiopian natural coffee series, 'Roasting Profile Design for Ethiopian Natural Coffee Part 1' and 'Part 2'.Previously, I discussed various indicators observed in the roasting profiling chart. Through numerous roasts in my setup, I've identified indicators that yield positive results for Ethiopian natural coffee. Naturally, having more roasting profiling data makes it easier to find these indicators. However, if the coffee has physical exceptions, there can be factors that cause the main indicators to deviate from the average.
A roasting expert who deeply considers the process can quickly identify and resolve issues caused by unique conditions in green coffee during roasting. However, roasters who have not collected or properly analyzed roasting profiling data may attribute these issues to coffee quality problems or may not be able to discover the positive flavors in the coffee.
In this post, we will not design the profile based on sensory evaluation, marking it as positive or negative. Instead, we will explain the changes in the roasting profiling chart due to exceptional coffee characteristics and focus on roasting techniques that guide it back to a standard roasting progression.
The baseline profile represents a typical roast for Ethiopian natural coffee, where various indicators are close to the average, and the coffee's positive flavors have been developed. This profile serves as the background for comparison with the profiling chart examples that are presented later.
<Baseline Profile>
We will discuss the following four example cases:
The following green coffee corresponds to the case of smaller than average screen size: Ethiopia Guji Uraga Goro Muda Natural, from Uraga Woreda, Guji, Oromia, by Goro Muda, Welichu Wachu W.S. It's an heirloom variety grown at an altitude of 2,228 meters (7,310 feet) and naturally processed.
<Profile 1>
Comparing <Profile 1> to the <Baseline Profile>, <Profile 1> shows a generally higher BT and ET temperature during the same time frame. In my environment, a positive BT RoR (60s) peak value is targeted between 23.0 - 24.9, but it reached a higher value (26.0), indicating a faster temperature rise in the early part of the roast. This often results in a lower BT RoR value around the start and after the first crack, affecting other indicators to deviate from the positive average.
To bring the unique indicators back to the positive average, <Profile 2> was conducted as follows:
<Profile 2>
In the progression from <Profile 1>, the airflow speed was almost unchanged, and the charge temperature was slightly reduced (by 10°C or 18°F). The BT RoR's peak value decreased and most of the main indicators proceeded similarly to the <Baseline Profile>, leading to a positively predicted profile.
In the next part, we will continue with "2. The first crack starts at a temperature 3°C (5.4°F) higher than usual."
