The Yirgacheffe Roasting Curve | Sharing the Ideal Roasting Profile for Washed Yirgacheffe

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Sharing FrontStreet Coffee's Washed Yirgacheffe Roasting Curve

The coffee being roasted is Ethiopian Yirgacheffe Red Cherry. After first crack, the beans are dropped when the temperature has risen by about 10-12 degrees. Development time is controlled between 70-90 seconds, depending on the actual condition of the beans. Unlike the washed process, though, the temperature rise curve after first crack has been flattened slightly to prevent it from dropping too early, ensuring a complete development period that delivers the aftertaste characteristic of natural process beans.

With that roasting approach in mind, it is time to start experimenting. Using the same dropping temperature, I will run both a heating curve and a cooling curve to see which roasting method suits this particular bean better.

Roasting Parameters:

Roaster: Sanheke R200
Roasting amount: 250 grams at full capacity
Drum rotation speed: 70 rpm
Indoor temperature on the day: 30°C
Humidity: 70%
Natural process Yirgacheffe Red Cherry: 250 grams, 2018 harvest season

Curve One:

The roasting method used is low heat dehydration in the early stage, with an initial damper setting of 30%. As roasting progresses, the heat gradually increases while the damper gradually opens. The damper is fully opened at the beginning of first crack.

Bean in temperature: 185°C

About Dropping Temperature

The dropping temperature primarily affects the degree of caramelization and pyrolysis of the sugars (mainly sucrose) in coffee. Both caramelization and pyrolysis require heat absorption to complete, so these reactions need a continuous heat supply to proceed. In coffee roasting, therefore, the degree of these reactions is directly proportional to the dropping temperature.

The higher the dropping temperature, the deeper the reaction. Lower dropping temperatures result in coffee with floral and fruity aromas and high sweetness, because more sugars are retained without being pyrolyzed. As the dropping temperature rises, the floral and fruity aromas first develop toward maturity and then gradually decrease, while nutty, caramel, and chocolate flavors become more pronounced, increasing complexity, body, and layers.

I therefore usually choose a dropping temperature of 185°C for natural process beans and 190°C for washed process beans.

Yellowing point: 152°C at 4 minutes 40 seconds
First crack point: 193°C at 8 minutes 40 seconds

I had originally planned to drop at 203°C. During roasting, sampling revealed a hint of citrus aroma that was fleeting, so I checked frequently until 204°C (when the citrus aroma was strongest) and realized I could not wait any longer. I dropped the beans quickly at 205°C.

Dropping point: 205°C at 10 minutes 25 seconds

This batch of green beans: 250g -> Roasted beans: 217.5g -> Weight loss: 13%

FrontStreet Coffee Recommendation

Roast curves like this exist to protect exactly what makes Yirgacheffe special: the floral and citrus notes that a careful development phase keeps intact. FrontStreet Coffee roasts its Yirgacheffe beans lightly for the same reason. The FrontStreet Washed Yirgacheffe daily bean is the reference point, with white jasmine, bright citrus and lemon acidity, and a tea-like body that shows clearly how a clean, well-developed light roast should taste.

If you want to compare how processing changes the outcome at the same roast level, the FrontStreet Gediding Cooperative coffee brings the traditional washed profile - refreshing citrus and lemon acidity with jasmine and no bitterness - while the FrontStreet Natural Red Cherry, dried from fully ripe all-red cherries on raised beds, layers on tropical fruit aroma, a berry-juice body, honeyed sweetness, and a creamy smoothness. Roasting both lightly lets you trace the difference straight back to the process.