How Do Slow and Fast Roasting Change Yirgacheffe?

Japanese slow roasting and Nordic fast roasting reflect two different tasting goals: the slower style builds a rich, clean mouthfeel with rounded sweetness, while the faster style pushes bright acidity and lifted aroma. A sun-dried Yirgacheffe Worka Red Cherry lot brewed on both curves shows how airflow, heat and rate of rise decide the final cup.

Slow roasting gives high development and a short resting period, similar to braising meat until tender; fast roasting depends on hot-air efficiency and rewards high-quality green coffee beans. The Worka Cooperative and Banko processing plant supply the graded lot used for the comparison, and cupping results separate the two approaches by flavor orientation.

The two major schools of coffee roasting—Japanese slow roasting and Nordic fast roasting—reflect fundamentally different philosophies of tasting: the Japanese value a rich, clean mouthfeel, while the Nordic preference leans toward bright, elevated acidity and aroma. This time, Front Street Coffee selects sun-dried Yirgacheffe Worka Red Cherry and, through two actual roasting curves, compares the differences between slow roasting and fast roasting step by step—from airflow and heat adjustment, temperature rise rhythm, to the appearance of roasted beans and cupping performance. Slow roasting is like braising pork until tender, allowing heat to penetrate evenly, with a high degree of development, rounded sweetness, and a short resting period; fast roasting emphasizes hot-air efficiency and pursues lifted floral and fruity aromas, but places stricter demands on green bean quality. The article also introduces the origin background of the Worka Cooperative and the division of labor model of the Banko processing plant, and, combining green bean grade, appearance consistency, and actual cupping results, sorts out the applicable scenarios and flavor orientations of the two roasting methods for coffee lovers’ reference.

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When it comes to schools of coffee roasting, the most frequently mentioned are probably Japanese slow roasting and Nordic fast roasting.

Front Street Coffee has learned that the roots of these two roasting methods can roughly be traced back to two completely different orientations in coffee tasting—the Japanese care more about mouthfeel, while the Nordic people emphasize aroma more; Japanese palates do not readily accept acidity and are especially sensitive to astringency and off-flavors, so their coffee stresses cleanliness and richness; whereas in the Nordic region, because of the cold climate, people prefer sweet-and-sour tonality and also pay more attention to aroma expression (no wonder their noses are quite high). The bean we selected this time is Yirgacheffe [Front Street Worka Red Cherry Coffee], processed by the sun-dried method.

From this, the fundamental difference between the two roasting methods can be understood—slow roasting is like braising pork until tender, then reducing the sauce at the end, with good development, prominent sweetness, and a rounded mouthfeel; fast roasting is like searing a steak, first using high heat to create a charred exterior and tender interior, then turning to low heat to let the inside develop, allowing the coffee to develop fully and pursuing floral and fruity aromas.

The above are all “theories” circulating among enthusiasts, so today let us actually put them into practice and see how slow roasting and fast roasting differ in technique and flavor presentation…

Introduction:

Within Worka village there are quite a few green bean processing plants, including both cooperatives and private companies. Banko Factory is closely connected with Worka Coop. Because the cooperative’s processing plant cannot digest at one time the amount of freshly harvested cherries collected during the same period, the smallholder coffee farmers of Worka Cooperative can choose a nearby green bean processing plant—that is, Banko Factory—to share and complete the processing.

The total planted area of family members of the Worka Coop smallholder coffee farmers is about 763 hectares, with annual output reaching 460 tons. The average coffee planting area of these smallholders is about 1 hectare, at an altitude of about 1,850 to 2,100 meters, with varieties mainly consisting of Heirloom. The average output of each smallholder is about 650–700 kg per hectare. The main local production model is: small coffee farming households send the red cherries harvested in each lot directly to the cooperative’s processing site for unified processing.

This batch of green coffee beans comes from the Worka Cooperative, uses the sun-dried processing method, and has been rated by ECX as the highest grade, G1. From the appearance, consistency, and freshness of the green beans to the dry aroma and flavor performance, all are noteworthy and possess the origin characteristics of Yirgacheffe.

Next, let’s look at our two roasting curves.

The first is slow roasting. By adjusting airflow and heat, the temperature rise is kept on a relatively stable rhythm: airflow is adjusted all the way from 20% to 80%, and at the same time, in order to ensure a steady temperature rise, heat is increased by 10% at the turning point to compensate for the heat taken away by exhaust, so that first crack can be heard proceeding in an orderly manner.

Then there is the fast-roast batch. We first started with a lower bean charge temperature, set the heat relatively high at the beginning, and maintained airflow at 80% before first crack, emphasizing hot-air efficiency to simulate the environment of a European-style roaster. As shown in the figure, the turning point was faster than in the previous batch, and the temperature climbed rapidly in the early stage. By reducing heat step by step at the turning point, browning point, and first crack point, the development time of the Maillard reaction was extended, and the ratio of development time to total time was relatively large.

From the appearance of the roasted beans, the slow-roasted beans are relaxed and relatively uniform in color. After grinding, the slow roast has less color difference, while the fast roast has a more obvious color difference.

Cupping comparison:

Finally, a summary: from the appearance of the roasted beans and the cupping results, it can be seen that Japanese slow-roasted coffee has better overall consistency, a steadier mouthfeel, and is also a bit sweeter, smooth on entry, with more prominent caramelized flavors; although Nordic fast roasting is slightly inferior in appearance, the first sip is floral and fruity, with a slight tea-like quality, and the aroma is more lifted. As far as green beans are concerned, Nordic fast roasting places higher demands on green bean quality, because if this roasting method is not handled properly, it will magnify the beans’ flaws even more; Japanese slow roasting has relatively looser requirements for green beans, and coffees such as Mandheling are especially suitable for slow roasting to amplify their strengths. Because slow roasting allows heat to enter the bean core evenly, the degree of development is high, so the resting period is shorter. The editor has tried drinking it as soon as 2 hours later, with no dryness at all; and just as a good steak needs to be rested and aged to taste its best flavor, fast roasting has a relatively longer resting period, but once resting is complete, the aroma at the moment of grinding can make one feel refreshed and delighted.

As for shaping coffee flavor, different roasters have their own understandings, so there is no standard answer. The above is only the editor’s humble opinion on roasting; please point out any shortcomings.

Front Street Coffee believes that a good cup of coffee comes from the coffee farmer’s careful cultivation, the processing plant’s meticulous processing, the roaster’s artisan roasting, and the barista’s precise operation. What finally reaches your taste buds is that pleasant richness and aroma.

The above content is compiled by CoffeeHunters, a coffee news website.